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Testing a Trio of Canon RF Zoom Lenses for Astrophotography 


In a detailed review, I test a “holy trinity” of premium Canon RF zoom lenses, with astrophotography the primary purpose.

In years past, zoom lenses were judged inferior to fixed-focal length “prime” lenses for the demands of astrophotography. Stars are the severest test of a lens, revealing optical aberrations that would go unnoticed in normal images, or even in photos of test charts. Many older zooms just didn’t cut it for discerning astrophotographers, myself included. 

The new generation of premium zooms for mirrorless cameras, from Canon, Nikon and Sony, are dispelling the old wisdom that primes are better than zooms. The new zooms’ optical performance is proving to be as good, if not better than the older generation of prime lenses for DSLR cameras, models often designed decades ago. 

The shorter lens-to-sensor “flange distance” offered by mirrorless cameras, along with new types of glass, provide lens designers more freedom to correct aberrations, particularly in wide-angle lenses. 

While usually slower than top-of-the-line primes, the advantage of zoom lenses is their versatility for framing and composing subjects, great for nightscapes and constellation shots. It’s nice to have the flexibility of a zoom without sacrificing the optical quality and speed so important for astrophotography. Can we have it all? The new zooms come close to delivering.

The “holy trinity” of Canon zooms tested were purchased in 2021 and 2022. From L to R they are: RF15-35mm, RF28-70mm, and RF70-200mm

A good thing, because with Canon we have little choice! For top-quality glass in wide-angle focal lengths at least, zooms are the only choice for their mirrorless R cameras. As of this writing in late 2022, Canon has yet to release any premium primes for their RF mount shorter than 50mm. Rumours are a 12mm, 24mm, 28mm, and 35mm are coming! But when? 

The three zooms I tested are all “L” lenses, designating them as premium-performance models. I have not tested any of Canon’s “economy” line of RF lenses, such as their 24mm and 35mm Macro STM primes. Tests I’ve seen suggest they don’t offer the sharpness I desire for most astrophotography. 

Contributing to the lack of choice, top-quality third-party lenses from the likes of Sigma (such as their new 20mm and 24mm Art lenses made for mirrorless cameras) have yet to appear in Canon RF mount versions. Will they ever? In moves that evoked much disdain, Samyang and Viltrox were both ordered by Canon to cease production of their RF auto-focus lenses. 

For their mirrorless R cameras, Canon has not authorized any third-party lens makers, forcing you to buy costly Canon L glass, or settle for their lower-grade STM lenses, or opt for reverse-engineered manual-focus lenses from makers such as TTArtisan and Laowa/Venus Optics. While they are good, they are not up to the optical standards of Canon’s L-series glass.

I know, as I own several RF-mount TTArtisan wide-angle lenses and the Laowa 15mm f/2 lens. You can find my tests of those lenses at AstroGearToday.com. Look under Reviews: Astrophotography Gear. 

RF lenses will fit only on Canon R-series mirrorless cameras. This shows the RF15-35mm on the Canon R5 used for the lens testing. 

The trio of RF lenses tested here work on all Canon EOS R-series cameras, including their R7 and R10 cropped-frame cameras. However, they will not work on any Canon DSLRs. 

Two of the lenses, the RF15-35mm F/2.8 and RF70-200mm F/4, are designs updated from older Canon DSLR lenses with similar specs. The RF28-70mm F/2 does not have an equivalent focal length range and speed in Canon’s DSLR lens line-up. Indeed, nobody else makes a lens this fast covering the “normal” zoom range. 

Together, the three lenses cover focal lengths from 15mm to 200mm, with some overlap. A trio of zooms like this — a wide-angle, normal, and telephoto — is often called a “holy trinity” set, a popular combination all camera manufacturers offer to cover the majority of applications. 

However, my interest was strictly for astrophotography, with stars the test subjects.  

NOTE: CLICK or TAP on a test image to download a full-resolution image for closer inspection. The images, while low-compression JPGs, are large and numerous, and so will take time to fully load and display. Patience! 

All images are © 2022 by Alan Dyer/AmazingSky.com. Use without permission is prohibited.

METHODOLOGY

I tested the trio of lenses on same-night exposures of a starry but moonlit sky, using the 45-megapixel Canon R5 camera mounted on a motorized star tracker to follow the rotating sky. With one exception noted, any distortion of stars from perfect pinpoints is due to lens aberrations, not star trailing. The brighter moonlit sky helped reveal non-uniform illumination from lens vignetting. 

I shot each lens wide-open at its maximum aperture, as well as one stop down from maximum, to see how aberrations and vignetting improved. 

I did not test auto-focus performance, nor image stabilization (only the RF28-70mm lacks internal IS), nor other lens traits unimportant for astro work such as bokeh or close focus image quality.

I also compared the RF15-35mm on same-night dark-sky tests against a trio of prime lenses long in my stable: the Rokinon 14mm SP, and Canon’s older L-series 24mm and 35mm primes, all made for DSLRs.

The lenses each come with lens hoods that use a click-on mechanism much easier to twist on and off than with the older design used on Canon EF lenses.

TL;DR SUMMARY

  • Each of the Canon “holy trinity” of zoom performs superbly, though not without some residual lens aberrations such as corner astigmatism and, in the RF28-70mm, slight chromatic aberration at f/2. 
  • However, what flaws they show are well below the level of many older prime lenses made for DSLR cameras. 
  • The RF lenses’ major optical flaw is vignetting, which can be quite severe at some focal lengths, such as in the RF70-200mm at 200mm. But this flaw can be corrected in processing. 
  • These are lenses that can replace fixed-focal length primes, though at considerable cost, in part justifiable in that they negate the need for a suite of many prime lenses.
  • The performance of these and other new lenses made for mirrorless cameras from all brands is one good reason to switch from DSLR to mirrorless cameras. 

Lens Specs and Applications 

Canon RF15-35mm F/2.8 L IS USM

The RF15-35mm is a fine nightscape lens. It extends slightly when zooming with the lens physically longest at its shortest 15mm focal length. 

The Canon RF15-35mm F/2.8 L is made primarily for urban photography and landscapes by day. My main application is using it to take landscapes by night, and auroras, where its relatively fast f/2.8 speed helps keeps exposure times short and ISO speeds reasonably low. However, the RF15-35mm can certainly be used for tracked wide-angle Milky Way and constellation portraits. 

The lens weighs a moderate 885 grams (31 ounces or 1.9 pounds) with lens hood and end caps, and accepts 82mm filters, larger than the 72mm or 77mm filter threads of most astrophoto-friendly lenses. Square 100mm filters will work well on the lens, even at the 15mm focal length. There are choices, such as from KASE, for light pollution reduction and star diffusion filters in this size and format. I have reviews of these filters at AstroGearToday.com, both here for light pollution filters and here for starglow filters. 

Canon offers a lower-cost alternative in this range, their RF14-35mm. But it is f/4, a little slow for nightscape, aurora, and Milky Way photography. I have not tested one. 

Canon RF28-70mm F/2 L USM

The RF28-70mm works great for tracked starfields and constellations. It extends when zooming, with it longest at its 70mm focal length. 

The big Canon RF28-70mm F/2 is aimed at wedding and portrait photographers, though the lens is suitable for landscape work. While I do use it for nightscapes, my primary use is for tracked Milky Way and constellation images, where its range of fields of view nicely frames most constellations, from big to small. 

I justified its high cost by deciding it replaces (more or less!) prime lenses in the common 24mm, 35mm, 50mm, and 85mm focal lengths. Its f/2 speed does bring it into fast prime lens territory. It’s handy to have just one lens to cover the range.

Canon offers a lower-cost alternative here, too, their RF24-70mm. But it is f/2.8. While this is certainly excellent speed, I like having the option of shooting at f/2. An example is when using narrowband nebula filters such as red hydrogen-alpha filters, where shooting at f/2 keeps exposures shorter and/or ISOs lower when using such dense filters. I use this lens with an Astronomik 12-nanometre H-α clip-in filter. An example is in one of the galleries below. 

While a clip-in filter shifts the infinity focus point inward (to as close as the 2-metre mark with the RF28-70mm at 28mm, and to 6 metres at 70mm), I did not find that shift adversely affected the lens’s optical performance. That’s not true of all lenses.

Make no mistake, the RF28-70mm is one hefty lens, weighing 1530 grams (54 ounces or 3.4 pounds). Its front-heavy mass demands a solid tripod head. Its large front lens accepts big 95mm filters, a rare size with few options available. I found one broadband light pollution filter in this size, from URTH. Otherwise, you need to use in-body clip-in filters. Astronomik makes a selection for Canon EOS R cameras.

Canon RF70-200mm F/4 L IS USM

The RF70-200mm works well for closeups of landscape scenes such as moonrises. It extends the most of all the lenses when zooming to its longest focal length. 

The Canon RF70-200mm F/4 is another portrait or landscape lens. I use it primarily for bright twilight planet conjunctions and moonrise scenes, where its slower f/4 speed is not a detriment. However, as my tests show, it can be used for tracked deep-sky images, where it is still faster than most short focal length telescopes. 

The RF70-200mm lens weighs 810 grams (28 ounces, or 1.75 pounds) with lens hood and caps, so is light for a 70-to-200mm zoom. It is also compact. At just 140mm long when set to 70mm, it is actually the shortest lens of the trio. However, the barrel extends to 195mm long when zoomed out to 200mm focal length. 

Canon offers the more costly and, at 1200 grams, heavier RF70-200mm F/2.8 lens which might be a better choice for deep-sky imaging where the extra stop of speed can be useful. But in this case, I chose the slower, more affordable – though still not cheap – f/4 version. It accepts common 77mm filters, as does the f/2.8 version. 

Centre Sharpness

Canon RF15-35mm F/2.8 L IS USM

This compares 400% blow-ups of the frame centres at the two extreme focal lengths and at two apertures: wide open at f/2.8 and stopped down to f/4. 

Like the other two zoom lenses tested, the RF15-35mm is very sharp on axis. Even wide open, there’s no evidence of softness and star bloat from spherical aberration, the bane of cheaper lenses. 

Coloured haloes from longitudinal chromatic aberration are absent, except at 28mm and 35mm (shown here) when wide open at f/2.8, where bright stars show a little bit of blue haloing. At f/4, this minor level of aberration disappears.

Canon RF28-70mm F/2 L USM

This compares 400% blow-ups of the frame centres at the two extreme focal lengths and at two apertures: wide open at f/2 and stopped down to f/2.8.

The big RF28-70mm is also very sharp on-axis but is prone to more chromatic aberration at f/2, showing slight magenta haloes on bright stars at the shorter focal lengths and pale cyan haloes at 70mm in my test shots. Such false colour haloes can be very sensitive to precise focus, though with refractive optics the point of least colour is often not the point of sharpest focus. 

At f/2, stars are a little softer at 70mm than at 28mm. Stopping down to f/2.8 eliminates this slight softness and most of the longitudinal chromatic aberration. 

Canon RF70-200mm F/4 L IS USM

This compares 400% blow-ups of the frame centres at the two extreme focal lengths and at two apertures: wide open at f/4 and stopped down to f/5.6.

Unlike prime telephotos I’ve used, the RF70-200mm shows negligible chromatic aberration on-axis at all focal lengths, even at f/4. Stars are a little softer at the longest focal length at f/4, perhaps from slight spherical aberration, though my 200mm test shots are also affected by a little mistracking, trailing the stars slightly. 

Stopping down to f/5.6 sharpens stars just that much more at 200mm. 

Corner Aberrations

The corners are where we typically separate great lenses from the merely good. And it is where zoom lenses have traditionally performed badly. For example, my original Canon EF16-35mm f/2.8 lens was so bad off-axis I found it mostly unusable for astro work. Not so the new RF15-35mm, which is the RF replacement for Canon’s older EF16-35mm.

To be clear – in these test shots you might think the level of aberrations are surprising for premium lenses. But keep in mind, to show them at all I am having to pixel-peep by enlarging all the test images by 400 percent, cropping down to just the extreme corners. 

Check the examples in the Compared to DSLR Lenses section and in the Finished Images Galleries for another look at lens performance in broader context. 

Canon RF15-35mm F/2.8 L IS USM

This compares 400% blow-ups of the extreme corners at five focal lengths with the RF15-35mm wide open at f/2.8

Surprisingly, this RF’s best performance off-axis is actually at its shortest focal length. At 15mm it exhibits only some slight tangential astigmatism, elongating stars away from the frame centre. At 24mm aberrations appear slightly worse than at the other focal lengths, showing some flaring from sagittal astigmatism and perhaps coma as well, aberrations seen to a lesser degree at 28mm and 35mm, making stars look like little three-pointed triangles. 

This compares 400% blow-ups of the extreme corners at five focal lengths with the RF15-35mm stopped down one stop to f/4.

The aberrations reduce when stopped down to f/4, but are still present, especially at 24mm, this lens’s weakest focal length, though only just. 

While the RF15-35mm isn’t perfect, it outperforms other prime lenses I have, and that I suspect most users will own or have used in the past with DSLRs. Only new wide-angle premium primes for the RF mount, if and when we see them, will provide better performance. 

Canon RF28-70mm F/2 L USM

This compare 400% blow-ups of the extreme corners at four focal lengths with the RF28-70mm wide open at f/2.

The RF28-70mm’s fast f/2 speed, unusual for any zoom lens, was surely a challenge to design for. Off-axis when wide open at f/2 it does show astigmatism at the extreme corners at all focal lengths, but the least at 50mm, and the worst at 28mm where a little lateral chromatic aberration is also visible, adding slight colour fringing. 

This compare 400% blow-ups of the extreme corners at four focal lengths with the RF28-70mm stopped down one stop to f/2.8.

Sharpness off-axis improves markedly when stopped down one stop to f/2.8, where at 50mm stars are now nearly perfect to the corners. Indeed, performance is so good at 50mm, I think there would be little need to buy the Canon RF50mm prime, unless its f/1.2 speed is deemed essential. 

With the RF28-70mm at f/2.8, stars still show some residual astigmatism at 28mm and 35mm, but only at the extreme corners. 

Canon RF70-200mm F/4 L IS USM

This compare 400% blow-ups of the extreme corners at four focal lengths with the RF70-200mm wide open at f/4.

The RF70-200mm telephoto zoom shows some astigmatism and coma at the corners when wide open at f/4, with it worse at the shorter focal lengths. While lens corrections have been applied here, the 200mm image still shows a darker corner from the vignetting described below. 

This compare 400% blow-ups of the extreme corners at four focal lengths with the RF70-200mm stopped down one stop to f/5.6.

Stopping down to f/5.6 eliminates most of the off-axis aberrations at 135mm and 200mm focal lengths but some remain at 70mm and to a lesser degree at 100mm. 

This is a lens that can be used at f/4 even for the demands of deep-sky imaging, though perfectionists will want to stop it down. At f/5.6 it is similar in speed to many astrographic refractors, though most of those start at about 250mm focal length. 

Frame Vignetting

In the previous test images, I applied lens corrections (but no other adjustments) to each of the raw files in Adobe Camera Raw, using the settings ACR automatically selects from its lens database. These corrections brightened the corners.

In this next set I show the lenses’ weakest point, their high level of vignetting. This light falloff darkens the corners by a surprising amount. In the new generation of lenses for mirrorless cameras, it seems lens designers are choosing to sacrifice uniform frame illumination in order to maximize aberration corrections. The latter can’t be corrected entirely, if at all, by software. 

However, corrections applied either in-camera or at the computer can brighten corners, “flattening” the field. I show that improvement in the section that follows this one.

Canon RF15-35mm F/2.8 L IS USM

This compares the level of vignetting present in the RF15-35mm without the benefit of lens corrections, showing the difference at five focal lengths. 

In the wide-angle zoom, vignetting darkens just the corners at 15mm, but widens to affect progressively more of the frame at the longer focal lengths. The examples show the entire right side of the frame. I show the effect just at f/2.8. 

Though I don’t show examples with the two wider zooms, with all lenses vignetting decreases dramatically when each lens is stopped down by even one stop. The fields become much more evenly illuminated, though some darkening at the very corners remains one stop down.

Canon RF28-70mm F/2 L USM

This compares the level of vignetting present in the RF28-70mm without the benefit of lens corrections, showing the difference at four focal lengths.

In this “normal” zoom, vignetting performance is similar at all focal lengths, though it affects a bit more of the field at 70mm than at 28mm. Again, while I’m not presenting an example, vignetting decreases a lot when this lens is stopped down to f/2.8. While the extra stop of speed is certainly nice to have at times, I usually shoot the RF28-70mm at f/2.8.

Canon RF70-200mm F/4 L IS USM

This compares the level of vignetting present in the RF70-200mm without the benefit of lens corrections, showing the difference at four focal lengths.

In this telephoto zoom, vignetting is fairly mild at the shorter focal lengths but becomes severe at 200mm, affecting much of the field. It is far worse than I see with my older Canon EF200mm f/2.8 prime, a lens that is not as sharp at f/4 as the RF zoom. 

The faster RF70-200mm f/2.8 lens, which I had the chance to test one night last year, showed as much, if not more, vignetting than the f/4 version. See my test here at AstroGearToday.com. I thought the f/4 version would be better for vignetting, but it is not.

This shows how much the RF-70-200mm’s vignetting improves when it is stopped down.

In this case, as the vignetting is so prominent at 200mm, I show above how much it improves when stopped down to f/5.6, in a comparison with the lens at f/4, both with no lens corrections applied in processing. The major improvement comes from the smaller aperture alone. For twilight scenes, I’d suggest stopping this lens down to better ensure a uniform sky background. 

LENS Corrections

In this next set I show how well applying lens corrections improves the vignetting at the focal lengths where each of the lenses is at its worse, and with each at its widest aperture. 

I show this with Adobe Camera Raw but Lightroom would provide identical results. I did not test lens corrections with other programs such as CaptureOne, DxO PhotoLab, or ON1 Photo Raw, which all have automatic lens corrections as well.

Canon RF15-35mm F/2.8 L IS USM

This compare the RF15-35mm lens at f/2.8 and 35mm with and without lens corrections applied, to show how much they improve the vignetting. 

Applying lens corrections in Adobe Camera Raw certainly brightened the corners and edges, though still left some darkening at the very corners that can be corrected by hand in the Manual tab. 

Canon RF28-70mm F/2 L USM

This compare the RF28-70mm lens at f/2 and 70mm with and without lens corrections applied, to show how much they improve the vignetting.

ACR’s lens corrections helped but did not completely eliminate the vignetting here. Corner darkening remained. Manually increasing the vignetting slider can provide that extra level of correction needed. 

Canon RF70-200mm F/4 L IS USM

This compare the RF70-200mm lens at f/4 and 200mm with and without lens corrections applied, to show how much they improve the vignetting.

The high level of vignetting with this lens at 200mm largely disappeared with lens corrections, though not entirely. For deep-sky imaging, users might prefer to shoot and apply flat-field frames. I prefer to apply automatic and manual corrections to the raw files, to stay within a raw workflow as much as possible. 

Same Focal Length Comparisons

With the trio of lenses offering some of the same focal lengths, here I show how they compare at three of those shared focal lengths. I zoom into the upper right corners here, as with the Corner Aberrations comparisons above. 

RF15-35mm vs. RF28-70mm at 28mm

This compares the RF15-35mm at 28mm to the RF28-70mm also at 28mm and with both at f/2.8.

With both lenses at 28mm and at the same f/2.8 aperture (though the RF28-70mm is now stopped down one stop), it’s a toss up. Both show corner aberrations, though of a different mix, distorting stars a little differently. The RF28-70mm shows some lateral chromatic aberration, but the RF15-35mm shows a bit more flaring from astigmatism. 

RF15-35mm vs. RF28-70mm at 35mm

This compares the RF15-35mm at 35mm to the RF28-70mm also at 35mm and with both at f/2.8.

The story is similar with each lens at 35mm. Stars seem a bit sharper in the RF15-35mm though are elongated more by astigmatism at the very corners. Lens corrections have been applied here and with the other two-lens comparison pairs. 

RF28-70mm vs. RF70-200mm at 70mm

This compares the RF28-70mm at 70mm and f/2.8 to the RF70-200mm also at 70mm but wide open at f/4.

Here I show the RF28-70mm at f/2.8 and the RF70-200mm wide open at f/4, with both set to 70mm focal length. The telephoto lens shows a little more softening and star bloating from corner aberrations, though both perform well.

Compared to DSLR Lenses

Here I try to demonstrate just how much better at least one of the zooms on test here is compared to older prime lenses made for DSLRs. The Canon lenses are labeled EF, for Canon’s EF lens mount used for decades on their DSLRs and EOS film cameras. Both are premium L lenses. 

I shot this set on a different night than the previous examples, with some light cloud present which added various amounts of glows around stars. But the test shots still show corner sharpness and aberrations well, in this case of the upper left corners of all frames. 

Canon RF15-35mm at 35mm vs. Canon EF35mm L

This compares the RF15-35mm zoom at 35mm to the older EF35mm L prime lens. Some light cloud added the glows at right.

The Canon EF35mm is the original Mark I version, which Canon replaced a few years ago with an improved Mark II model. So I’m sure if you were to buy an EF35mm lens now (or if that’s the model you own) it will perform better than what I show here. 

Both lenses are at f/2.8, wide open for the RF lens, but stopped down two stops for the f/1.4 EF lens. 

The zoom lens is much sharper to the corners, with far less astigmatism and none of the lateral chromatic aberration and field curvature (softening stars at the very corner) of the old EF35mm prime. I thought the EF35mm was a superb lens, and used it a lot over the last 15 years for Milky Way panoramas. I would not use it now! 

Canon RF15-35mm at 24mm vs. Canon EF24mm L

This compares the RF15-35mm zoom at 24mm to the older EF24mm L prime lens. Some light cloud added the glows at right.

Bought in the early years of DSLRs, the EF24mm tested here is also an original Mark I model, since replaced by an improved Mark II 24mm. The old 24mm is good, but shows more astigmatism than the RF lens, and some field curvature and purple chromatic aberration not present at all in the RF lens. 

And this is comparing it to the RF lens at its weakest focal length, 24mm. It still handily outperforms the old EF24mm prime. 

Canon RF15-35mm at 15mm vs. Rokinon 14mm SP

This compares the RF15-35mm at 15mm to the Rokinon 14mm SP prime lens.

Canon once made an EF14mm f/2.8 L prime, but I’ve never used it. For a lens in this focal length, one popular with nightscape photographers, I’ve used the ubiquitous Rokinon/Samyang 14mm f/2.8 manual lens. While a bargain at about $300, I always found it soft and aberrated at the corners. See my test of 14mm ultra-wides here. 

A few years ago I upgraded to the Rokinon 14mm f/2.4 lens in their premium SP series (about $800 for the EF-mount version). While a manual lens, it does have electrical contacts to communicate lens metadata to the camera. Like all EF-mount lenses from any brand, it can be adapted to Canon R cameras using Canon’s $100 EF-EOS R lens adapter.

Older DSLR lenses like the Rokinon SP can be adapted to all Canon R cameras with the Canon lens adapter ring which transmits lens data to the camera. 

The Rokinon SP is the only prime I found that beat the RF zoom. It provided sharper images to the corners than the RF15-35mm at 15mm. The Rokinon also offers the slightly faster maximum aperture of f/2.4 (which Canon cameras register as f/2.5). Vignetting is severe, but like the RF lenses can be corrected – Camera Raw has this lens in its database. What is not so easy to correct is some slight colour shift at the corners.

Another disadvantage, as with many other 14mm lenses, is that the SP lens cannot accept front-mounted filters. The RF15-35mm can. 

Nevertheless, until Canon comes out with a 12mm to 14mm RF prime, or allows Sigma to, an adapted Rokinon 14mm SP is a good affordable alternative to the RF15-35mm.

The RF15-35mm (left) takes 82mm filters, the RF28-70mm (centre) requires 95mm filters, but the RF70-200mm (right) can accept common 77mm filters. 

Mechanical Points

  • All the RF lens bodies are built of weight-saving engineered plastic incorporating thorough weather sealing. There is nothing cheap about their fit, finish or handling. Each lens has textured grip rings for the zoom, focus and a control ring that can be programmed to adjust either aperture, ISO, exposure compensation or other settings of your choosing. 
  • As with all modern auto-focus lenses, the manual focus ring on each lens does not mechanically move glass. It controls a motor that in turn focuses the lens, so-called “focus-by-wire.” However, I found that focus could be dialled in accurately. But if the camera is turned off, then on again, the lens will not return to its previous focus position. You have to refocus to infinity each time the camera is powered up, a nuisance. 
  • Unlike some Nikon, Sony, Samyang, and Sigma lenses, none of the Canon lenses have a focus lock button, or any way of presetting an infinity focus point, or simply having the lens remember where it was last set. I would hope Canon could address that deficiency in a firmware update. 
  • With all the zooms, I did not find any issue with “zoom creep.” The telescoping barrels  remained in place during long exposures and did not slowly retract when aimed up. While the RF28-70mm and RF70-200mm each have a zoom lock switch, it locks the lens only at its shortest focal length. 
  • Each lens is parfocal within its zoom range. Focus at one zoom position, and it will be in focus for all the focal lengths. I usually focus at the longest focal length where it is easiest to judge focus by eye, then zoom out to frame the scene. 

FINISHED IMAGES GALLERIES

Here I present a selection of final, processed images (four for each lens), so you can better see how each performs on real-world celestial subjects. To speed download, the images are downsized to 2048 pixels wide.

As per my comments at top, the RF15-35mm is my primary nightscape lens, the RF28-70mm my lens for wide-field constellation and Milky Way shots, while the RF70-200mm is for conjunctions and Moon scenes. It would also be good for eclipses.

Image Gallery with Canon RF15-35mm F/2.8 L IS USM

Image Gallery with Canon RF28-70mm F/2 L USM

Orion in H-Alpha Light with Narrowband Filter

Image Gallery with Canon RF70-200mm F/4 L IS USM

Click on the images to bring them up full screen with caption information.

CONCLUSIONs and recommendations

If you are a Canon user switching from your aging but faithful DSLR to one of their mirrorless R cameras, each of these lenses will perform superbly for astrophotography. At a price! Each is costly. But the cost of older EF lenses has also increased in recent months. 

The other native RF L-series lenses in this focal length range, Canon’s RF50mm and RF85mm f/1.2 primes, are stunning … but also expensive. As I’m sure any coming RF wide-angle L primes will be, if and when they ever appear! 

This shows the relative difference in size and height of the lens trio, with all collapsed to their minimum size. 

The cheaper alternative – not the least because you might already own them! – is using adapted EF-mount lenses made for DSLRs, either from Canon or other brands. But in many cases, as I’ve shown, the new RF glass is sharper, especially when on a high-resolution camera such as the Canon R5 I used for all the testing. 

And there’s the harsh reality that Canon is discontinuing many EF lenses. You can now buy some only used. For example, the EF135mm f/2 L and EF200mm f/2.8 L are both gone. 

Until Canon licenses other companies to issue approved lenses for their RF mount – if that happens at all – our choices for native RF lenses are limited. However, the quality of Canon’s L lenses is superb. I now use these zooms almost exclusively, and financed most of their considerable cost by selling off a ream of older cameras and lenses. 

If there’s one lens to buy for most astrophotography, it might be the big RF28-70mm F/2, a zoom lens that comes close to offering it all: flexibility, optical quality and speed. The RF24-70mm F/2.8 is a more affordable choice, though I have not tested one. 

If nightscapes are the priority, the RF15-35mm F/2.8 would see a lot of use, as perhaps the only lens you’d need. 

Of the trio, the RF70-200mm was the lowest priority on my wish list. But it has proven to be very useful for framing horizon scenes. 

The superb optics of these and other new lenses made for mirrorless cameras is one good reason to upgrade from a DSLR to a mirrorless camera, in whatever brand you prefer.

— Alan, September 21, 2022 / © 2022 Alan Dyer / AmazingSky.com  

All images are © 2022 by Alan Dyer/AmazingSky.com. Use without permission is prohibited.

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How to Photograph Comet NEOWISE


Comet over Hoodoos at Dinosaur Park in Twilight (July 14, 2020)A bright comet is a once-a-decade opportunity to capture some unique nightscapes. Here are my suggested tips and FAQs for getting your souvenir shot. 

My guide to capturing Comet NEOWISE assumes you’ve done little, if any, nightscape photography up to now. Even for those who have some experience shooting landscape scenes by night, the comet does pose new challenges — for one, it moves from night to night and requires good planning to get it over a scenic landmark. 

So here are my tips and techniques, in answers to the most frequently asked questions I get and that I see on social media posts.

Comet over Hoodoos at Dinosaur Park (July 14, 2020)
Comet NEOWISE (C/2020 F3) over the eroded hoodoo formations at Dinosaur Provincial Park, Alberta, July 14-15, 2020. A faint aurora is at right. The foreground is lit by starlight only; there was no light painting employed here. This is a stack of 12 exposures for the ground to smooth noise, blended with a single untracked exposure of the sky, all at 20 seconds at f/2.8 and ISO 1600, all with the 35mm Canon lens and Canon 6D MkII camera.

How Long Will the Comet be Visible?

The comet is not going to suddenly whoosh away or disappear. It is in our northern hemisphere sky and fairly well placed for shooting and watching all summer.

But … it is now getting fainter each night so the best time to shoot it is now! Or as soon as clouds allow on your next clear night. 

As of this writing on July 18 it is still bright enough to be easily visible to the unaided eye from a dark site. How long this will be the case is unknown. 

But after July 23 and its closest approach to Earth the comet will be receding from us and that alone will cause it to dim. Later this summer it will require binoculars to see, but might still be a good photogenic target, but smaller and dimmer than it was in mid-July. 

Comet Path
This chart shows the position of Comet NEOWISE at nightly intervals through the rest of the summer. However, the rest of July are the prime nights left for catching the comet at its best. Click or tap on the image to download a full-res copy.

When is the Best Time to Shoot?

The comet has moved far enough west that it is now primarily an evening object. So look as soon as it gets dark each night. 

Until later in July it is still far enough north to be “circumpolar” for northern latitudes (above 50° N) and so visible all night and into the dawn. 

But eventually the comet will be setting into the northwest even as seen from northern latitudes and only visible in the evening sky. Indeed, by the end of July the comet will have moved far enough south that observers in the southern hemisphere anxious to see the comet will get their first looks. 

Comet NEOWISE over Red Deer River
Comet NEOWISE (C/2020 F3) over the Red Deer River from Orkney Viewpoint north of Drumheller, Alberta, on the morning of July 11, 2020. The sky is brightening with dawn twilight and a small display of noctilucent clouds is on the horizon at right. This is a two-segment vertical panorama with the 35mm Canon lens at f/2.8 and Canon 6D MkII at ISO 200 for 13 seconds each. Stitched with Adobe Camera Raw.

Where Do I Look? 

In July look northwest below the Big Dipper. By August the comet is low in the west below the bright star Arcturus. By then it will be moving much less from night to night. The chart above shows the comet at nightly intervals; you can see how its nightly motion slows as it recedes from us and from the Sun. 

Selfie Observing Comet NEOWISE (July 15, 2020)
A selfie observing Comet NEOWISE (C/2020 F3) with binoculars on the dark moonless night of July 14/15, 2020 from Dinosaur Provincial Park, Alberta. A faint aurora colours the sky green and magenta. The faint blue ion tail of the comet is visible in addition to its brighter dust tail. The ground is illuminated by starlight and aurora light only. This is a blend of 6 exposures stacked for the ground (except me) to smooth noise, and one exposure for the sky and me, all 13 seconds at f/2.5 with the 35mm lens and Canon 6D MkII at ISO 6400. Topaz DeNoise AI applied.

What Exposures Do I Use?

There is no single best setting. It depends on …

— How bright the sky is from your location (urban vs a rural site).

— Whether the Moon is up — it will be after July 23 or so when the Moon returns to the western sky as a waxing crescent.

— The phase of the Moon — in late July it will be waxing to Full on August 3 when the sky will be very bright and the comet faint enough it might lost in the bright sky.

However, here are guidelines:

— ISO 400 to 1600

— Aperture f/2 to f/4

— Shutter speed of 4 to 30 seconds

Unless you are shooting in a very bright sky, your automatic exposure settings are likely not going to work.

As with almost all nightscape photography you will need to set your camera on Manual (M) and dial in those settings for ISO, Aperture and Shutter Speed manually. Just how is something you need to consult your camera’s instruction manual for, as some point-and-shoot snapshot cameras are simply not designed to be used manually.

Panorama of Comet NEOWISE Over Prince of Wales Hotel (July 14, 2
A once-in-a-lifetime scene — A panorama of the dawn sky at 4 am on July 14, 2020 from Waterton Lakes National Park, Alberta, Canada with Comet NEOWISE (C/2020 F3) over the iconic Prince of Wales Hotel. Noctilucent clouds glow below the comet in the dawn twilight. Venus is rising right of centre paired with Aldebaran and the Hyades star cluster, while the Pleiades cluster shine above. The waning quarter Moon shines above the Vimy Peak at far right. The Big Dipper is partly visible above the mountain at far left. Capella and the stars of Auriga are at centre. This is an 8-segment panorama with the 35mm Canon lens at f/2.5 for 15 seconds each at ISO 100 with the Canon 6D MkII and stitched with Adobe Camera Raw.

Exposure Considerations 

As a rule you want to …

— Keep the ISO as low as possible for the lowest noise. The higher the ISO the worse the noise. But … do raise the ISO high enough to get a well-exposed image. Better to shoot at ISO 3200 and expose well, than at ISO 800 and end up with a dark, underexposed image.

— Shoot at a wide aperture, such as f/2 or f/2.8. The wider the aperture (smaller the f-number) the shorter the exposure can be and/or lower the ISO can be. But … lens aberrations might spoil the sharpness of the image. 

— Keep exposures short enough that the stars won’t trail too much during the exposure due to Earth’s rotation. The “500 Rule” of thumb says exposures should be no longer than 500 / Focal length of your lens. 

So for a 50mm lens exposures should be no longer than 500/50 = 10s seconds. You’ll still see some trailing but not enough to spoil the image. And going a bit longer in exposure time can make it possible to use a slower and less noisy ISO speed or simply having a better exposed shot. 

Histogram
The histogram as shown in Adobe Camera Raw. Cameras also display the image’s histogram in the Live View preview and in playback of recorded images. Keep the histogram from slamming to the left.

— Avoid underexposing. If you can, call up the “histogram”— the graph of exposure values — on the resulting image in playback on your camera. The histogram should look fairly well distributed from left to right and not all bunched up at the left. 

Comet NEOWISE Over Dinosaur Park (July 15, 2020)
This is Comet NEOWISE (C/2020 F3) over the badlands and formations of Dinosaur Provincial Park, Alberta, on the night of July 14-15, 202. This is a blend of 6 exposures for the ground stacked to smooth noise, with a single exposure for the sky, with the 35mm Canon lens and Canon 6D MkII. The ground exposures are 1- and 2-minutes at ISO 1600 and f/2.8, while the single untracked sky exposure was 20 seconds at ISO 3200 and f/2.5.

My Nightscapes and Time-Lapses ebook shown above provides extensive instruction on the best camera settings for exposure and noise reduction.

Location Considerations

When and where you are will also affect your exposure combination. 

If you are at a site with lots of lights such as overlooking a city skyline, exposures will need to be shorter than at a dark site. 

And nights with a bright Moon will require shorter exposures than moonless nights.

Take test shots and see what looks good! Inspect the histogram. This isn’t like shooting with film when we had no idea if we got the shot until it was too late! 

What Lens Do I Use?

Comet over Canola Field (July 15, 2020)
With a 35mm lens. Comet NEOWISE (C/2020 F3) over a ripening canola field near home in southern Alberta, on the night of July 15-16, 2020. This is a blend of a stack of six 2-minute exposures at ISO 3200 and f/5.6 to smooth noise, provide depth of field, and bring out the colours of the canola, blended with a single short 15-second exposure of the sky at f/2.8 and ISO 1600, all with the 35mm lens and Canon 6D MkII camera.

Comet over Canola Field Close-Up (July 15, 2020)
With a 50mm lens. Comet NEOWISE (C/2020 F3) over a ripening canola field near home in southern Alberta, on the night of July 15-16, 2020. This is a blend of a stack of three 2-minute exposures at ISO 1600 and f/5 to smooth noise, provide depth of field, and bring out the colours of the canola, blended with a single short 15-second exposure of the sky at f/2.8 and ISO 3200, all with the 50mm Sigma lens and Canon 6D MkII camera.

Any lens can produce a fine shot. Choose the lens to frame the scene well. 

Using a longer lens (105mm to 200mm) does make the comet larger, but … might make it more difficult to also frame it above a landscape. A good choice is likely a 24mm to 85mm lens.

A fast lens is best, to keep exposure times below the 500 Rule threshold and ISO speeds lower. Slow f/5.6 kit zooms can be used but do pose challenges for getting well exposed and untrailed shots. 

Shooting with shorter focal lengths can help keep the aperture wider and faster. Long focal lengths aren’t needed, especially for images of the comet over a landscape. Avoid the temptation to use that monster 400mm or 600mm telephoto wildlife lens. Unless it is on a tracker (see below) it will produce a trailed mess. It is best to shoot with no more than a 135mm telephoto, the faster the better, IF you want a close-up.

Planetarium programs that I recommend below offer “field of view” indicators so you can preview how much of the horizon and sky your camera and lens combination will show. 

StarryNightFOV
StarryNight™ and other programs offer “Field of View” indicator frames that can show how the scene will frame with (in this example) lenses from 24mm to 135mm.

Can I Use My [insert camera here] Camera?

Yes. Whatever you have, try it. 

However, the best cameras for any nightscape photography are DSLRs and Mirrorless cameras, either full-frame or cropped frame. They have the lowest noise and are easiest to set manually. 

In my experience in teaching workshops I find that the insidious menus of automatic “point-and-shoot” pocket cameras make it very difficult to find the manual settings. And some have such noisy sensors they do not allow longer exposures and/or higher ISO speeds. But try their Night or Fireworks scene modes. 

It doesn’t hurt to try, but if you don’t get the shot, don’t fuss. Just enjoy the view with your eyes and binoculars. 

But … if you have an iPhone11 or recent Android phone (I have neither!) their “Night scene” modes are superb and use clever in-camera image stacking and processing routines to yield surprisingly good images. Give them a try — keep the camera steady and shoot. 

Comet NEOWISE with NLCs Above Prairie Lake (July 10-11, 2020)
This is Comet NEOWISE (C/2020 F3) over Deadhorse Lake near Hussar in southern Alberta, taken just after midnight on July 10-11, 2020 during its evening appearance. The comet shines just above low noctilucent clouds. This is a blend of nine exposures for the ground stacked to smooth noise and the water, with a single exposure for the sky, all 4 seconds with the 135mm Canon lens at f/2 and Canon 6D MkII at ISO 1600.

What No One Asks: How Do I Focus?

Everyone fusses about “the best” exposure. 

What no one thinks of is how they will focus at night. What ruins images is often not bad exposure (a lot of exposure sins can be fixed in processing) but poor focus (which cannot be fixed later).

On bright scenes it is possible your camera’s Autofocus system will “see” enough in the scene to work and focus the lens. Great.

On dark scenes it will not. You must manually focus. Do that using your camera’s “Live View” function (all DSLRs and Mirrorless cameras have it — but check your user manual as on DSLRs it might need to be activated in the menus if you have never used it). 

Canon 6D Live View Wide
The Live View screen of a Canon DSLR. Look in your manual for tips on how to boost the Live screen image brightness with the Exposure Simulation option.

Canon 6D Live View Zoom5x
Magnify the image 5x, 10x or more with the Zoom box centred on a star to focus the star to a pinpoint.

Aim at a bright star or distant light and magnify the image 5x or 10x (with the + button) to inspect the star or light. Put the lens on MF (not AF) and focus the lens manually to make the star as pinpoint as possible. Do not touch the lens afterwards. 

Practice on a cloudy night on distant lights.

All shooting must be done with a camera on a good tripod. As such, turn OFF any image stabilization (IS), whether it be on the lens or in the camera. IS can ruin shots taken on a tripod. 

What Few Ask: How Do I Plan a Shoot? 

Good photos rarely happen by accident. They require planning. That’s part of the challenge and satisfaction of getting the once-in-a-lifetime shot. 

To get the shot of the comet over some striking scene below, you have to figure out:

— First, where the comet will be in the sky, 

— Then, where you need to be to look toward that location. 

— And of course, you need to be where the sky will be clear!

Stellarium Web
The free web version of Stellarium shows the comet, as do the paid mobile apps.

  1. Planning Where the Comet Will Be 

Popular planning software such as PhotoPills and The Photographer’s Ephemeris can help immensely, but won’t have the comet itself included in their displays, just the position of the Sun, Moon and Milky Way.

For previewing the comet’s position in the sky, I use the planetarium programs Starry Night (desktop) or SkySafari (mobile app). Both include comet positions. 

The program Stellarium (stellarium.org) is free for desktop while the mobile Stellarium Plus apps (iOS and Android) have a small fee. There is also a free web-based version at https://stellarium-web.org  Be sure to allow it to access your location. 

Set the programs to the night in question to see where the comet will be in relation to the stars and patterns such as the Big Dipper. Note the comet’s altitude in degrees and azimuth (how far along the horizon it will be). For example, an azimuth of 320° puts it in the northwest (270° is due west; 0° or 360° is due north, 315° is directly northwest). 

Comet NEOWISE and NLCs over Prince of Wales Hotel (July 14, 2020
Comet NEOWISE (C/2020 F3) with a small display of noctilucent clouds over Emerald Bay and the iconic Prince of Wales Hotel at Waterton Lakes National Park, Alberta, at dawn on July 14, 2020. This is a blend of a stack of four exposures for the ground and water to smooth noise, blended with a single short exposure for the sky, all 20 seconds at f/2.5 and ISO 400. All with the 35mm Canon lens and Canon 6D MkII camera.

  1. Planning Where You Need To Be

I use The Photographer’s Ephemeris mobile app (https://www.photoephemeris.com) — there is a free web version available. Many like PhotoPills (https://www.photopills.com).

With either you can dial in the time and date and see lines pointing toward where the Sun would be, but below the horizon. Scrub through time to move that line to the same azimuth angle as where the comet will be and then see if the comet is sitting in the right direction. 

TPE
The screen from The Photographer’s Ephemeris app showing the planning map for the image above, with the faint yellow line indicating the line toward the comet’s azimuth.

Move your location to place the line toward the comet over what you want to include in the scene.

TPE 3D
The simulation of the real scene above, of the comet over the Prince of Wales Hotel, using TPE 3D app. The simulation matches the real scene very well!

I like The Photographer’s Ephemeris as it links to the companion app TPE3D that can show the stars over the actual topographic landscape. It won’t show the comet, but if you know where it is in the sky you can see if if will clear mountains, for example.

Astrospheric
The Astrospheric app prediction of skies for me for the night I prepared this blog. Not great! But clear skies could be found to to east with a fresh hours drive.

  1. Planning for the Weather 

All is for nought if the sky is cloudy. 

For planning astro shoots I like the app Astrospheric (https://www.astrospheric.com). It is free for mobile and there is a web-based version. It uses Environment Canada predictions of cloud cover for North America. Use it to plan where to be for clear skies first, then figure out the best scenic site that will be under those clear skies. 

For sites outside North America, try ClearOutside (https://clearoutside.com) 

Advanced Techniques 

Be happy to get a well-composed and exposed single shot. 

But … if you wish to try some more advanced techniques for later processing, here are suggestions.

Comet NEOWISE and Aurora Panorama (July 13, 2020)
A panorama of the sky just before midnight on July 13, 2020 from Waterton Lakes National Park, Alberta, Canada with Comet NEOWISE (C/2020 F3) over the front range of the Rocky Mountains and an arc of aurora across the north. This is a 6-segment panorama with the 35mm Canon lens at f/2.2 for 25 seconds each at ISO 800 with the Canon 6D MkII and stitched with Adobe Camera Raw.

1. Panoramas

On several nights I’ve found a panorama captures the scene better, including the comet in context with the wide horizon, sweep of the twilight arch or, as we’ve had in western Canada, some Northern Lights.

Take several identical exposures, moving the camera 10 to 15 degrees between images. Editing programs such as Lightroom, Adobe Camera Raw, ON1 Photo RAW and Affinity Photo have panorama stitching routines built in. 

My Nightscapes and Time-Lapses ebook shown above provides tutorials for shooting and processing nightscape panoramas. 

Comet NEOWISE over Red Deer River Panorama (July 11, 2020)
What a magical scene this was! This is Comet NEOWISE (C/2020 F3) over the sweep of the Red Deer River and Badlands from Orkney Viewpoint north of Drumheller, Alberta, on the morning of July 11, 2020. Light from the waning gibbous Moon provides the illumination, plus twilight. This nicely shows the arch of the twilight colours. This is a 6-segment panorama with the 50mm Sigma lens at f/2.8 and Canon 6D MkII at ISO 400 for 13 seconds each. Stitched with Adobe Camera Raw. Topaz DeNoise AI and Sharpen AI applied.

2. Exposure Blending 

If you have a situation where the sky is bright but the ground is dark, or vice versa, and one exposure cannot record both well, then shoot two exposures, each best suited to recording the sky and ground individually. 

For example, on moonless nights I’ve been shooting 2- to 5-minute long exposures for the ground and with the lens stopped down to f/5.6 or f/8 for better depth of field to be sure the foreground was in focus. 

For a video tutorial on how to do the layering and masking in programs such as Photoshop, see my How to Shoot Moonlit Nightscapes video at https://vimeo.com/theamazingsky/moonlighttutorial. 

Comet NEOWISE over Horseshoe Canyon (July 11, 2020)
This is Comet NEOWISE (C/2020 F3) over the Horseshoe Canyon formation near Drumheller, Alberta on the night of July 10-11, 2020, taken about 2 a.m. MDT with the comet just past lower culmination with it circumpolar at this time. Warm light from the rising waning gibbous Moon provides the illumination. This is a blend of six 1- and 2-minute exposures for the ground at ISO 800 and 400 stacked to smooth noise, with a single 30-second exposure at ISO 1600 for the sky, all with the 35mm Canon lens at f/2.8 and Canon 6D MkII.

3. Exposure Stacking 

To reduce noise, it is also possible to shoot multiple exposures to stack later in processing to smooth noise. This is most useful in scenes with dark foregrounds where noise is most obvious, and where I will stack 4 to 8 images. 

Just how to do this is beyond the scope of this blog. I also give step-by-step tutorials for the process in my Nightscapes and Time-Lapses ebook shown above. It be done in Photoshop, or in specialized programs such as StarryLandscapeStacker (for MacOS) or Sequator (Windows). 

But shoot the images now, and learn later how to use them. 

Comet NEOWISE Close-Up (July 15, 2020)
A close-up of Comet NEOWISE (C/2020 F3) on the night of July 14/15, 2020 with a 135mm telephoto lens. This is a stack of nine 1-minute exposures with the 135mm Canon lens wide-open at f/2 and Canon EOS Ra camera at ISO 800. The camera was on the iOptron SkyGuider Pro tracker tracking the stars not the comet. Stacked and aligned in Photoshop.

4. Tracking the Sky 

If it is close-ups of the comet you want, then you will need to use a 135mm to 300mm telephoto lens (especially later in the summer when the comet is farther away and smaller). 

But with such lenses any exposure over a few seconds will result in lots of trailing. 

iOptron SkyGuider Pro
The iOptron SkyGuider Pro and 135mm lens used to take the close-up shot of the comet above.

The solution is a tracking device such as the Sky-Watcher Star Adventurer or iOptron SkyGuider. These need to be set up so their rotation axis aims at the North Celestial Pole near Polaris. The camera can then follow the stars for the required exposures of up to a minute or more needed to record the comet and its tails well. 

Star Adventurer Polar Axis Angle
This is the Sky-Watcher Star Adventurer. All trackers have a polar axis that needs to be aligned to the Celestial Pole, near Polaris.

Just how to use a tracker is again beyond the scope of this blog. But if you have one, it will work very well for comet shots with telephoto lenses. However, trackers are not essential for wide-angle shots, especially once the Moon begins to light the sky.

But later in the summer when the comet is fainter and smaller, a tracked and stacked set of telephoto lens images will likely be the best way to capture the comet.

Clear skies and happy comet hunting!

— Alan, July 18, 2020 /Revised July 23 / AmazingSky.com 

 

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Testing the Venus Optics 15mm Lens


Laowa Test Title

I test out a fast and very wide lens designed specifically for Sony mirrorless cameras. 

In a previous test I presented results on how well the Sony a7III mirrorless camera performs for nightscape and deep-sky photography. It works very well indeed.

But what about lenses for the Sony? Here’s one ideal for astrophotography.

TL;DR Conclusions

Made for Sony e-mount cameras, the Venus Optics 15mm f/2 Laowa provides excellent on- and off-axis performance in a fast and compact lens ideal for nightscape, time-lapse, and wide-field tracked astrophotography with Sony mirrorless cameras. (UPDATE: Venus Optics has announced versions of this lens for Canon R and Nikon Z mount mirrorless cameras.)

I use it a lot and highly recommend it.

Size and Weight

While I often use the a7III with my Canon lenses by way of a Metabones adapter, the Sony really comes into its own when matched to a “native” lens made for the Sony e-mount. The selection of fast, wide lenses from Sony itself is limited, with the new Sony 24mm G-Master a popular favourite (I have yet to try it).

However, for much of my nightscape shooting, and certainly for auroras, I prefer lenses even wider than 24mm, and the faster the better.

Auroral Swirls over Båtsfjord, Norway Aurora over Båtsfjord, Norway. This is a single 0.8-second exposure at f/2 with the 15mm Venus Optics lens and Sony a7III at ISO 1600.

The Laowa 15mm f/2 from Venus Optics fills the bill very nicely, providing excellent speed in a compact lens. While wide, the Laowa is a rectilinear lens providing straight horizons even when aimed up, as shown above. This is not a fish-eye lens.

Laowa 15mm Front View with Filter Though a very wide lens, the 15mm Laowa accepts standard 72mm filters. The metal lens hood is removable. © 2019 Alan Dyer

The Venus Optics 15mm realizes the potential of mirrorless cameras and their short flange distance that allows the design of fast, wide lenses without massive bulk.

Sigma 14mm vs Laowa 15mm Sigma 14mm f/1.8 Art lens (for Nikon mount) vs. Venus Optics 15mm f/2 lens (for Sony mount). © 2019 Alan Dyer

While compact, at 600 grams the Laowa 15mm is quite hefty for its size due to its solid metal construction. Nevertheless, it is half the weight of the massive 1250-gram Sigma 14mm f/1.8 Art. The Laowa is not a plastic entry-level lens, nor is it cheap, at $850 from U.S. sources.

For me, the Sony-Laowa combination is my first choice for a lightweight travel camera for overseas aurora trips

Laowa 15mm Back View The lens mount showing no electrical contacts to transfer lens metadata to the camera. © 2019 Alan Dyer

However, this is a no-frills manual focus lens. Nor does it even transfer aperture data to the camera, which is a pity. There are no electrical connections between the lens and camera.

However, for nightscape work where all settings are adjusted manually, the Venus Optics 15mm works just fine. The key factor is how good are the optics. I’m happy to report that they are very good indeed.

Testing Under the Stars

To test the Venus Optics lens I shot “same night” images, all tracked, with the Sigma 14mm f/1.8 Art lens, at left, and the Rokinon 14mm SP (labeled as being f/2.4, at right). Both are much larger lenses, made for DSLRs, with bulbous front elements not able to accept filters. But they are both superb lenses. See my test report on these lenses published in 2018.

Sigma and Rokinon 14mm The Sigma 14mm f/1.8 Art lens (left) vs. the Rokinon SP 14mm f/2.4. © 2019 Alan Dyer

The next images show blow-ups of the same scene (the nightscape shown in full below, taken at Dinosaur Provincial Park, Alberta), and all taken on a tracker.

I used the Rokinon on the Sony a7III using the Metabones adapter which, unlike some brands of lens adapters, does not compromise the optical quality of the lens by shifting its focal position. But lacking a lens adapter for Nikon-to-Sony at the time of testing, I used the Nikon-mount Sigma lens on a Nikon D750, a DSLR camera with nearly identical sensor specs to the Sony.

Vignetting

Laowa 15mm @ f2 A tracked image with the Venus Optics Laowa 15mm at f/2. Click or tap on an image to download a full-resolution JPG for closer inspection.

Above is a tracked image (so the stars are not trailed, which would make it hard to tell aberrations from trails), taken wide open at f/2. No lens correction has been applied so the vignetting (the darkening of the frame corners) is as the lens provides.

As shown above, when used wide open at f/2 vignetting is significant, but not much more so than with competitive lenses with much larger lenses, as I compare below.

And the vignetting is correctable in processing. Adobe Camera Raw and Lightroom have this lens in their lens profile database. That’s not the case with current versions (as of April 2019) of other raw developers such as DxO PhotoLab, ON1 Photo RAW, and Raw Therapee where vignetting corrections have to be dialled in manually by eye.

Laowa 15mm @ f2.8 A tracked image with the Venus Optics Laowa 15mm stopped down 1 stop to f/2.8.

When stopped down to f/2.8 the Laowa “flattens” out a lot for vignetting and uniformity of frame illumination. Corner aberrations also improve but are still present. I show those in close-up detail below.

Lens Comparison - Vignetting 15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the left side of the image for vignetting (light fall-off), wide open and stopped down. ©2018 Alan Dyer

Above, I compare the vignetting of the three lenses, both wide open and when stopped down. Wide open, all the lenses, even the Sigma and Rokinon despite their large front elements, show quite a bit of drop off in illumination at the corners.

The Rokinon SP actually seems to be the worst of the trio, showing some residual vignetting even at f/2.8, while it is reduced significantly in the Laowa and Sigma lenses. Oddly, the Rokinon SP, even though it is labeled as f/2.4, seemed to open to f/2.2, at least as indicated by the aperture metadata.

On-Axis Performance

Lens Comparison - Centre 15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the centre of the image for sharpness, wide open and stopped down. Click or tap on an image to download a full-resolution JPG for closer inspection. © 2018 Alan Dyer

Above I show lens sharpness on-axis, both wide open and stopped down, to check for spherical and chromatic aberrations with the bright blue star Vega centered. The red box in the Navigator window at top right indicates what portion of the frame I am showing, at 200% magnification in Photoshop.

On-axis, the Venus Optics 15mm shows stars just as sharply as the premium Sigma and Rokinon lenses, with no sign of blurring spherical aberration nor coloured haloes from chromatic aberration.

Laowa 15mm Side with Focus Point This is where this lens reaches sharpest focus on stars, just shy of the Infinity mark. © 2019 Alan Dyer

Focusing is precise and easy to achieve with the Sony on Live View. My unit reaches sharpest focus on stars with the lens set just shy of the middle of the infinity symbol. This  is consistent and allows me to preset focus just by dialing the focus ring, handy for shooting auroras at -35° C, when I prefer to minimize fussing with camera settings, thank you very much!

Off-Axis Performance

Lens Comparison - Upper Left 15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the centre of the image for sharpness, wide open and stopped down. Click or tap on an image to download a full-resolution JPG for closer inspection. © 2018 Alan Dyer
Lens Comparison - Upper Right 15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the upper right corner of the image for aberrations, wide open and stopped down. © 2018 Alan Dyer

The Laowa and Sigma lenses show similar levels of off-axis coma and astigmatism, with the Laowa exhibiting slightly more lateral chromatic aberration than the Sigma. Both improve a lot when stopped down one stop, but aberrations are still present though to a lesser degree.

However, I find that the Laowa 15mm performs as well as the Sigma 14mm Art for star quality on- and off-axis. And that’s a high standard to match.

The Rokinon SP is the worst of the trio, showing significant elongation of off-axis star images (they look like lines aimed at the frame centre), likely due to astigmatism. With the 14mm SP, this aberration was still present at f/2.8, and was worse at the upper right corner than at the upper left corner, an indication to me that even the premium Rokinon SP lens exhibits slight lens de-centering, an issue users have often found with other Rokinon lenses.

Real-World Examples – The Milky Way

Sweep of the Autumn Milky Way This is a stack of 8 x 2-minute exposures with the Venus Optics Laowa 15mm lens at f/2 and Sony a7III at ISO 800, on the Sky-Watcher Star Adventurer tracker. A single exposure taken through the Kenko Softon A filter layered in with Lighten mode adds the star glows, though exaggerates the lens distortion on the bright stars.
Mars and the Milky Way over Writing-on-Stone This is a stack of 12 exposures for the ground, mean combined to smooth noise, and one exposure for the sky, all 30 seconds at f/2 with the Laowa 15mm lens on the Sony a7III camera at ISO 6400. These were the last frames in a 340-frame time-lapse sequence.

The fast speed of the Laowa 15mm is ideal for shooting tracked wide-field images of the Milky Way, and untracked camera-on-tripod nightscapes and time-lapses of the Milky Way.

Image aberrations are very acceptable at f/2, a speed that allows shutter speed and ISO to be kept lower for minimal star trailing and noise while ensuring a well-exposed frame.

Real World Examples – Auroras

Coloured Curtains over CNSC (Feb 9, 2019) Aurora over the Churchill Northern Studies Centre, Churchill, Manitoba. This is 6 seconds at f/2 with the 15mm Venus Optic lens and Sony a7III at ISO 3200.
Sky-Filling Aurora at Tibbitt Lake Aurora from near Yellowknife, NWT, September 8, 2018. This is 2.5-seconds at f/2 with the Venus Optics 15mm lens and Sony a7IIII at ISO 3200.
Aurora from at Sea Near Lofotens #1 The Northern Lights from at sea when leaving the Lofoten Islands, Norway heading toward the mainlaind, from Stamsund to Bodo, March 3, 2019. This was from the Hurtigruten ship the ms Trollfjord. This is a single 1-second exposure for at f/2 with the 15mm Venus Optics lens and Sony a7III at ISO 6400.

Where the Laowa 15mm really shines is for auroras. On my trips to chase the Northern Lights I often take nothing but the Sony-Laowa pair, to keep weight and size down.

Above is an example, taken from a moving ship off the coast of Norway. The fast f/2 speed (I wish it were even faster!) makes it possible to capture the Lights in only 1- or 2-second exposures, albeit at ISO 6400. But the fast shutter speed is needed for minimizing ship movement.

Video Links

The Sony also excels at real-time 4K video, able to shoot at ISO 12,800 to 51,200 without excessive noise.

Aurora Reflections from Alan Dyer on Vimeo.

The Sky is Dancing from Alan Dyer on Vimeo.

The Northern Lights At Sea from Alan Dyer on Vimeo.

Examples of my aurora videos shot with the Sony and Venus Optics 15mm lens are in previous blogs from Yellowknife, NWT in September 2018, from Churchill, Manitoba in February 2019, and from at sea in Norway in March 2019.

Click through to see the posts and the videos shot with the Venus Optics 15mm.

As an aid to video use, the aperture ring of the Venus Optics 15mm can be “de-clicked” at the flick of a switch, allowing users to smoothly adjust the iris during shooting, avoiding audible clicks and jumps in brightness. That’s a very nice feature indeed.

In all, I can recommend the Venus Optics Laowa 15mm lens as a great match to Sony mirrorless cameras, for nightscape still and video shooting. UPDATE: Versions for Canon R and Nikon Z mount mirrorless cameras will now be available.

— Alan, April 20, 2019 / © 2019 Alan Dyer / AmazingSky.com

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Photographing the Total Eclipse of the Moon


Lunar Eclipse CompositeOn the evening of January 20 for North America, the Full Moon passes through the umbral shadow of the Earth, creating a total eclipse of the Moon. 

No, this isn’t a “blood,” “super,” nor “wolf” Moon. All those terms are internet fabrications designed to bait clicks.

It is a   total   lunar  eclipse  — an event that doesn’t need sensational adjectives to hype, because they are always wonderful sights! And yes, the Full Moon does turn red.

As such, on January 20 the evening and midnight event provides many opportunities for great photos of a reddened Moon in the winter sky. 

Here’s my survey of tips and techniques for capturing the eclipsed Moon. 

First … What is a Lunar Eclipse?

As the animation below shows (courtesy NASA/Goddard Space Flight Center), an eclipse of the Moon occurs when the Full Moon (and they can happen only when the Moon is exactly full) travels through the shadow of the Earth. 

The Moon does so at least two times each year, though often not as a total eclipse, one where the entire disk of the Moon enters the central umbral shadow. Many lunar eclipses are of the imperceptible penumbral variety, or are only partial eclipses.

Total eclipses of the Moon can often be years apart. The last two were just last year, on January 31 and July 27, 2018. However, the next is not until May 26, 2021.

For a short explanation of the geometry of lunar eclipses see the NASA/Goddard video at https://svs.gsfc.nasa.gov/11516 

At any lunar eclipse we see an obvious darkening of the lunar disk only when the Moon begins to enter the umbra. That’s when the partial eclipse begins, and we see a dark bite appear on the left edge of the Moon. 

While it looks as if Earth’s shadow sweeps across the Moon, it is really the Moon moving into, then out of, our planet’s umbra that causes the eclipse. We are seeing the Moon’s revolution in its orbit around Earth. 

At this eclipse the partial phases last 67 minutes before and after totality. 

Telescope CU-Stages
This shows the length of the eclipse phases relative to the start of the partial eclipse as the Moon begins to enter the umbra at right. The Moon’s orbital motion takes it through the umbra from right to left (west to east) relative to the background stars. The visible eclipse ends 196 minutes (3 hours and 16 minutes) after it began. Click or tap on the charts to download a high-res version.

Once the Moon is completely immersed in the umbra, totality begins and lasts 62 minutes at this eclipse, a generous length. 

The Moon will appear darkest and reddest at mid-eclipse. During totality the lunar disk is illuminated only by red sunlight filtering through Earth’s atmosphere. It is the light of all the sunsets and sunrises going on around our planet. 

And yes, it is perfectly safe to look at the eclipsed Moon with whatever optics you wish. Binoculars often provide the best view. Do have a pair handy!

Total Lunar Eclipse (December 20/21, 2010)
Total eclipse of the Moon, December 20/21, 2010, taken from home with 130mm AP apo refractor at f/6 and Canon 7D at ISO 400 for 4 seconds, single exposure, shortly after totality began.

At this eclipse because the Moon passes across the north half of the umbra, the top edge of the Moon will always remain bright, as it did above in 2010, looking like a polar cap on the reddened Moon.

Near the bright edge of the umbra look for subtle green and blue tints the eye can see and that the camera can capture.

Where is the Eclipse?

As the chart below shows, all of the Americas can see the entire eclipse, with the Moon high in the evening or late-night sky. For the record, the Moon will be overhead at mid-eclipse at local midnight from Cuba!

LE2019Jan21T
All of the Americas can see this eclipse. The eclipse gets underway as the Moon sets at dawn over Europe. Diagram courtesy EclipseWise.com

For more details on times see www.EclipseWise.com and the event page at http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2019Jan21Tprime.html 

I live in Alberta, Canada, at a latitude of 50 degrees North. And so, the sky charts I provide here are for my area, where the Moon enters the umbral shadow at 8:35 p.m. MST with the Moon high in the east. By the end of totality at 10:44 p.m. MST the Moon shines high in the southeast. This sample chart is for mid-eclipse at my site.

Framing TL-Mid-Eclipse
The sky at mid-eclipse from my Alberta site. Created with the planetarium software Starry Night, from Simulation Curriculum.

I offer them as examples of the kinds of planning you can do to ensure great photos. I can’t provide charts good for all the continent because exactly where the Moon will be during totality, and the path it will take across your sky will vary with your location. 

In general, the farther east and south you live in North America the higher the Moon will appear. But from all sites in North America the Moon will always appear high and generally to the south. 

To plan your local shoot, I suggest using planetarium software such as the free Stellarium or Starry Night (the software I used to prepare the sky charts in this post), and photo planning apps such as The Photographer’s Ephemeris or PhotoPills. 

The latter two apps present the sightlines toward the Moon overlaid on a map of your location, to help you plan where to be to shoot the eclipsed Moon above a suitable foreground, if that’s your photographic goal. 

When is the Eclipse?

While where the Moon is in your sky depends on your site, the various eclipse events happen at the same time for everyone, with differences in hour due only to the time zone you are in. 

While all of North America can see the entirety of the partial and total phases of this eclipse (lasting 3 hours and 16 minutes from start to finish), the farther east you live the later the eclipse occurs, making for a long, late night for viewers on the east coast. 

Those in western North America can enjoy all of totality and be in bed at or before midnight.

Here are the times for the start and end of the partial and total phases. Because the penumbral phases produce an almost imperceptible darkening, I don’t list the times below for the start and end of the penumbral eclipse. 

Eclipse Times Table

PM times are on the evening of January 20.

AM times are after midnight on January 21.

Note that while some sources list this eclipse as occurring on January 21, that is true for Universal Time (Greenwich Time) and for sites in Europe where the eclipse occurs at dawn near moonset. 

For North America, if you go out on the evening of January 21 expecting to see the eclipse you’ll be a day late and disappointed! 

Picking a Photo Technique

Lunar eclipses lend themselves to a wide range of techniques, from a simple camera on a tripod, to a telescope on a tracking mount following the sky. 

If this is your first lunar eclipse I suggest keeping it simple! Select just one technique, to focus your attention on only one camera on a cold and late winter night. 

Lunar Eclipse Closeup with Stars
The total eclipse of the Moon of September 27, 2015, through a telescope, at mid-totality with the Moon at its darkest and deepest into the umbral shadow, in a long exposure to bring out the stars surrounding the dark red moon. This is a single exposure taken through a 92mm refractor at f/5.5 for 500mm focal length using the Canon 60Da at ISO 400 for 8 seconds. The telescope was on a SkyWatcher HEQ5 equatorial mount tracking at the lunar rate.

Then during the hour of totality take the time to enjoy the view through binoculars and with the unaided eye. No photo quite captures the glowing quality of an eclipsed Moon. But here’s how to try it.

Option 1: Simple — Camera-on-Tripod

The easiest method is to take single shots using a very wide-angle lens (assuming you also want to include the landscape below) with the camera on a fixed tripod. No fancy sky trackers are needed here. 

During totality, with the Moon now dimmed and in a dark sky, use a good DSLR or mirrorless camera in Manual (M) mode (not an automatic exposure mode) for settings of 2 to 20 seconds at f/2.8 to f/4 at ISO 400 to 1600. 

That’s a wide range, to be sure, but it will vary a lot depending on how bright the sky is at your site. Shoot at lots of different settings, as blending multiple exposures later in processing is often the best way to reproduce the scene as your eyes saw it. 

Shoot at a high ISO if you must to prevent blurring from sky motion. However, lower ISOs, if you can use them by choosing a slower shutter speed or wider lens aperture, will yield less digital noise.

Focus carefully on a bright star, as per the advice below for telephoto lenses. Don’t just set the lens focus to infinity, as that might not produce the sharpest stars.

Total Lunar Eclipse (December 20/21, 2010)
Total eclipse of the Moon, December 20/21, 2010, with 15mm lens at f/3.2 and Canon 5D MkII at ISO 1600 for a 1-minute tracked exposure. Without a tracker, use shorter exposures (less than 20 seconds) and higher ISOs or wider apertures to avoid trailing,

One scene to go for at this eclipse is similar to the above photo, with the reddened Moon above a winter landscape and shining east of Orion and the winter Milky Way. But that will require shooting from a dark site away from urban lights. But when the Moon is totally eclipsed, the sky will be dark enough for the Milky Way to appear. 

Framing Eclipse Sky
Click or tap on any of the charts to download a high-resolution copy.

The high altitude of the Moon at mid-eclipse from North America (with it 40 to 70 degrees above the horizon) will also demand a lens as wide as 10mm to 24mm, depending whether you use portrait or landscape orientation, and if your camera uses a cropped frame or full frame sensor. The latter have the advantage in this category of wide-angle nightscape. 

Framing Winter Milky Way & Moon

Alternatively, using a longer 14mm to 35mm lens allows you to frame the Moon beside Orion and the winter Milky Way, as above, but without the landscape. Again, this will require a dark rural site.

If you take this type of image with a camera on a fixed tripod, use high ISOs to keep exposures below 10 to 20 seconds to avoid star trailing. You have an hour of totality to shoot lots of exposures to make sure some will work best.

Total Lunar Eclipse, Dec 20, 2010 24mm Wide-Angle
Total eclipse of the Moon, December 20/21, 2010, with Canon 5D MKII and 24mm lens at f2.8 for stack of four 2-minute exposures at ISO 800. Taken during totality using a motorized sky tracker. The eclipsed Moon is the red object above Orion, and the stars appear bloated due to high haze and fog rolling in.

If you have a sky tracker to follow the stars, as I did above, exposures can be much longer — perhaps a minute to pick up the Milky Way really well — and ISOs can be lower to avoid noise. 

Option 1 Variation — Urban Eclipses

Unfortunately, point-and-shoot cameras and so-called “bridge” cameras, ones with non-interchangeable lenses, likely won’t have lenses wide enough to capture the whole scene, landscape and all. Plus their sensors will be noisy when used at high ISOs. Those cameras might be best used to capture moderate telephoto closeups at bright urban sites. 

With any camera, at urban sites look for scenic opportunities to capture the eclipsed Moon above a skyline or behind a notable landmark. By looking up from below you might be able to frame the Moon beside a church spire, iconic building, or a famous statue using a normal or short telephoto lens, making this a good project for those without ultra-wide lenses.

Total Lunar Eclipse, Feb. 20, 2008
Lunar eclipse, Feb 20, 2008 with a 135mm telephoto and Canon 20Da camera showing the Moon’s size with such a lens and cropped-frame camera. This is a blend of 8-second and 3-second exposures to bring out stars and retain the Moon. Both at ISO200 and f/2.8. Saturn is at lower left and Regulus at upper right.

Whatever your lens or subject, at urban sites expose as best you can for the foreground, trying to avoid any bright and bare lights in the frame that will flood the image with lens flares in long exposures. 

Capturing such a scene during the deep partial phases might produce a brighter Moon that stands out better in an urban sky than will a photo taken at mid-totality when the Moon is darkest. 

TIP: Practice, Practice, Practice!

With any camera, especially beginner point-and-shoots, ensure success on eclipse night by practicing shooting the Moon before the eclipse, during the two weeks of the waxing Moon leading up to Full Moon night and the eclipse.

The crescent Moon with Earthshine on the dark side of the Moon is a good stand-in for the eclipsed Moon. Set aside the nights of January 8 to 11 to shoot the crescent Moon. Check for exposure and focus. Can you record the faint Earthshine? It’s similar in brightness to the shadowed side of the eclipsed Full Moon.

The next week, on the nights of January 18 and 19, the waxing gibbous Moon will be closer to its position for eclipse night and almost as bright as the uneclipsed Full Moon, allowing some rehearsals for shooting it near a landmark.

Option 2: Advanced — Multiple Exposures

An advanced method is to compose the scene so the lens frames the entire path of the Moon for the 3 hours and 16 minutes from the start to the end of the partial eclipse. 

Framing TL-Start of Eclipse
This set of 3 charts shows the position of the Moon at the start, middle, and end of the eclipse, for planning lens choice and framing of the complete eclipse path. The location is Alberta, Canada.

Framing TL-Mid-Eclipse

Framing TL-End of Eclipse

As shown above, including the landscape will require at least a 20mm lens on a full frame camera, or 12mm lens on a cropped frame camera. However, these charts are for my site in western Canada. From sites to the east and south where the Moon is higher an even wider lens might be needed, making this a tough sequence to take.

With wide lenses, the Moon will appear quite small. The high altitude of the Moon and midnight timing won’t lend itself to this type of multiple image composite as well as it does for eclipses that happen near moonrise or moonset, as per the example below. 

Lunar Eclipse From Beginning to End, To True Scale
This is a multiple-exposure composite of the total lunar eclipse of Sunday, September 27, 2015, as shot from Writing-on-Stone Provincial Park, Alberta, Canada. For this still image composite of the eclipse from beginning to end, I selected just 40 frames taken at 5-minute intervals, out of 530 I shot in total, taken at 15- to 30-second intervals for the full time-lapse sequence included below.

A still-image composite with the lunar disks well separated will need shots only every 5 minutes, as I did above for the September 27, 2015 eclipse. 

Exposures for any lunar eclipse are tricky, whether you are shooting close-ups or wide-angles, because the Moon and sky change so much in brightness. 

As I did for the image below, for a still-image composite, you can expose just for the bright lunar disk and let the sky go dark.

Exposures for just the Moon will range from very short (about 1/500th second at f/8 and ISO 100) for the partials, to 1/2 to 2 seconds at f/2.8 to f/4 and ISO 400 for the totals, then shorter again (back to 1/500 at ISO 100) for the end shots when the Full Moon has returned to its normal brilliance. 

That’ll take constant monitoring and adjusting throughout the shoot, stepping the shutter speed gradually longer thorough the initial partial phase, then shorter again during the post-totality partial phase.

You’d then composite and layer (using a Lighten blend mode) the well-exposed disks (surrounded by mostly black sky) into another background image exposed longer for 10 to 30 seconds at ISO 800 to 1600 for the sky and stars, shot at mid-totality.

To maintain the correct relative locations of the lunar disks and foreground, the camera cannot move.

Lunar Eclipse Sequence from Monument Valley
The total lunar eclipse of April 4, 2015 taken from near Tear Drop Arch, in western Monument Valley, Utah. I shot the totality images during the short 4 minutes of totality. The mid-totality image is a composite of 2 exposures: 30 seconds at f/2.8 and ISO 1600 for the sky and landscape, with the sky brightening blue from dawn twilight, and 1.5 seconds at f/5.6 and ISO 400 for the disk of the Moon itself. Also, layered in are 26 short exposures for the partial phases, most being 1/125th sec at f/8 and ISO 400, with ones closer to totality being longer, of varying durations.

That technique works best if it’s just a still image you are after, such as above. This image is such a composite, of the April 4, 2015 total lunar eclipse from Monument Valley, Utah.

This type of composite takes good planning and proper exposures to pull off, but will be true to the scene, with the lunar disk and its motion shown to the correct scale and position as it was in the sky. It might be a composite, but it will be accurate.

My Rant! 

That’s in stark contrast to the flurry of ugly “faked” composites that will appear on the web by the end of the day on January 21, ones with huge telephoto Moons pasted willy-nilly onto a wide-angle sky.

Rather than look artistic, most such attempts look comically cut-and-pasted. They are amateurish. Don’t do it!  

Option 3: Advanced — Wide-Angle Time-Lapses

If it’s a time-lapse movie you want (see the video below), take exposures every 10 to 30 seconds, to ensure a final movie with smooth motion.

Unlike shooting for a still-image composite, for a time lapse each frame will have to be exposed well enough to show the Moon, sky, and landscape. 

That will require exposures long enough to show the sky and foreground during the partial phases — likely about 1 to 4 seconds at f/2.8 and ISO 400. In this case, the disk of the partially-eclipsed Moon will greatly overexpose, as it does toward the end of the above time-lapse from September 27, 2015.. 

But the Moon will darken and become better exposed during the late stages of the partial eclipse and during totality when a long exposure — perhaps now 10 to 20 seconds at f/2.8 and ISO 800 to 1600 — will record the bright red Moon amid the stars and winter Milky Way. 

Maintaining a steady cadence during the entire sequence requires using an interval long enough throughout to accommodate the expected length of the longest exposure at mid-totality, with similar camera settings to what you’ve used for other Milky Way nightscapes. If you’ve never taken those before, then don’t attempt this complex sequence. 

After totality, as the Moon and sky re-brighten, exposures will have to shorten again, and  symmetrically in reverse fashion for the final partial phases.

Such a time-lapse requires consistently and incrementally adjusting the camera over the three or more hours of the eclipse on a cold winter night. The high altitude of the Moon and its small size on the required wide angle lenses will make any final time lapse less impressive than at eclipses that occur when the Moon is rising or setting. 

But … the darkening of the sky and “turning on” of the Milky Way during totality will make for an interesting time-lapse effect. The sky and scene will be going from a bright fully moonlit night to effectively a dark moonless night, then back to moonlit. It’s a form of “holy grail” time lapse, requiring advanced processing with LRTimelapse software. 

Again, do not move the camera. Choose your lens and frame your camera to include the entire path of the Moon for as long as you plan to shoot. 

Even if the final movie looks flawed, individual frames should still produce good still images, or a composite built from a subset of the frames. 

Option 4: Simple — Telephoto Close-Ups

The first thought of many photographers is to shoot the eclipse with as long a telephoto lens as possible. That can work, but …

The harsh reality is that the Moon is surprisingly small (only 1/2-degree across) and needs a lot of focal length to do it justice, if you want a lunar close-up.

Telescope FOV-400 & 800mm

You’ll need a 300mm to 800mm lens. Unfortunately, the Moon and sky are moving and any exposures over 1/4 to 2 seconds (required during totality) will blur the Moon badly if its disk is large on the frame and all you are using is a fixed tripod.

If you don’t have a tracking mount, one solution is to keep the Moon’s disk small (using no more than a fast f/2 or f/2.8 135mm to 200mm lens) and exposures short by using a high ISO speed of 1600 to 3200. Frame the Moon beside the Beehive star cluster as I show below.

Take a range of exposures. But … be sure to focus!

TIP: Focus! And Focus Again!

Take care to focus precisely on a bright star using Live View. That’s true of any lens but especially telephotos and telescopes. 

Focus not just at the start of the night, but also more than once again later at night. Falling temperatures on a winter night will cause long lenses and telescopes to shift focus. What was sharp at the start of the eclipse won’t be by mid totality. 

The catch is that if you are shooting for a time-lapse or composite you likely won’t be able to re-point the optics to re-focus on a star in mid-eclipse. In that case, be sure to set up the gear well before you want to start shooing to let it cool to ambient air temperature. Now focus on a star, then frame the scene. Then hope the lens doesn’t shift off focus. You might be able to focus on the bright limb of the Moon but it’s risky.

Fuzzy images, not bad exposures, are the ruin of most attempts to capture a lunar eclipse, especially with a telephoto lens. And the Moon itself, especially during totality, is not a good target to focus on. Use a bright star. The winter sky has lots!

Option 5: Advanced — Tracked Telescopic Close-Ups 

If you have a mount that can be polar aligned to track the sky, then many more options are open to you. 

Sigma on SAM on Stars

You can use a telescope mount or one of the compact and portable trackers, such as the Sky-Watcher Star Adventurer (I show the Mini model above) or iOptron Sky Tracker units. While these latter units work great, you are best to keep the payload weight down and your lens size well under 300mm. 

Framing Telephoto CU

That’s just fine for this eclipse, as you really don’t need a frame-filling Moon. The reason is that the Moon will appear about 6 degrees west of the bright star cluster called the Beehive, or Messier 44, in Cancer.

As shown above, a 135mm to 200mm lens will frame this unique pairing well. For me, that will be the signature photo of this eclipse. The pairing can happen only at lunar eclipses that occur in late January, and there won’t be any more of those until 2037! 

That’s the characteristic that makes this eclipse rare and unique, not that it’s a “super-duper, bloody, wolf Moon!” But it doesn’t make for a catchy headline.

Total Lunar Eclipse, Dec 20, 2010 Total HDR
A High Dynamic Range composite of 7 exposures of the Dec 20/21, 2010 total lunar eclipse, from 1/2 second to 30 seconds, to show the more normally exposed eclipsed Moon with the star cluster M35, at left, in Gemini, to show the scene as it appeared in binoculars. Each tracked photo taken with a 77mm Borg apo refractor at f/4.2 (300mm focal length) and Canon 5D MkII at ISO 1600.

Exposures to show the star cluster properly might have to be long enough (30 to 120 seconds) that the Moon overexposes, even at mid-totality. If so, take different exposures for the Moon and stars, then composite them later, as I did above for the December 20, 2010 eclipse near the Messier 35 star cluster in Gemini. 

If really you want to shoot with even more focal length for framing just the Moon, a monster telephoto lens will work, but a small telescope such as an 80mm aperture f/6 to f/7 refractor will provide enough focal length and image size at much lower cost and lighter weight, and be easier to attach to a telescope mount. 

But even with a 500mm to 800mm focal length telescope the Moon fills only a small portion of the frame, though cropped frame cameras have the advantage here. Use one if it’s a big Moon you’re after! 

No matter the camera, the lens or telescope should be mounted on a solid equatorial telescope mount that you must polar align earlier in the night to track the sky. 

Alternatively, a motorized Go To telescope on an alt-azimuth mount will work, but only for single shots. The rotation of the field with alt-az mounts will make a mess of any attempts to shoot multiple-exposure composites or time-lapses, described below. 

Whatever the mount, for the sharpest lunar disks during totality, use the Lunar tracking rate for the motor. 

Total Lunar Eclipse Exposure Series
This series shows the need to constantly shift exposure by lengthening the shutter speed as the eclipse progresses. Do the same to shorten the exposure after totality. The exposures shown here are typical. 

Assuming an f-ratio of f/6 to f/8, exposures will vary from as short as 1/250th second at ISO 100 to 200 for the barely eclipsed Moon, to 4 to 20 seconds at ISO 400 to 1600 for the Moon at mid-totality. 

It’s difficult to provide a precise exposure recommendation for totality because the brightness of the Moon within the umbra can vary by several stops from eclipse to eclipse, depending on how much red sunlight manages to make it through Earth’s atmospheric filter to light the Moon.

TIP: Shoot for HDR

Total Lunar Eclipse, Dec 20, 2010 Partial HDR
Total eclipse of the Moon, December 20/21, 2010, with 5-inch refractor at f/6 (780mm focal length) and Canon 7D (cropped frame camera) at ISO 400. This is an HDR blend of 9 images from 1/125 second to 2 seconds, composited in Photoshop. Note  the blue tint along the shadow edge.

As I did above, during the deep partial phases an option is to shoot both long, multi-second exposures for the red umbra and short, split-second exposures for the bright part of the Moon not yet in the umbra.

Take 5 to 7 shots in rapid succession, covering the range needed, perhaps at 1-stop increments. Merge those later with High Dynamic Range (HDR) techniques and software, or with luminosity masks. 

Even if you’re not sure how to do HDR processing now, shoot all the required exposures anyway so you’ll have them when your processing skills improve. 

Option 6: Advanced — Close-Up Composites and Time-Lapses

With a tracking telescope on an equatorial mount you could fire shots every 10 to 30 seconds, and then assemble them into a time-lapse movie, as below. 

But as with wide-angle time-lapses, that will demand constant attention to gradually and smoothly shift exposures, ideally by 1/3rd-stop increments every few shots during the partial and total phases. Make lots of small adjustments, rather than fewer large ones.

If you track at the lunar rate, as I did above, the Moon should stay more or less centred while it drifts though the stars, assuming your mount is accurately polar aligned, an absolutely essential prerequisite here.  

Lunar Eclipse Composite
Composite image digitally created in Photoshop of images taken during October 27, 2004 total lunar eclipse, from Alberta Canada. Images taken through 5-inch apo refractor at f/6 with Canon Digital Rebel 300D camera at ISO 200.

Conversely, track at the sidereal rate and the stars will stay more or less fixed while the Moon drifts through the frame from right to left (west to east) as I show above in a composite of the October 27, 2004 eclipse.

But such a sequence takes even more careful planning to position the Moon correctly at the start of the sequence so it remains “in frame” for the duration of the eclipse, and ends up where you want at the end.

In the chart below, north toward Polaris is at the top of the frame. Position the Moon at the start of the eclipse so it ends up just above the centre of the frame at mid-eclipse. Tricky! 

Telescope CU-Stages
Repeated from earlier, this chart shows the path of the Moon through the north half of the umbra, a path that will be the same for any site, as will be the timing. North is up here.

As I show above, for this type of “Moon-thru-shadow” sequence a focal length of about 400mm is ideal on a full frame camera, or 300mm on a cropped frame camera.

From such a time-lapse set you could also use several frames selected from key stages of the eclipse, as I did in 2004, to make up a multiple-image composite showing the Moon moving through the Earth’s shadow. 

Again, planetarium software such as Starry Night I used above, which can be set to display the field of view of the camera and lens of your choice, is essential to plan the shoot. Don’t attempt it without the right software to plan the framing. 

I would consider the telescopic time-lapse method the most challenging of techniques. Considering the hour of the night and the likely cold temperatures, your best plan might be to keep it simple. 

It’s what I plan to do.

I’ll be happy to get a tracked telephoto close-up of the Moon and Beehive cluster as my prime goal, with a wide-angle scene of the eclipsed Moon beside Orion and the Milky Way as a bonus. A few telescope close-ups will be even more of a bonus.

Astrospheric
The Astrospheric website, with astronomy-oriented weather predictions. It’s also available as a great mobile app.

However, just finding clear skies might be the biggest challenge!

Try the Astrospheric app for astronomy-oriented weather predictions. The Environment Canada data it uses has led me to clear skies for several recent eclipses that other observers in my area missed. 

It’ll be worth the effort to chase!

The next total eclipse of the Moon anywhere on Earth doesn’t occur until May 26, 2021 in an event visible at dawn from Western North America. The next total lunar eclipse visible from all of North America comes a lunar year later, on May 15, 2022. 

Total Lunar Eclipse from Alan Dyer on Vimeo.

I leave you with a music video of the lunar eclipse of September 27, 2015 that incorporates still and time-lapse sequences shot using all of the above methods. 

Good luck and clear skies on eclipse night!

— Alan, January 1, 2019 / © 2019 Alan Dyer / amazingsky.com 

 

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The Fast 14s Face-Off


Sigma and Rokinon 14mm on Stars

I put two new fast 14mm lenses to the test: the Sigma 14mm f/1.8 Art vs. the Rokinon 14mm f/2.4 SP. 

Much to the delight of nightscape and astrophotographers everywhere we have a great selection of new and fast wide-angle lenses to pick from.

Introduced in 2017 are two fast ultra-wide 14mm lenses, from Sigma and from Rokinon/Samyang. Both are rectilinear, not fish-eye, lenses.

I tested the Nikon version of the Sigma 14mm f/1.8 Art lens vs. the Canon version of the Rokinon 14mm f/2.4 SP. I used a Nikon D750 and Canon 6D MkII camera.

I also tested the new faster Rokinon SP against the older and still available Rokinon 14mm f/2.8, long a popular lens among nightscape photographers.

The Sigma 14mm is a fully automatic lens with auto focus. It is the latest in their highly regarded Art series of premium lenses. I have their 20mm and 24mm Art lenses and love them.

The Rokinon 14mm SP (also sold under the Samyang brand) is a manual focus lens, but with an AE chip so that it communicates with the camera. Adjusting the aperture is done on the camera, not by turning a manual aperture ring, as is the case with many of Rokinon’s lower cost series of manual lenses. The lens aperture is then recorded in each image’s EXIF metadata, an aid to later processing. It is part of Rokinon’s premium “Special Performance” SP series which includes an 85mm f/1.2 lens.

All units I tested were items purchased from stock, and were not supplied by manufacturers as samples for testing. I own these!

CONCLUSIONS

For those with no time to read the full review, here are the key points:

• The Sigma f/1.8 Art exhibits slightly more off-axis aberrations than the Rokinon 14mm SP, even at the same aperture. But aberrations are very well controlled.

• As its key selling point, the Sigma offers another full stop of aperture over the Rokinon SP (f/1.8 vs. f/2.4), making many types of images much more feasible, such as high-cadence aurora time-lapses and fixed-camera stills and time-lapses of a deeper, richer Milky Way.

• The Sigma also has lower levels of vignetting (darkening of the frame corners) than the Rokinon 14mm SP, even at the same apertures.

• Both the Sigma Art and Rokinon SP lenses showed very sharp star images at the centre of the frame.

• Comparing the new premium Rokinon 14mm SP against the older Rokinon 14mm f/2.8 revealed that the new SP model has reduced off-axis aberrations and lower levels of vignetting than the lower-cost f/2.8 model. However, so it should for double the price or more of the original f/2.8 lens.

• The Rokinon 14mm SP is a great choice for deep-sky imaging where optical quality is paramount. The Sigma 14mm Art’s extra speed will be superb for time-lapse imaging where the f/1.8 aperture provides more freedom to use shorter shutter speeds or lower ISO settings.

• Though exhibiting the lowest image quality of the three lenses, the original Rokinon 14mm f/2.8 remains a superb value, at its typical price of $350 to $500. For nightscapers on a budget, it’s an excellent choice.

 

TESTING PROCEDURES

For all these tests I placed the camera and lens on a tracking mount, the Sky-Watcher Star Adventurer Mini shown below. This allowed the camera to follow the sky, preventing any star trailing. Any distortions you see are due to the lens, not sky motion.

Sigma on SAM on Stars
Star Adventurer Mini Tracker (with Sigma 14mm on Nikon D750)

As I stopped down the aperture, I lengthened the exposure time to compensate, so all images were equally well exposed.

In developing the Raw files in Adobe Camera Raw, I applied a standard level of Contrast (25) and Clarity (50) boost, and a modest colour correction to neutralize the background sky colour. I also applied a standard level of noise reduction and sharpening.

However, I did not apply any lens corrections that, if applied, would reduce lateral chromatic aberrations and compensate for lens vignetting.

So what you see here is what the lens produced out of the camera, with no corrections. Keep in mind that the vignetting you see can be largely compensated for in Raw development, with the provisos noted below. But I wanted to show how much vignetting each lens exhibited.

OFF-AXIS ABERRATIONS

Stars are the severest test of any lens. Not test charts, not day shots of city skylines. Stars.

The first concern with any fast lens is how sharp the stars are not only in the centre of the frame, but also across the frame to the corners. Every lens design requires manufacturers to make compromises on what lens aberrations they are going to suppress at the expense of other lens characteristics. You can never have it all!

However, for astrophotography we do look for stars to be as pinpoint as possible to the corners, with little coma and astigmatism splaying stars into seagull and comet shapes. Stars should also not become rainbow-coloured blobs from lateral chromatic aberration.

SIGMA 14mm ART

Sigma 14mm Upper L Corner
Sigma 14mm Art – Upper Left Corner Close-up at 5 Apertures

Sigma 14mm Upper R Corner
Sigma 14mm Art – Upper Right Corner Close-up at 5 Apertures

These images show 200% blowups of the two upper corners of the Sigma 14mm Art lens, each at five apertures, from wide open at f/1.8, then stopped down at 1/3rd stop increments to f/2.8. As you would expect, performance improves as you stop down the lens, though some astigmatism and coma are still present at f/2.8.

But even wide open at f/1.8, off-axis aberrations are very well controlled and minimal. You have to zoom up this much to see them.

There was no detectable lateral chromatic aberration.

Aberrations were also equal at each corner, showing good lens centering and tight assembly tolerances.

ROKINON 14mm SP

Rokinon 14mm Upper L Corner
Rokinon 14mm SP at 3 Apertures

Rokinon 14mm Upper R Corner
Rokinon 14mm SP at 3 Apertures

Similarly, these images show 200% blow-ups of the upper corners of the Rokinon SP, at its three widest apertures: f/2.4, f/2.8 and f/3.2.

Star images look tighter and less aberrated in the Rokinon, even when compared at the same apertures.

But images look better on the left side of the frame than on the right, indicating a slight lens de-centering or variation in lens position or figuring, a flaw noted by other users in testing Rokinon lenses. The difference is not great and takes pixel-peeping to see. Nevertheless, it is there, and may vary from unit to unit. This should not be the case with any “premium” lens.

SIGMA vs. ROKINON

Rokinon vs Sigma (Corner Aberrations)
Rokinon vs. Sigma Corner Aberrations Compared

This image shows both lenses in one frame, at the same apertures, for a more direct comparison. The Rokinon SP is better, but of course, doesn’t go to f/1.8 as does the Sigma.

ON-AXIS ABERRATIONS

We don’t want good performance at the corners if it means sacrificing sharp images at the centre of the frame, where other aberrations such as spherical aberration can take their toll and blur images.

These images compare the two lenses in 200% blow-ups of an area in the Cygnus Milky Way that includes the Coathanger star cluster. Both lenses look equally as sharp.

SIGMA 14mm ART

Sigma 14mm Centre
Sigma 14mm Art – Centre of Frame Close-up

Even when wide open at f/1.8 the Sigma Art shows very sharp star images, with little improvement when stopped down. Excellent!

ROKINON 14mm SP

Rokinon 14mm Centre
Rokinon 14mm SP – Centre of Frame Close-up

The same can be said for the Rokinon SP. It performs very well when wide open at f/2.4, with star images as sharp as when stopped down 2/3rds of an f-stop to f/3.2

SIGMA vs. ROKINON

Rokinon vs Sigma (Centre Aberrations)
Sigma vs. Rokinon Centre Sharpness Compared

This image shows both lenses in one frame, but with the Sigma wide open at f/1.8 and stopped down to f/2.8, vs. the Rokinon wide open at f/2.4 and stopped to f/2.8. All look superb.

VIGNETTING

The bane of wide-angle lenses is the light fall-off that is inevitable as lens focal lengths decrease. We’d like this vignetting to be minimal. While it can be corrected for later when developing the Raw files, doing so can raise the visibility of noise and discolouration, such as magenta casts. The less vignetting we have to deal with the better.

As with off-axis aberrations, vignetting decreases as lenses are stopped down. Images become more uniformly illuminated across the frame, with less of a “hot spot” in the centre.

SIGMA 14mm ART

Sigma 14mm Vignetting (5 Apertures)
Sigma 14mm Art – Vignetting Compared at 5 Apertures

This set compares the left edge of the frame in the Sigma SP at five apertures, from f/1.8 to f/2.8. You can see how the image gets brighter and more uniform as the lens is stopped down. (The inset image at upper right show what part of the frame I am zooming into.)

ROKINON 14mm SP

Rokinon 14mm Vignetting (3 Apertures)
Rokinon 14mm SP – Vignetting Compared at 3 Apertures

This similar set compares the frame’s left edge in the Rokinon SP at its three widest apertures, from f/2.4 to f/3.2. Again, vignetting improves but is still present at f/3.2.

SIGMA vs. ROKINON

Rokinon vs Sigma Vignetting
Rokinon vs. Sigma – Vignetting Compared

This compares both lenses at similar apertures side by side for a direct comparison. The Sigma is better than the Rokinon with a much more uniform illumination across the frame.

Sigma 14mm Vignetting at f1.8
Sigma 14mm Art – Vignetting at f/1.8 Maximum Aperture

Rokinon 14mm Vignetting at f2.4
Rokinon 14mm SP – Vignetting at f/2.4 Maximum Aperture

In these two images, above, of the entire frame at their respectively widest apertures, I’d say the Sigma exhibits less vignetting than the Rokinon, even when wide open at f/1.8. The cost for this performance, other than in dollars, is that the Sigma is a large, heavy lens with a massive front lens element.

ROKINON 14mm f/2.4 SP vs. ROKINON 14mm f/2.8 Standard

Even the Rokinon 14mm SP, though a manual lens, carries a premium price, at $800 to $1000 U.S., depending on the lens mount.

Samyang 14mm Lens
The 14mm Rokinon/Samyang f/2.8 Lens

For those looking for a low-cost, ultra-wide lens, the original Rokinon/Samyang 14mm f/2.8 (shown above) is still available and popular. It is a fully manual lens, though versions are available with a AE chip to communicate lens aperture information to the camera.

I happily used this f/2.8 lens for several years. Before I sold it earlier in 2017 (before I acquired the Sigma 14mm), I tested it against Rokinon’s premium SP version.

The older f/2.8 lens exhibited worse off-axis and on-axis aberrations and vignetting than the SP, even with the SP lens set to the same f/2.8 aperture. But image quality of the original lens is still very good, and the price is attractive, at half the price or less, than the 14mm SP Rokinon.

TWO 14mm ROKINONS: OFF-AXIS ABERRATIONS

14mm Rokinons Aberrations (Upper L Corner)
Two Rokinons (Older “Standard” vs. new SP) – Upper Left Corner Close-up

14mm Rokinons Aberrations (Upper R Corner)
Two Rokinons (Older “Standard” vs. new SP) – Upper Right Corner Close-up

Here, in closeups of the upper corners, I show the difference between the two Rokinons, the older standard lens on the left, and the new SP on the right.

The SP, as it should, shows lower aberrations and tighter star images, though with the improvement most marked on the left corner; not so much on the right corner. The original f/2.8 lens holds its own quite well.

TWO 14mm ROKINONS: ON-AXIS ABERRATIONS

14mm Rokinons Aberrations (Centre)
Two Rokinons (Older “Standard” vs. new SP) – Centre of Frame Close-up

At the centre of the frame, the difference is more apparent, with the SP lens exhibiting sharper star images than the old 14mm with its generally softer, larger star images. The latter likely has more spherical aberration.

TWO 14mm ROKINONS: VIGNETTING

14mm Rokinons Vignetting
Two Rokinons (Older “Standard” vs. new SP) – Vignetting Compared

The new SP lens clearly has the advantage here, with less vignetting and brighter corners even when wide open at f/2.4 than the older lens does at its widest aperture of f/2.8. This is another reason to go for the new SP if image quality is paramount

PRICES

The new Sigma 14mm Art lens is costly, at $1600 U.S., though with a price commensurate with its focal length and aperture. Other premium lenses in this focal length range, either prime or zoom, from Nikon and Canon sell for much more, and have only an f/2.8 maximum aperture. So in that sense, the Sigma Art is a bargain.

The new Rokinon 14mm SP sells for $800 to $1000, still a premium price for a manual focus lens. But its optical quality competes with the best.

The older Rokinon 14mm f/2.8 is a fantastic value at $350 to $500, depending on lens mount and AE chip. For anyone getting into nightscape and Milky Way photography, it is a great choice.

RECOMMENDATIONS

With such a huge range in price, what should you buy?

A 14mm is a superb lens for nightscape shooting – for sky-filling auroras, for panoramas along the Milky Way, or of the entire sky. But the lens needs to be fast. All three lenses on offer here satisfy that requirement.

Sigma 14mm & Rokinon 14mm SP (Front)
Sigma 14mm Art (left) and Rokinon 14mm SP (right)

SIGMA 14mm f/1.8 ART

If you want sheer speed, this is the lens. It offers a full stop gain over the already fast Rokinon f/2.5, allowing exposures to be half the length, or shooting at half the ISO speed for less noise.

Its fast speed comes into its own for rapid cadence aurora time-lapses, to freeze auroral motion as much as possible in exposures as short as 1 to 2 seconds at a high ISO. The fast speed might also make real-time movies of the aurora possible on cameras sensitive and noiseless enough to allow video shooting at ISO 25,000 and higher, such as the Sony a7s models.

The Sigma’s fast speed also allows grabbing rich images of the Milky Way in exposures short enough to avoid star trailing, either in still images or in time-lapses of the Milky Way in motion.

While the Sigma does exhibit some edge aberrations, they are very well controlled (much less than I see with some 24mm and 35mm lenses I have) and are a reasonable tradeoff for the speed and low level of vignetting, which results in less noisy corners.

Photographers obsess over corner aberrations when, for fixed-camera nightscape shooting, a low level of vignetting is probably more critical. Correcting excessive vignetting introduces noise, while the corner aberrations may well be masked by star trailing. Only in tracked images do corner aberrations become more visible, as in the test images here.

I’d suggest the Sigma is the best choice for nightscape and time-lapse shooting, with its speed allowing for kinds of shots not possible otherwise.

The Sigma also appears to be the best coated of all the lenses, as you can see in the reflections in the lenses in the opening image, and below. However, I did not test the lenses for flares and ghosting.

As a footnote, none of the lenses allow front-mounted filters, and none have filter drawers.

ROKINON 14mm f/2.4 SP

For less money you get excellent optical quality, though with perhaps some worrisome variation in how well the lens elements are figured or assembled, as evidenced by the inconsistent level of aberration from corner to corner.

Nevertheless, stars are tight on- and off-axis, and vignetting is quite low, for corners that will be less noisy when the shadows are recovered in processing.

I’d suggest the Rokinon SP is a great choice if tracked deep-sky images are your prime interest, where off-axis performance is most visible. However, the SP’s inconsistent aberrations from corner to corner are evidence of lower manufacturing tolerances than Sigma’s, so your unit may not perform like mine.

For nightscape work, the SP’s f/2.4 aperture might seem a minor gain over Rokinon’s lower-cost f/2.8 lens. But it is 1/3 of an f-stop. That means, for example, untracked Milky Way exposures could be 30 seconds instead of 40 seconds, short enough to avoid obvious star trailing. At night, every fraction of an f-stop gain is welcome and significant.

ROKINON 14mm f/2.8 Standard

You might never see the difference in quality between this lens and its premium SP brother in images intended for time-lapse movies, even at 4K resolution.

But those intending to do long-exposure deep-sky imaging, as these test images are, will want the sharpest stars possible across the frame. In which case, consider the 14mm SP.

But if price is a prime consideration, the original f/2.8 Rokinon is a fine choice. You’ll need to apply a fair amount of lens correction in processing, but the lens exists in the Camera Raw/Lightroom database, so correction is just a click away.

Sigma and Rokinon 14mm on Stars

That was a lengthy report, I know! But there’s no point in providing recommendations without the evidence to back them up.

All images, other than the opening “beauty shot,” can be clicked/tapped on to download a full-resolution original JPG for closer inspection.

As I’ve just received the Sigma Art lens I’ve not had a chance to shoot any “real” nightscape images with it yet, just these test shots. But for a real life deep-sky image of the Milky Way shot with the Rokinon SP, see this image from Australia. https://flic.kr/p/SSQm7G

I hope you found the test of value in helping you choose a lens.

Clear skies!

— Alan, September 22, 2017 / © 2017 Alan Dyer / amazingsky.com

 

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Last of the Summer Milky Way


Last of the Summer Milky Way

The summer Milky Way sets into the southwest on a late November night. 

On Saturday, November 28, well into winter here in Alberta, the stars of the Summer Triangle and the summer Milky Way set into the southwest on a clear, though slightly hazy, late November night.

This is the last of the summer Milky Way, with the centre of the Galaxy now long gone, but the Summer Triangle stars remaining in the evening sky well into autumn. Glows from light pollution in the west light the horizon, in a quick series of images shot in my rural backyard.

In the Summer Triangle, Vega is at right, as the brightest star; Deneb is above centre, and Altair is below centre, farthest south in the Milky Way.

I shot this as a test image for the Nikkor 14-24mm lens, here wide-open at f/2.8 and at 14mm, where it performs beautifully, with very tight star images to the corners. It does very well at 24mm, too! This is astonishing performance for a zoom lens. It matches or beats many “prime” lenses for quality.

The camera was the 36-megapixel Nikon D810a, Nikon’s “astronomical DSLR” camera, also on test. Here it shows its stuff by picking up the red nebulas in Cygnus and Cepheus.

Thorough tests of both the camera and lens will appear later in the year. Stay tuned.

Do subscribe to my blog (click below) to get email notices of new entries.

For the even more technically-minded, this image is a stack, mean combined, of five 2-minute tracked exposures, at f/2.8 and ISO 800. The camera was on the iOptron Sky-Tracker. So the stars are not trailed but the ground is! I made no attempt here to layer in an untracked ground shot, as there isn’t much detail of interest worth showing, quite frankly.

At least not in the ground. But the Milky Way is always photogenic.

– Alan, November 28, 2015 / © 2015 Alan Dyer / www.amazingsky.com

 

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