Testing the Canon R5 for Astrophotography


In a format similar to my other popular camera tests, I put the 45-megapixel Canon R5 mirrorless camera through its paces for the demands of astrophotography. 

In a sequel to my popular post from September 2021 where I reviewed the Canon R6 mirrorless camera, here is a similar test of its higher-megapixel companion, the Canon R5. Where the R6 has a modest 20-megapixel sensor with relatively large 6.6-micron pixels, the R5 is (at present) Canon’s highest megapixel camera, with 45 megapixels. Each pixel is only 4.4 microns across, providing higher resolution but risking more noise. 

Is the higher noise noticeable? If so, does that make the R5 less than ideal for astrophotography? To find out, I tested an R5 purchased locally in Calgary from The Camera Store in May 2022. 

NOTE: CLICK orTAP on any image to bring it up full screen for closer inspection. The blog contains a lot of high-res images, so they may take a while to all load. Patience! Thanks! 

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


The Canon R5 uses a full-frame sensor offering 45 megapixels, producing images with 8192 x 5464 pixels, and making 8K video possible.

TL;DR Summary

The Canon R5 proved to be surprisingly low in noise, and has worked very well for nightscape, lunar and deep-sky photography (as shown below), where its high resolution does produce a noticeable improvement to image detail, with minimal penalty from higher noise. Its 8K video capability has a place in shooting the Moon, Sun and solar eclipses. It was not so well suited to shooting videos of auroras. 

This is a stack of 12 x 5-minute exposures with a Sharpstar 94EDPH refractor at f/4.5 and the Canon R5 at ISO 800, taken as a test of the R5 for deep-sky imaging. No filters were employed. Close-ups of sub-frames from this shoot with the R5, and also with the R6 and Ra, are used throughout the review.

R5 Pros

The Canon R5 is superb for its:

  • High resolution with relatively low noise
  • ISO invariant sensor performance for good shadow recovery 
  • Good live view display with ISO boost in Movie mode 
  • 8K video has its attraction for eclipse photography
  • Good top LCD information screen missing in the R6
  • No magenta edge “amp glow” that the R6 shows
  • Higher 6x and 15x magnifications for precise manual focusing
  • Good battery life 
  • Pro-grade Type N3 remote port

R5 Cons

The Canon R5 is not so superb for its:

  • Noise in stills and movies is higher than in the R6
  • Propensity for thermal-noise hot pixels in shadows
  • Not so suitable for low-light video as the R6
  • Overheating in 8K video
  • Live View image is not as bright as in the R6’s Movie mode
  • High cost! 

The flip-out screen of the R5 (and all recent Canon cameras) requires an L-bracket with a notch in the side (a Small Rig unit is shown here) to accommodate the tilting screen.  

CHOOSING THE R5

Since late 2019 my main camera for all astrophotography has been the Canon Ra, a limited-edition version of the original R, Canon’s first full-frame mirrorless camera that started the R series. The Ra had a special infra-red cutoff filter in front of the sensor that passed a higher level of visible deep-red light, making it more suitable for deep-sky astrophotography than a standard DSLR or DSLM (mirrorless) camera. The Ra was discontinued after two years on the market, a lifetime similar to Canon’s previous astronomical “a” models, the 20Da and 60Da. 

I purchased the Canon R6 in late 2021, primarily to use it as a low-light video camera for aurora photography, replacing the Sony a7III I had used for several years and reviewed here. Over the last year, I sold all my non-Canon cameras, as well as the Canon 6D MkII DSLR (reviewed here), to consolidate my camera gear to just Canon mirrorless cameras and lenses. 

The R6 has proven to be an able successor to the Sony for me, with the R6’s modest megapixel count and larger pixels making it excellent for low-light video. But the higher resolution of the R5 was still attractive. So I have now added it to my Canon stable. Since doing so, I have put it through several of my standard tests to see how suitable it is for the demands of astrophotography, both stills and video. 

Here are my extensive results, broken down by various performance criteria. I hope you will find my review useful in helping you make a purchase decision.


LIVE VIEW FRAMING

This compares the back-of-camera views of the R5 vs. the R6, with both set to their highest ISO in Movie mode for the brightest preview image.

First, why go mirrorless at all? For astrophotography, the big difference compared to even a high-end DSLR, is how much brighter the “Live View” image is when shooting at night. DSLM cameras are always in Live View – even the eye-level viewfinder presents a digital image supplied by the sensor. 

And that image is brighter, often revealing more than what a DSLR’s optical viewfinder can show, a great advantage for framing nightscape scenes, and deep-sky fields at the telescope.

The R5 certainly presents a good live view image. However, it is not as bright nor as detailed as what the R6 can provide when placed in its Movie mode and with the ISO bumped up to the R6’s highest level of ISO 204,800, where the Milky Way shows up, live! 

The R5 only goes as high as ISO 51,200, and so as I expected it does not provide as bright or detailed a preview at night as the R6 can. However, the R5 is better than the original R for live-view framing, and better than any Canon DSLR I’ve used. 


LIVE VIEW FOCUSING

As with other Canon mirrorless cameras, the R5 offers a Focus Assist overlay (top) to aid manual focusing. It works on bright stars. It also has a 6x and 15x magnifications for even more precise focusing.

Like the R6, the R5 can autofocus accurately on bright stars and planets. By comparison, while the Ra can autofocus on distant bright lights, it fails on bright stars or planets. 

Turning on Focus Peaking makes stars turn red, yellow or blue (your choice of colours) when they are in focus, as a reassuring confirmation. 

Turning on Focus Guide provides the arrowed overlays shown above.

In manual focus, an additional Focus Aid overlay, also found in the R6, provides arrows that close up and turn green when in focus on a bright star or planet. 

Or, as shown above, you can zoom in by 6x or 15x to focus by eye the old way by examining the star image. These are magnification levels higher than the 5x and 10x of the R6 and most other Canon cameras, and are a great aid to precise focusing, necessary to make full use of the R5’s high resolution, and the sharpness of Canon’s RF lenses. The 15x still falls short of the Ra’s 30x for ultra-precise focusing on stars, but it’s a welcome improvement nonetheless. 

In all, while the R5 is not as good as the R6 for framing in low light, it is better for precise manual focusing using its higher 15x magnification. 


NOISE PERFORMANCE — NIGHTSCAPES

The key camera characteristic for astrophoto use is noise. There is no point in having lots of resolution if, at the high ISOs we use for most astrophotography, the detail is lost in noise. But I was pleasantly surprised that proved not to be the case with the R5.

As I show below, noise is well controlled, making the R5 usable for nightscapes at ISOs up to 3200, if not 6400 when needed in a pinch. 

This compares the noise on a dark nightscape at the typical ISOs used for such scenes. A level of noise reduction shown has been applied in Camera Raw. 

With 45 megapixels, at the upper end of what cameras offer today, the R5 has individual pixels, or more correctly “photosites,” that are each 4.4 microns in size, the “pixel pitch.” 

This is still larger than the 3.7-micron pixels in a typical 24-megapixel cropped-frame camera like the Canon R10, or the 3.2-micron pixels found in a 32-megapixel cropped-frame camera like the Canon R7. Both are likely to be noisier than the R5, though will provide even higher resolution, as well as greater magnification with any given lens or telescope. 

By comparison, the 30-megapixel full-frame R (and Ra) has a pixel pitch of 5.4 microns, while the 20-megapixel R6’s pixel pitch is a generous 6.6 microns. Only the 12-megapixel Sony a7SIII has larger 8.5-micron pixels, making it the low-light video champ.

The bigger the photosites (i.e. the larger the pixel pitch), the more photons each photosite can collect in a given amount of time – and the more photons they can collect, period, before they overfill and clip highlights. More photons equals more signal, and therefore a better signal-to-noise ratio, while the greater “full-well depth” yields higher dynamic range. 

However, each generation of camera improves the signal-to-noise ratio by suppressing noise via its sensor design and improved signal processing hardware and firmware. The R5 and R6 each use Canon’s latest DIGIC X processor. 

This compares the R5 to the R6 and Ra cameras at the high ISOs of 3200 and 6400 often used for Milky Way nightscapes. 

In nightscapes the R5 did show more noise at high ISOs, especially at ISO 6400, than the R6 and Ra, but the difference was not large, perhaps one stop at most, if that. What was noticeable was the presence in the R5 of more hot pixels from thermal noise, as described later. 

This compares the R5 to the R6 and Ra cameras at the more moderate ISOs of 800 and 1600 used for brighter nightscapes. 

At slower ISOs the R5 showed a similar level of noise as the R6 and Ra, but a finer-grained noise than the R6, in keeping with the R5’s smaller pixels. In this test set, the R5 did not exhibit noticeably more noise than the other two cameras. This was surprising.

NOTE: In these comparisons I have not resampled the R5 images down to the megapixel count of the R6 to equalize them, as that’s not what you would do if you bought an R5. Instead, I have magnified the R6 and Ra’s smaller images so we examine the same area of each camera’s images. 

As with the R6, I also saw no “magic ISO” setting where the R5 performed better than at other settings. Noise increased in proportion to the ISO speed. The R5 proved perfectly usable up to ISO 3200, with ISO 6400 acceptable for stills when necessary. But I would not recommend the R5 for those who like to shoot Milky Way scenes at ISO 12,800. 

For nightscapes, a good practice that would allow using lower ISO speeds would be to shoot the sky images with a star tracker, then take separate long untracked exposures for the ground.

NOTE: In my testing I look first and foremost at actual real-world results. For those interested in more technical tests and charts, I refer you to DxOMark’s report on the Canon R5.  


NOISE PERFORMANCE — DEEP-SKY

This compares the R5 at the typical ISO settings used for deep-sky imaging, with no noise reduction applied to the raw files for this set. The inset shows the portion of the frame contained in the blow-ups.

Deep-sky imaging with a tracking mount is more demanding, due to its longer exposures of up to several minutes for each “sub-frame.” 

On a series of deep-sky exposures through a telescope, above, the R5 again showed quite usable images up to ISO 1600 and 3200, with ISO 6400 a little too noisy in my opinion unless a lot of noise reduction was applied or many images were shot to stack later.  

This compares the R5 to the R6 and Ra cameras at ISO 6400, higher than typically used for deep-sky imaging. No noise reduction was applied to the raw files.

As with the nightscape set, at high ISOs, such as at ISO 6400, the R5 did show more noise than the R6 and Ra, as well as more colour splotchiness in the dark sky, and lower contrast. The lower dynamic range of the R5’s smaller pixels is evident here. 

Just as with nightscapes, the lesson with the R5 is to keep the ISO low if at all possible. That means longer exposures with good auto-guiding, but that’s a best practice with any camera.

This compares the R5 to the R6 and Ra cameras at the lower ISOs of 800 and 1600 best for deep-sky imaging, for better dynamic range. No noise reduction was applied to the raw files. 

At lower ISOs that provide better dynamic range, shown above, the difference in noise levels between the three cameras was not that obvious. Each camera presented very similar images, with the R6 having a coarser noise than the Ra and R5. 

In all, I was surprised the R5 performed as well as it did for deep-sky imaging. See my comments below about its resolution advantage. 


ISO INVARIANCY

The flaw in many Canon DSLRs, one documented in my 2017 review of the 6D Mark II, was their poor dynamic range due to the lack of an ISO invariant sensor design. 

Canon R-series mirrorless cameras have largely addressed this weakness. As with the R and R6, the sensor in the R5 appears to be nicely ISO invariant. 

Where ISO invariancy shows itself to advantage is on nightscapes where the starlit foreground is often dark and underexposed. Bringing out detail in the shadows in raw files requires a lot of Shadow Recovery or increasing the Exposure slider. Images from an ISO invariant sensor can withstand the brightening “in post” far better, with minimal noise increase or degradations such as a loss of contrast, added banding, or horrible discolourations. 

This shows the same scene with the R5 progressively underexposed by shooting at a lower ISO then boosted in exposure in Adobe Camera Raw.

As I do for such tests, I shot sets of images at the same shutter speed, one well-exposed at a high ISO, then several at successively lower ISOs to underexpose by 1 to 4 stops. I then brightened the underexposed images by increasing the Exposure in Camera Raw by the same 1 to 4 stops. In an ideal ISO invariant sensor, all the images should look the same. 

The R5 performed well in images underexposed by up to 3 stops. Images underexposed by 4 stops started to fall apart with low contrast and a magenta cast. This was worse performance than the R6, which better withstood underexposure by as much as 4 stops, and fell apart at 5 stops of underexposure. 

While it can withstand underexposure, the lesson with the R5 is to still expose nightscapes as well as possible, likely requiring a separate longer exposure for the dark ground. Expose to the right! Don’t depend on being able to save the image by brightening “in post.” But again, that’s a best practice with any camera. 


THERMAL NOISE

Here I repeat some of the background information from my R6 review. But it bears repeating, as even skilled professional photographers often misunderstand the various forms of noise and how to mitigate them.

All cameras will exhibit thermal noise in long exposures, especially on warm nights. This form of heat-induced noise peppers the shadows with bright or “hot” pixels, often brightly coloured. 

This is not the same as the shot and read noise that adds graininess to high-ISO images and that noise reduction software can smooth out later in post. 

Thermal noise is more insidious and harder to eliminate in processing without harming the image. However, Monika Deviat offers a clever method here at her website

This shows a long-exposure nightscape scene both without and with Long Exposure Noise Reduction turned on. LENR eliminated most, though not all, of the hot pixels in the shadows. 

I found the R5 was prone to many hot pixels in long nightscape exposures where they show up in dark, underexposed shadows. I did not find a prevalence of hot pixels in well-exposed deep-sky images. 


LONG EXPOSURE NOISE REDUCTION

With all cameras a setting called Long Exposure Noise Reduction (LENR) eliminates this thermal noise by taking a “dark frame” and subtracting it in-camera to yield a raw file largely free of hot pixels, and other artifacts such as edge glows. 

The LENR option on the R5 did eliminate most hot pixels, though sometimes still left, or added, a few (or they might be cosmic ray hits). LENR is needed more on warm nights, and with longer exposures at higher ISOs. So the extent of thermal noise in any camera can vary a lot from shoot to shoot, and season to season.

This compares a long exposure of nothing (with the lens cap on), both without LENR (left) and with LENR (right), to show the extent of just the thermal noise.

The comparison above shows just thermal noise in long exposures with and without LENR, to show its effectiveness. However, bear in mind in this demo the raw files have been boosted a lot in exposure and contrast (using DxO PhotoLab with the settings shown) to exaggerate the visibility of the noise. 

Like the R6, when LENR is actively taking a dark frame, the R5’s rear screen indicates “Busy,” which is annoyingly bright at night, exactly when you would be employing LENR. To hide this display, the only option is to close the screen. Instead, the unobtrusive top LCD screen alone should be used to indicate a dark frame is in progress. It does with the Ra, though Busy also displays on its rear screen as well, which is unnecessary.

As with all mirrorless cameras, the R5 lacks the “dark frame buffer” present in Canon full frame DSLRs that allows several exposures to be taken in quick succession even with LENR on.

Long Exposure Noise Reduction is useful when the gap in time between exposures it produces is not critical.

With all Canon R cameras, turning on LENR forces the camera to take a dark frame after every light frame, doubling the time it takes to finish every exposure. That’s a price many photographers aren’t willing to pay, but on warm nights I find it can be essential, and a best practice, for the reward of cleaner images out of camera. I found it is certainly a good practice with the R5. 

TIP: If you find hot pixels are becoming more obvious over time, try this trick: turn on the Clean Manually routine for 30 seconds to a minute. In some cameras this can remap the hot pixels so the camera can better eliminate them. 


STAR QUALITY 

Using LENR with the R5 did not introduce any oddities such as oddly-coloured, green or wiped-out stars. Even without LENR I saw no evidence of green stars, a flaw that plagues some Sony cameras at all times, or Nikons when using LENR. 

This is a single developed raw frame from the stack of four minute exposures used to create the final image shown at the top. It shows sharp and nicely coloured stars, with no odd green stars. 

Canons have always been known for their good star colours, and the R5 maintains the tradition. According to DPReview the R5 has a mild low-pass anti-alias filter in front of its sensor. Cameras which lack such a sensor filter do produce sharper images, but stars that occupy only one or two pixels might not de-Bayer properly into the correct colours. I did not find that an issue with the R5.

As in the R6, I also saw no evidence of “star-eating,” a flaw Nikons and Sonys have been accused of over the years, due to aggressive in-camera noise reduction even on raw files. Canons have largely escaped charges of star-eating. 


RED SENSITIVITY 

The R5 I bought was a stock “off-the-shelf” model. It is Canon’s now-discontinued EOS Ra that was “filter-modified” to record a greater level of the deep-red wavelength from red nebulas in the Milky Way. As I show below, compared to the Ra, the R5 did well, but could not record the depth of nebulosity the Ra can, to be expected for a stock camera. 

However, bright nebulas will still be good targets for the R5. But if it’s faint nebulosity you are after, both in wide-field Milky Way images and telescopic close-ups, consider getting an R5 “spectrum modified” by a third-party supplier. Or modifying an EOS R.  

This compares identically processed four-minute exposures at ISO 800 with the R5 vs. the red-sensitive Ra. 

EDGE ARTIFACTS and EDGE GLOWS

DSLRs are prone to vignetting along the top and bottom of the frame from shadowing by the upraised mirror and mirror box. Not having a mirror, and a sensor not deeply recessed in the body, largely eliminates this edge vignetting in mirrorless cameras. 

While the Ra shows a very slight vignetting along the bottom of the frame (visible in the example above), the R5 was clean and fully illuminated to the edges, as it should be.

I was also pleased to see the R5 did not exhibit any annoying “amp glows” — dim, often magenta glows at the edge of the frame in long exposures, created by heat emitted from sensor electronics adding infrared (IR) glows to the image. 

I saw noticeable amp glows in the Canon R6 which could only be eliminated by taking LENR dark frames. It’s a flaw that has yet to be eliminated with firmware updates. Taking LENR darks is not required with the R5, except to reduce thermal hot pixels as noted above.

With a lack of IR amp glows, the R5 should work well when filter-modified to record either more visible Hydrogen-alpha red light, or deeper into the infrared spectrum. 


Resolution — Nightscapes 

Now we come to the very reason to get an R5, its high resolution. Is the difference visible in typical astrophotos? In a word, yes. If you look closely. 

If people only see your photos on Facebook or Instagram, no one will ever see any improvement in your images! But if your photos are seen as large prints, or you are simply a stickler for detail, then you will be happy with the R5’s 45 megapixels. (Indeed, you might wish to wait for the rumoured even higher megapixel Canon 5S!)

This compares identically processed four-minute exposures at ISO 800 with the R5 vs. the red-sensitive Ra. 

Nightscapes, and indeed all landscape photos by day or by night, is where you will see the benefit of more megapixels. Finer details in the foreground show up better. Images are less pixelated. In test images with all three cameras, the R5 did provide sharper images to be sure. But you do have to zoom in a lot to appreciate the improvement. 


Resolution — lunar imaging

This compares blow-ups of images of the Moon taken through a 5-inch f/6 refractor (780mm focal length) with the R6 and R5. 

The Moon through a telescope is another good test of resolution. The above comparison shows how the R5’s smaller 4.4-micron pixels do provide much sharper details and less pixelation than the R6. 

Of course, one could shoot at an even longer focal length to increase the “plate scale” with the R6. But at that same longer focal length the R5 will still provide better resolution, up to the point where its pixels are sampling more than what the atmospheric seeing conditions permit to be resolved. For lunar and planetary imaging, smaller pixels are always preferred, as they allow you to reach the seeing limit with shorter and often faster optical systems. 


Resolution — deep sky

This compares extreme blow-ups of images of the North America Nebula used for the other tests, shot with a 94mm f/4.5 refractor with the three cameras.

On starfields, the difference is not so marked. As I showed in my review of the R6, with “only” 20 megapixels the R6 can still provide detailed deep-sky images. 

However, in comparing the three cameras above, with images taken at a focal length of 420mm, the R5 does provide sharper stars, with faint stars better recorded, and with less blockiness (i.e. “square stars”) on all the star images. At that focal length the plate scale with the R5 is 2.1 arc seconds per pixel. With the R6 it is 3.2 arc seconds per pixel. 

This is dim green Comet PanSTARRS C/2017 K2, at top, passing above the star clusters IC 4756 at lower left and NGC 6633 at lower right on May 25-26, 2022. This is a stack of ten 5-minute exposures with a William Optics RedCat 51 at f/4.9 and the Canon R5 at ISO 800. 

The R5 is a good choice for shooting open and globular star clusters, or any small targets such as planetary nebulas, especially with shorter focal length telescopes. Bright targets will allow using lower ISOs, mitigating any of the R5’s extra noise. 

With an 800mm focal length telescope, the plate scale with the R5 will be 1.1 arc seconds per pixel, about the limit most seeing conditions will permit resolving. With even longer focal length telescopes, the R5’s small pixels would be oversampling the image, with little gain in resolution, at least for deep-sky subjects. Lunar and planetary imaging can benefit from plate scales of 0.5 arc seconds per pixel or smaller. 


CAN YOU CreatE resolution?

This compares an original R6 image with the same image rescaled 200% in ON1 Resize AI and Topaz Gigapixel AI, and with those three compared to an original R5 image. 

Now, one can argue that today’s AI-driven scaling programs such as ON1 Resize AI and Topaz Gigapixel AI can do a remarkable job up-sizing images while enhancing and sharpening details. Why buy a higher-megapixel camera when you can just sharpen images from a lower-resolution model? 

While these AI programs can work wonders on regular images, I’ve found their machine-learning seems to know little about stars, and can often create unwanted artifacts. 

In scaling up an R6 image by 200%, ON1 Resize AI 2022 made a mess of the stars and sky background. Topaz Gigapixel AI did a much better job, leaving few artifacts. But using it to double the R6 image in pixel count still produced an image that does not look as sharp as an original R5 image, despite the latter having fewer pixels than the upsized R6 image. 

Yes, we are definitely pixel-peeping! But I think this shows that it is better to have the pixels to begin with in the camera, and to not depend on software to generate sharpness and detail. 


VIDEO Resolution 

The R5’s 45-megapixel sensor also makes possible its headline selling point when it was released in 2020: 8K movie recording, with movies sized 8192 x 4320 (DCI standard) or 7680 x 4320 (UHD standard) at 29.97 frames per second, almost IMAX quality.

Where the R6’s major selling point for me was its low-light video capability, the R5’s 8K video prowess was less important. Or so I thought. With testing, I can see it will have its place in astrophotography, especially solar eclipses. 

The R5 offers the options of 8K and 4K movies each in either the wider DCI Digital Cinema standard (8K-D and 4K-D) or more common Ultra-High Definition standard (8K-U and 4K-U), as well as conventional 1080 HD.
This shows the Moon shot with the same 460mm-focal length telescope, with full-width frame grabs from movies shot in 8K, 4K, and 4K Movie Crop modes.

Unlike the original Canon R and Rp, the R5 and R6 can shoot 4K movies sampled from the full width of their sensors, so there is no crop factor in the field of view recorded with any lens. 

However, like the R6, the R5 also offers the option of a Movie Crop mode which samples a 4K movie from the central 4096 (4K-D) or 3840 (4K-U) pixels of the sensor. As I show above, this provides a “zoomed-in” image with no loss of resolution, useful when wide field of view is not so important as is zooming into small targets, such as for lunar and solar movies. 

This compares close-ups of frame grabs of the Moon movies shown in full-frame above, as well as a frame from an R6 movie, to compare resolutions.

So what format produces the best resolution when shooting movies? As I show above, magnified frame grabs of the Moon demonstrate that shooting at 8K provides a much less pixelated and sharper result than either the 4K-Fine HQ (which creates a “High-Quality” 4K movie downsampled from 8K) or a standard 4K movie. 

Shooting a 4K movie with the R6 also produced a similar result to the 4K movies from the R5. The slightly softer image in the R5’s 4K frame can, I think, be attributed more to atmospheric seeing. 


Solar eclipse use

Shooting the highest resolution movies of the Moon will be of prime interest to astrophotographers when the Moon happens to be passing in front of the Sun! 

That will happen along a narrow path that crosses North America on April 8, 2024. Capturing the rare total eclipse of the Sun in 8K video will be a goal of many. At the last total solar eclipse in North America, on August 21, 2017, I was able to shoot it in 4K by using a then state-of-the-art top-end Canon DSLR loaned to me by an IMAX movie production company! 

And who knows, by 2024 we might have 100-megapixel cameras capable of shooting and recording the firehose of data from 12K video! But for now, even 8K can be a challenge.

This compares the R5 at 8K with it in the best quality 4K Fine HQ vs. the R5 and R6 in their 4K Movie Crop modes.

However, do you need to shoot 8K to get sharp Moon, Sun or eclipse movies? The above shows the 8K frame-grab compared to the R5’s best quality full-frame 4K Fine, and the R5’s and R6’s 4K Movie Crop mode that doesn’t resample or bin pixels from the larger sensor to create a 4K movie. The Cropped movies look only slightly softer than the R5 at 8K, with less pixelation than the 4K Fine HQ movie. 

When shooting the Sun or Moon through a telescope or long telephoto lens, the wide field of a full-frame movie might not be required, even to take in the two- or three-degree-wide solar corona around the eclipsed Sun. 

However, if a wide field for the maximum extent of the outer corona, combined with sharp resolution is the goal, then a camera like the Canon R5 capable of shooting 8K movies will be the ticket. 

And 8K will be ideal for wide-angle movies of the passage of the Moon’s shadow during any eclipse, or for moderate fields showing the eclipsed Sun flanked by Jupiter and Venus on April 8, 2024.


Canon CLOG3

This shows the difference (using frame grabs from 4K movies) between shooting in Canon C-Log3 and shooting with normal “in-camera” colour grading. The exposures were the same. 

Like the R6, the R5 offers the option of shooting movies in Canon’s C-Log3 profile, which records internally in 10-bit, preserving more dynamic range in movies, up to 12 stops. The resulting movie looks flat, but when “colour graded” later in post, the movie records much more dynamic range, as I show above. Without C-Log3, the bright sunlit lunar crescent is blown out, as will be the Sun’s inner corona. 

The bright crescent Moon with dim Earthshine is a good practice-run stand-in for the eclipsed Sun with its wide range of brightness from the inner to the outer corona. 

Sample Moon Movies

For the full comparison of the R5 and R6 in my test shoot of the crescent Moon, see this narrated demo movie on Vimeo for the 4K movies, shot in various modes, both full-frame and cropped, with C-Log3 on and off. 

Keep in mind that video compression in the on-line version may make it hard to see the resolution difference between shooting modes. 

A “private link” 10-minute video on Vimeo demonstrating 4K video clips with the R5 and R6.

For a movie of the 8K footage, though downsized to 4K for the Vimeo version (the full sized 8K file was 29 Gigs!), see this sample movie below on Vimeo. 

A “private link” video on Vimeo demonstrating 8K video clips with the R5.


LOw-Light VIDEO 

Like the R6, the R5 can shoot at a dragged shutter speed as slow as 1/8-second. That slow shutter, combined with a fast f/1.4 to f/2 lens, and ISOs as high as 51,200 are the keys to shooting movies of the night sky. 

Especially auroras. Only when auroras get shadow-casting bright can we shoot at the normal 1/30-second shutter speed of movies and at lower ISOs. 

This compares frame grabs of aurora movies shot the same night with the R5 at 8K and 4K with the Canon R6 at 4K, all at ISO 51,200.

I was able to shoot a decent aurora one night from home with both the R5 and R6, and with the same fast TTArtisan 21mm f/1.5 RF lens. The sky and aurora changed in brightness from the time I shot with the R6 first to the R5 later. But even so, the movies serve as a look at how the two cameras perform for real-time aurora movies. 

Auroras are where we need to shoot full-frame, for the maximum field of view, and at high ISOs. The R5’s maximum ISO is 51,200, while the R6 goes up to 204,800, though it is largely unusable at that speed for actual shooting, just for previewing scenes.

As expected, the R6 was much less noisy than the R5, by about two stops. The R5 is barely usable at ISO 51,200, while the R6 works respectably well at that speed. If auroras get very bright, then slower ISOs can be used, making the R5 a possible camera for low-light use, but it would not be a first choice, unless 8K auroras are a must-have. 

 Sample aurora Movies

For a narrated movie comparing the R5 and R6 at 4K on the aurora, stepping both through a range of ISO speeds, see this movie at Vimeo.

A “private link” video on Vimeo demonstrating 4K aurora clips with the R5 and R6.

For a movie showing the same aurora shot with the R5 at 8K, see this movie. However, it has been down-sized to 4K for on-line viewing, so you’ll see little difference between it and the 4K footage. Shooting at 8K did not improve or smooth noise performance. 

A “private link” video on Vimeo demonstrating 8K aurora clips with the R5.


BATTERY LIFE — Stills and video

Canon’s new LP-E6NH battery supports charging through the USB-C port and has a higher 2130mAh capacity than the 1800mAh LP-E6 batteries. However, the R5 is compatible with the older batteries.

Like the R6, the R5 comes with a new version of Canon’s standard LP-E6 battery, the LP-E6NH. 

On mild nights, I found the R5 ran fine on one battery for the 3 to 4 hours needed to shoot a time-lapse sequence, or set of deep-sky images, with power to spare. Now, that was with the camera in “Airplane Mode,” which I always use regardless, to turn off the power-consuming WiFi and Bluetooth, which I never use on cameras.

As I noted with the R6, for demanding applications, especially in winter, the R5 can be powered by an outboard USB power bank that has Power Delivery or “PD” capability.

The exception for battery use is when shooting videos, especially 8K. That can drain a battery after an hour of recording, though it takes only 10 to 12 minutes of 8K footage to fill a 128 gigabyte card. While less than half that length will be needed to capture any upcoming total eclipse from diamond ring to diamond ring, the result is still a massive file.


OVERHEATING

More critically, the R5 is also infamous for overheating and shutting down when shooting 8K movies, after a time that depends on how hot the environment is. I found the R5 shot 8K or 4K Fine HQ for about 22 minutes at room temperature before the overheat warning first came on, then shut off recording two or three minutes later. Movie recording cannot continue until the R5 cools off sufficiently, which takes at least 10 to 15 minutes. 

That deficiency might befoul unwary eclipse photographers in 2024. The answer for “no-worry” 8K video recording is the Canon R5C, the video-centric version of the R5, with a built-in cooling fan. 


Features and usability

While certainly not designed with astrophotography in mind, the R5 has several hardware and firmware features that are astrophoto friendly. 

The R5’s Canon-standard flip screen

Like all Canon cameras made in the last few years, the R5 has Canon’s standard articulated screen, which can be angled up for convenient viewing when on a telescope. It is also a full touch screen, with all important camera settings and menus adjustable on screen, good for use at night. 

With 2.1 million dots, the R5’s rear screen has a higher resolution than the 1.62-million-dot screen of the R6, and much higher than the 1 million pixels of the Rp’s screen, but is the same resolution as in the R and Ra. 

The R5’s top-mounted backlit LCD screen

The R5, like the original R, has a top backlit LCD screen for display of current camera settings, battery level and Bulb timer. The lack of a top screen was one of my criticisms of the R6. 

Yes, the hardware Mode dial of the R6 and Rp does make it easier to switch shooting modes, such as quickly changing from Stills to Movie. However, for astrophotography the top screen provides useful information during long exposures, and is handy to check when the camera is on a telescope or tripod aimed up to the sky, without spoiling dark adaptation. I prefer to have one. 

The R5’s front-mounted N3-style remote port

The R5’s remote shutter port, used for connecting external intervalometers or time-lapse motion controllers, is Canon’s professional-grade three-pronged N3 connector. It’s sturdier than the 2.5mm mini-phono plug used by the Rp, R and R6. It’s a plus for the R5. 

As with all new cameras, the R5’s USB port is a USB-C type. A USB-C cable is included.

The R5’s back panel buttons and controls

Like the R6, the R5 has a dedicated magnification button on the back panel for zooming in when manually focusing or inspecting images. In the R and Ra, that button is only on the touch panel rear screen, where it has to be called up by paging to that screen, an inconvenience. While virtual buttons on a screen are easier to see and operate at night than physical buttons, I find a real Zoom button handy as it’s always there.

The R5’s twin cards, a CFexpress Type B and an SD UHS-II 

To handle the high data rates of 8K video and also 4K video when set to the high frame rate option of 120 fps, one of the R5’s memory card slots requires a CFexpress Type B card, a very fast but more costly format. 

As I had no card reader for this format, I had to download movies via a USB cable directly from the camera to my computer, using Canon’s EOS Utility software, as Adobe Downloader out of Adobe Bridge refused to do the job. Plan to buy a card reader.

Allocating memory card use

In the menus, you can choose to record video only to the CFexpress, and stills only to the SD card, or both stills and movies to each card for a backup, with the limitation that 8K and 4K 120fps won’t record to the SD card, even very fast ones. 


FIRMWARE FEATURES

Setting the Interval Timer

Unlike the Canon R and Ra (which both annoyingly lack a built-in intervalometer), but like the R6, the R5 has an Interval Timer in its firmware. This can be used to set up a time-lapse sequence, but with exposures only up to the maximum of 30 seconds allowed by the camera’s shutter speed settings, true of most in-camera intervalometers. Even so, this is a useful function for simple time-lapses.

Setting the Bulb Timer

As with most recent Canon DSLRs and DSLMs, the R5 also includes a built-in Bulb Timer. This allows setting an exposure of any length (many minutes or hours) when the camera is in Bulb mode. However, it cannot be combined with the Interval Timer for multiple exposures; it is good only for single shots. Nevertheless, I find it useful for shooting long exposures for the ground component of nightscape scenes. 

Custom button functions

While Canon cameras don’t have Custom Function buttons per se (unlike Sonys), the R5’s various buttons and dials can be custom programmed to functions other than their default assignments. I assign the * button to turning on and off the Focus Peaking display and, as shown, the AF Point button to a feature only available as a custom function, one that temporarily brightens the rear screen to full, good for quickly checking framing at night. 

Assigning Audio Memos to the Rate button

A handy feature of the R5 is the ability to add an audio notation to images. You shoot the image, play it back, then use the Rate button (if so assigned) to record a voice memo of up to 30 seconds, handy for making notes in the field about an image or a shoot. The audio notes are saved as WAV files with the same file number as the image. 

The infamous Release Shutter Without Lens command

Like other EOS R cameras, the R5 has this notorious “feature” that trips up every new user who attaches their Canon camera to a telescope or manual lens, only to find the shutter suddenly doesn’t work. The answer is to turn ON “Release Shutter w/o Lens” found buried under Custom Functions Menu 4. Problem solved! 

OTHER FEATURES

I provide more details of other features and settings of the R5, many of which are common to the R6, in my review of the R6 here

Multi-segment panoramas with the R5, like this aurora scene, yield superb resolution but can become massive in size, pressing the ability of software and hardware to process them. 

CONCLUSION

No question, the Canon R5 is costly. Most buyers would need to have very good daytime uses to justify its purchase, with astrophotography a secondary purpose. 

That said, other than low-light night sky videos, the R5 does work very well for all forms of astrophotography, providing a level of resolution that lesser cameras simply cannot. 

Nevertheless, if it is just deep-sky imaging that is of interest, then you might be better served with a dedicated cooled-sensor CMOS camera, such as one of the popular ZWO models, and the various accessories that need to accompany such a camera. 

But for me, when it came time to buy another premium camera, I still preferred to have a model that could be used easily, without computers, for many types of astro-images, particularly nightscapes, tracked wide-angle starfields, as well as telescopic images. 

Since buying the R5, after first suspecting it would prove too noisy to be practical, it has in fact become my most used camera, at least for all images where the enhanced red sensitivity of the EOS Ra is not required. But for low-light night videos, the R6 is the winner.

However, to make use of the R5’s resolution, you do have to match it with sharp, high-quality lenses and telescope optics, and have the computing power to handle its large files, especially when stitching or stacking lots of them. The R5 can be just the start of a costly spending spree! 

— Alan, June 23, 2022 / © 2022 Alan Dyer / AmazingSky.com  


Testing the Canon R6 for Astrophotography


In an extensive technical blog, I put the Canon R6 mirrorless camera through its paces for the demands of astrophotography. 

Every major camera manufacturer, with the lone exception of stalwart Pentax, has moved from producing digital lens reflex (DSLR) cameras, to digital single lens mirrorless (DSLM) cameras. The reflex mirror is gone, allowing for a more compact camera, better movie capabilities, and enhanced auto-focus functions, among other benefits. 

But what about for astrophotography? I reviewed the Sony a7III and Nikon Z6 mirrorless cameras here on my blog and, except for a couple of points, found them excellent for the demands of most astrophotography. 

For the last two years I’ve primarily used Canon’s astro-friendly and red-sensitive EOS Ra mirrorless, a model sadly discontinued in September 2021 after just two years on the market. I reviewed that camera in the April 2020 issue of Sky & Telescope magazine, with a quick first look here on my blog

The superb performance of the Ra has prompted me to stay with the Canon mirrorless R system for future camera purchases. Here I test the mid-priced R6, introduced in August 2020.

CLICK or TAP on an image to bring it up full screen for closer inspection. All images are © 2021 by Alan Dyer/AmazingSky.com. Use without permission is prohibited.

M31, the spiral galaxy in Andromeda, with the Canon R6 mirrorless camera. It is a stack of 8 x 8-minute exposures at ISO 800, blended with a stack of 8 x 2-minute exposures at ISO 400 for the core, to prevent it from overexposing too much, all with a SharpStar 76mm apo refractor at f/4.5 with its field flattener/reducer.

TL;DR SUMMARY

The Canon R6 has proven excellent for astrophotography, exhibiting better dynamic range and shadow recovery than most Canon DSLRs, due to the ISO invariant design of the R6 sensor. It is on par with the low-light performance of Nikon and Sony mirrorless cameras. 

The preview image is sensitive enough to allow easy framing and focusing at night. The movie mode produces usable quality up to ISO 51,200, making 4K movies of auroras possible. Canon DSLRs cannot do this. 

Marring the superb performance are annoying deficiencies in the design, and one flaw in the image quality – an amp glow – that particularly impacts deep-sky imaging.

R6 pros

The Canon R6 is superb for its:

  • Low noise, though not exceptionally so
  • ISO invariant sensor performance for good shadow recovery 
  • Sensitive live view display with ultra-high ISO boost in Movie mode 
  • Relatively low noise Movie mode with full frame 4K video
  • Low light auto focus and accurate manual focus assist  
  • Good battery life 

R6 cons

The Canon R6 is not so superb for its:

Design Deficiencies 

  • Lack of a top LCD screen
  • Bright timer display in Bulb on the rear screen
  • No battery level indication when shooting 
  • Low grade R3-style remote jack, same as on entry-level Canon DSLRs 

Image Quality Flaw

  • Magenta edge “amp glow” in long exposures 
The Canon Ra on the left with the 28-70mm f/2 RF lens and the Canon R6 on the right with the 70-200mm f/2/8 RF lens, two superb but costly zooms for the R system cameras.

CHOOSING THE R6

Canon’s first full-frame mirrorless camera, the 30-megapixel EOS R, was introduced in late 2018 to compete with Sony. As of late-2021 the main choices in a Canon DSLM for astrophotography are either the original R, the 20-megapixel R6, the 26-megapixel Rp, or the 45-megapixel R5. 

The new 24-megapixel Canon R3, while it has impressive low-noise performance, is designed primarily for high-speed sports and news photography. It is difficult to justify its $6,000 cost for astro work. 

I have not tested Canon’s entry-level, but full-frame Rp. While the Rp’s image quality is likely quite good, its small battery and short lifetime on a single charge will be limiting factors for astrophotography. 

Nor have I tested the higher-end R5. Friends who use the R5 for nightscape work love it, but with smaller pixels the R5 will be noisier than the R6, which lab tests at sites such as DPReview.com seem to confirm. 

Meanwhile, the original EOS R, while having excellent image quality and features, is surely destined for replacement in the near future – with a Canon EOS R Mark II? The R’s successor might be a great astrophoto camera, but with the Ra gone, I feel the R6 is currently the prime choice from Canon, especially for nightscapes.

I tested an R6 purchased in June 2021 and updated in August with firmware v1.4. I’ll go through its performance and functions with astrophotography in mind. I’ve ignored praised R6 features such as eye tracking autofocus, in-body image stabilization, and high speed burst rates. They are of limited or no value for astrophotography. 

Along the way, I also offer a selection of user tips, some of which are applicable to other cameras. 

LIVE VIEW FOCUSING AND FRAMING

“Back-of-the-camera” views of the R6 in its normal Live View mode (upper left) and its highly-sensitive Movie Mode (upper right), compared to views with four other cameras. Note the Milky Way visible with the R6 in its Movie mode, similar to the Sony in Bright Monitoring mode.

The first difference you will see when using any new mirrorless camera, compared to even a high-end DSLR, is how much brighter the “Live View” image is when shooting at night. DSLM cameras are always in Live View – even the eye-level viewfinder presents a digital image supplied by the sensor. 

As such, whether on the rear screen on in the viewfinder, you see an image that closely matches the photo you are about to take, because it is the image you are about to take. 

To a limit. DSLMs can do only so much to simulate what a long 30-second exposure will look like. But the R6, like many DSLMs, goes a long way in providing a preview image bright enough to frame a dark scene and focus on bright stars. Turn on Exposure Simulation to brighten the live image, and open the lens as wide as possible. 

The Canon R6 in its Movie Mode at ISO 204,800 and with a lens wide open.

But the R6 has a trick up its sleeve for framing nightscapes. Switch the Mode dial to Movie, and set the ISO up to 204,800 (or at night just dial in Auto ISO), and with the lens wide open and shutter on 1/8 second (as above), the preview image will brighten enough to show the Milky Way and dark foreground, albeit in a noisy image. But it’s just for aiming and framing.

This is similar to the excellent, but well-hidden Bright Monitoring mode on Sony Alphas. This high-ISO Movie mode makes it a pleasure using the R6 for nightscapes. The EOS R and Ra do not have this ability. While their live view screens are good, they are not as sensitive as the R6’s, with the R and Ra’s Movie modes able to go up to only ISO 12,800. The R5 can go up to “only” ISO 51,200 in its Movie mode, good but not quite high enough for live framing on dark nights. 

Comparing Manual vs. Auto Focus results with the R6.

The R6 will also autofocus down to a claimed EV -6.5, allowing it to focus in dim light for nightscapes, a feat impossible in most cameras. In practice with the Canon RF 15-35mm lens at f/2.8, I found the R6 can’t autofocus on the actual dark landscape, but it can autofocus on bright stars and planets (provided, of course, the camera is fitted with an autofocus lens). 

Autofocusing on bright stars proved very accurate. By comparison, while the Ra can autofocus on distant bright lights, it fails on bright stars or planets. 

Turning on Focus Peaking makes stars turn red, yellow or blue (your choice of colours) when they are in focus, as a reassuring confirmation. 

The Focus Peaking and Focus Guide menu.
The R6 live view display with Focus Guide arrows on and focused on a star, Antares.

In manual focus, an additional Focus Aid overlay provides arrows that close up and turn green when in focus on a bright star or planet. Or you can zoom in by 5x or 10x to focus by eye the old way by examining the star image. I wish the R6 had a 15x or 20x magnification; 5x and 10x have long been the Canon standards. Only the Ra offered 30x for ultra-precise focusing on stars. 

In all, the ease of framing and focusing will be the major improvement you’ll enjoy by moving to any mirrorless, especially if your old camera is a cropped-frame Canon Rebel or T3i! But the R6 particularly excels at ease of focusing and framing. 

NOISE PERFORMANCE

The key camera characteristic for astrophoto use is noise. I feel it is more important than resolution. There’s little point in having lots of fine detail if it is lost in a blizzard of high-ISO noise. And for astro work, we are almost always shooting at high ISOs.

Comparing the R6’s noise at increasingly higher ISO speeds on a starlit nightscape.

With just 20 megapixels, low by today’s standards, the R6 has individual pixels, or more correctly “photosites,” that are each 6.6 microns in size, the “pixel pitch.” 

By comparison, the 30-megapixel R (and Ra) has a pixel pitch of 5.4 microns, the 45-megapixel R5’s pixel pitch is 4.4 microns, while the acclaimed low-light champion in the camera world, the 12-megapixel Sony a7sIII, has large 8.5-micron photosites. 

The bigger the photosites (i.e. the larger the pixel pitch), the more photons each photosite can collect in a given amount of time – and the more photons they can collect, period, before they overfill and clip highlights. More photons equals more signal, and therefore a better signal-to-noise ratio, while the greater “full-well depth” yields higher dynamic range. 

Each generation of camera also improves the signal-to-noise ratio by suppressing noise via its sensor design and improved signal processing hardware and firmware. The R6 uses Canon’s latest DIGIC X processor shared by the company’s other mirrorless cameras. 

Comparing the R6 noise with the 6D MkII and EOS Ra on a deep-sky subject, galaxies.

In noise tests comparing the R6 against the Ra and Canon 6D Mark II, all three cameras showed a similar level of noise at ISO settings from 400 up to 12,800. But the 6D Mark II performed well only when properly exposed. Both the R6 and Ra performed much better for shadow recovery in underexposed scenes. 

Comparing the R6 noise with with the 6D MkII and EOS Ra on a shadowed nightscape.
Comparing the R6 noise with the EOS Ra on the Andromeda Galaxy at typical deep-sky ISO speeds.

In nightscapes and deep-sky images the R6 and Ra looked nearly identical at each of their ISO settings. This was surprising considering the Ra’s smaller photosites, which perhaps attests to the low noise of the astronomical “a” model. 

Or it could be that the R6 isn’t as low noise as it should be for a 20 megapixel camera. But it is as good as it gets for Canon cameras, and that’s very good indeed.

I saw no “magic ISO” setting where the R6 performed better than at other settings. Noise increased in proportion to the ISO speed. It proved perfectly usable up to ISO 6400, with ISO 12,800 acceptable for stills when necessary. 

ISO INVARIANCY

The flaw in many Canon DSLRs, one documented in my 2017 review of the 6D Mark II, was their poor dynamic range due to the lack of an ISO invariant sensor design. 

The R6, as with Canon’s other R-series cameras, has largely addressed this weakness. The sensor in the R6 appears to be nicely ISO invariant and performs as well as the Sony and Nikon cameras I have used and tested, models praised for their ISO invariant behaviour. 

Where this trait shows itself to advantage is on nightscapes where the starlit foreground is often dark and underexposed. Bringing out detail in the shadows in raw files requires a lot of Shadow Recovery or increasing the Exposure slider. Images from an ISO invariant sensor can withstand the brightening “in post” far better, with minimal noise increase or degradations such as a loss of contrast, added banding, or horrible discolourations. 

Comparing the R6 for ISO Invariancy on a starlit nightscape.

To test the R6, I shot sets of images at the same shutter speed, one well-exposed at a high ISO, then several at successively lower ISOs to underexpose by 1 to 5 stops. I then brightened the underexposed images by increasing the Exposure in Camera Raw by the same 1 to 5 stops. In an ideal ISO invariant sensor, all the images should look the same. 

The R6 did very well in images underexposed by up to 4 stops. Images underexposed by 5 stops started to fall apart, but I’ve seen that in Sony and Nikon images as well. 

Comparing the R6 for ISO Invariancy on a moonlit nightscape.

This behaviour applies to images underexposed by using lower ISOs than what a “normal” exposure might require. Underexposing with lower ISOs can help maintain dynamic range and avoid highlight clipping. But with nightscapes, foregrounds can often be too dark even when shot at an ISO high enough to be suitable for the sky. Foregrounds are almost always underexposed, so good shadow recovery is essential for nightscapes, and especially time-lapses, when blending in separate longer exposures for the ground is not practical.

With its improved ISO invariant sensor, the R6 will be a fine camera for nightscape and time-lapse use, which was not true of the 6D Mark II. 

For those interested in more technical tests and charts, I refer you to DxOMark’s report on the Canon R6.  

Comparing R6 images underexposed in 1-stop increments by using shorter shutter speeds.
Comparing R6 images underexposed in 1-stop increments by using smaller apertures.

However, to be clear, ISO invariant behaviour doesn’t help you as much if you underexpose by using too short a shutter speed or too small a lens aperture. I tested the R6 in series of images underexposed by keeping ISO the same but decreasing the shutter speed then the aperture in one-stop increments. 

The underexposed images fell apart in quality much sooner, when underexposed more than 3 stops. Again, this is behaviour similar to what I’ve seen in Sonys and Nikons. For the best image quality I feel it is always a best practice to expose well at the camera. Don’t count on saving images in post. 

An in-camera image fairly well exposed with an ETTR histogram.

TIP: Underexposing by using too short an exposure time is the major mistake astrophotographers make, who then wonder why their images are riddled with odd artifacts and patten noise. Always Expose to the Right (ETTR), even with ISO invariant cameras. The best way to avoid noise is to give your sensor more signal, by using longer exposures or wider apertures. Use settings that push the histogram to the right. 

LONG EXPOSURE NOISE REDUCTION

All cameras will exhibit thermal noise in long exposures, especially on warm nights. This form of noise peppers the shadows with hot pixels, often brightly coloured. 

This is not the same as the shot and read noise that adds graininess to high-ISO images and that noise reduction software can smooth out. This is a common misunderstanding, even among professional photographers who should know better! 

Thermal noise is more insidious and harder to eliminate in post without harming the image. However, Monika Deviat offers a clever method here at her website

The standard Canon LENR menu.

Long Exposure Noise Reduction (LENR) eliminates this thermal noise by taking a “dark frame” and subtracting it in-camera to yield a raw file free of hot pixels. 

And yes, LENR does apply to raw files, another fact even many professional photographers don’t realize. It is High ISO Noise Reduction that applies only to JPGs, along with Color Space and Picture Styles.

Comparing a dark nightscape without and with LENR on a warm night. Hot pixels are mostly gone at right.

The LENR option on the R6 did eliminate most hot pixels, though sometimes still left, or added, a few. LENR is needed more on warm nights, and with longer exposures at higher ISOs. So the extent of thermal noise in any camera can vary a lot from shoot to shoot.

When LENR is active, the R6’s rear screen lights up with “Busy,” which is annoyingly bright. To hide this display, the only option is to close the screen. 

As with the EOS Ra, and all mirrorless cameras, the R6 has no “dark frame buffer” that allows several exposures to be taken in quick succession even with LENR on. Canon’s full-frame DSLRs have this little-known buffer that allows 3, 4, or 5 “light frames” to be taken in a row before the LENR dark frame kicks in a locks up the camera on Busy. 

Comparing long exposure images with the lens cap on (dark frames), to show just thermal noise. The right edge of the frame is shown, blown up, to reveal the amp glow, which LENR removes.

With all Canon R cameras, and most other DSLRs, turning on LENR forces the camera to take a dark frame after every light frame, doubling the time it takes to finish every exposure. That’s a price many photographers aren’t willing to pay, but on warm nights it can be necessary, and a best practice, for the reward of cleaner images.

The standard Canon Sensor Cleaning menu.

TIP: If you find hot pixels are becoming more obvious over time, try this trick: turn on the Clean Manually routine for 30 seconds to a minute. In some cameras this can remap the hot pixels so the camera can better eliminate them.  

STAR QUALITY 

Using LENR with the R6 did not introduce any oddities such as oddly-coloured, green or wiped-out stars. Even without LENR I saw no evidence of green stars, a flaw that plagues some Sony cameras at all times, or Nikons when using LENR. 

Comparing the R6 for noise and star colours at typical deep-sky ISOs and exposure times.

Canons have always been known for their good star colours, and the R6 is no exception. According to DPReview the R6 has a low-pass anti-alias filter in front of its sensor. Cameras which lack such a sensor filter do produce sharper images, but stars that occupy only one or two pixels might not de-Bayer properly into the correct colours. That’s not an issue with the R6.

I also saw no “star-eating,” a flaw Nikons and Sonys have been accused of over the years, due to aggressive in-camera noise reduction even on raw files. Canons have always escaped charges of star-eating. 

VIGNETTING/SHADOWING

DSLRs are prone to vignetting along the top and bottom of the frame from shadowing by the upraised mirror and mirror box. Not having a mirror, and a sensor not deeply recessed in the body, largely eliminates this edge vignetting in mirrorless cameras. 

This illustrates the lack of edge shadows but magenta edge glows in a single Raw file boosted for contrast.

That is certainly true of the R6. Images boosted a lot in contrast, as we do with deep-sky photos, show not the slightest trace of vignetting along the top or bottom edges There were no odd clips or metal bits intruding into the light path, unlike in the Sony a7III I tested in 2018. 

The full frame of the R6 can be used without need for cropping or ad hoc edge brightening in post. Except …

EDGE ARTIFACTS/AMP GLOWS

The R6 did exhibit one serious and annoying flaw in long-exposure high-ISO images – a magenta glow along the edges, especially the right edge and lower right corner. 

Comparing a close-up of a nightscape, without and with LENR, to show the edge glow gone with LENR on.

Whether this is the true cause or not, it looks like “amplifier glow,” an effect caused by heat from circuitry illuminating the sensor with infra-red light. It shows itself when images are boosted in contrast and brightness in processing. It’s the sort of flaw revealed only when testing for the demands of astrophotography. It was present in images I took through a telescope, so it is not IR leakage from an auto-focus lens. 

I saw this type of amp glow with the Sony a7III, a flaw eventually eliminated in a firmware update that, I presume, turned off unneeded electronics in long exposures. 

Amp glow is something I have not seen in Canon cameras for many years. In a premium camera like the R6 it should not be there. Period. Canon needs to fix this with a firmware update.

UPDATE AUGUST 1, 2022: As of v1.6 of the R6 firmware, released in July 2022, the amp glow issue remains and has not been fixed. It may never be at this point.

It is the R6’s only serious image flaw, but it’s surprising to see it at all. Turning on LENR eliminates the amp glow, as it should, but using LENR is not always practical, such as in time-lapses and star trails.

For deep-sky photography high-ISO images are pushed to extremes of contrast, revealing any non-uniform illumination or colour. The usual practice of taking and applying calibration dark frames should also eliminate the amp glow. But I’d rather it not be there in the first place!

RED SENSITIVITY

The R6 I bought was a stock “off-the-shelf” model. It is Canon’s now-discontinued EOS Ra model that is (or was) “filter-modified” to record a greater level of the deep red wavelength from red nebulas in the Milky Way. Compared to the Ra, the R6 did well, but could not record the depth of nebulosity the Ra can, to be expected for a stock camera. 

Comparing the stock R6 with the filter-modified Ra on Cygnus nebulosity.

In wide-field images of the Milky Way, the R6 picked up a respectable level of red nebulosity, especially when shooting through a broadband light pollution reduction filter, and with careful processing. 

Comparing the stock R6 with the filter-modified Ra on the Swan Nebula with a telescope with minimal processing to the Raw images.
Comparing the stock R6 with the filter-modified Ra on the Swan Nebula with a telescope with a dual narrowband filter and with colour correction applied to the single Raw images.

However, when going after faint nebulas through a telescope, even the use of a narrowband filter did not help bring out the target. Indeed, attempting to correct the extreme colour shift introduced by such a filter resulted in a muddy mess and accentuated edge glows with the R6, but worked well with the Ra. 

While the R6 could be modified by a third party, the edge amp glow might spoil images, as a filter modification can make a sensor even more sensitive to IR light, potentially flooding the image with unwanted glows. 

TIP: Buying a used Canon Ra (if you can find one) might be one choice for a filter-modified mirrorless camera, one much cheaper than a full frame cooled CMOS camera such as a ZWO ASI2400MC. Or Spencer’s Camera sells modified versions of all the R series cameras with a choice of sensor filters. But I have not used any of their modded cameras.

RESOLUTION 

A concern of prospective buyers is whether the R6’s relatively low 20-megapixel sensor will be sharp enough for their purposes. R6 images are 5472 by 3648 pixels, much less than the 8000+ pixel-wide images from high-resolution cameras like the Canon R5, Nikon Z7II or Sony a1.

Unless you sell your astrophotos as very large prints, I’d say don’t worry. In comparisons with the 30-megapixel Ra I found it difficult to see a difference in resolution between the two cameras. Stars were nearly as well resolved in the R6, and only under the highest pixel-peeping magnification did stars look a bit more pixelated in the R6 than in the Ra. Faint stars were equally well recorded. 

Comparing resolution of the R6 vs. Ra with a blow-up of wide-field 85mm images
Comparing resolution of the R6 vs. Ra on blow-ups of the Andromeda Galaxy with a 76mm apo refractor. The R6 is more pixellated but it takes pixel peeping to see it!

The difference between 20 and 30 megapixels is not as great as you might think for arc-second-per-pixel plate scale. I think it would take going to the R5 with its 45 megapixel sensor to provide enough of a difference in resolution over the R6 to be obvious in nightscape scenes, or when shooting small, detailed deep-sky subjects such as globular clusters. 

If landscape or wildlife photography by day is your passion, with astrophotography a secondary purpose, then the more costly but highly regarded R5 might be the better choice. 

Super Resolution menu in Adobe Lightroom.

TIP: Adobe now offers (in Lightroom and in Camera Raw) a Super Resolution option, that users might think (judging by the rave reviews on-line) would be the answer to adding resolution to astro images from “low-res” cameras like the R6. 

Comparing a normal R6 image with the same image upscaled with Super Resolution.

Sorry! In my tests on astrophotos I’ve found Super Resolution results unsatisfactory. Yes, stars were less pixelated, but they became oddly coloured in the AI-driven up-scaling. Green stars appeared! The sky background also became mottled and uneven. 

I would not count on such “smart upscaling” options to add more pixels to astro-images from the R6. Then again, I don’t think there’s a need to. 

RAW vs. cRAW

Canon now offers the option of shooting either RAW or cRAW files, the latter being the same megapixel count but compressed in file size by almost a factor of two. This allows shooting twice as many images before card space runs out, perhaps useful for shooting lots of time-lapses on extended trips away from a computer. 

The R6 Image Quality menu with the cRAW Option.
Comparing an R6 cRAW with a RAW image.

However, the compression is not lossless. In high-ISO test images purposely underexposed, then brightened in post, I could see a slight degradation in cRAW images – the noise background looked less uniform and exhibited a blocky look, like JPG artifacts. 

The R6’s dual SD card slots.

TIP: With two SD card slots in the R6 (the second card can be set to record either a backup of images on card one, or serve as an overflow card) and the economy of large SD cards, there’s not the need to conserve card space as there once was. I would suggest always shooting in the full RAW format. Why accept any compression and loss of image quality? 

BATTERY LIFE

The R6 uses a new version of Canon’s standard LP-E6 battery, the LP-E6NH, that supports charging through the USB-C port and has a higher 2130mAh capacity than the 1800mAh LP-E6 batteries. However, the R6 is compatible with older batteries.

On warm nights, I found the R6 ran fine on one battery for the 3 to 4 hours needed to shoot a time-lapse sequence, with power to spare. However, as noted below, the lack of a top LCD screen means there’s no ongoing display of battery level, a deficiency for time-lapse and deep-sky work. 

For demanding applications, especially in winter, the R6 can be powered by an outboard USB power bank that has “Power Delivery” capability. That’s a handy feature. There’s no need to install a dummy battery leading out to a specialized power source. 

The R6’s Connection menu with Airplane mode to turn off battery-eating WiFi and Bluetooth.

TIP: Putting the camera into Airplane mode (to turn off WiFi and Bluetooth), turning off the viewfinder, and either switching off or closing the rear screen all helps conserve power. The R6 does not have GPS built in. Tagging images with location data requires connecting to your phone.

VIDEO USE

A major selling point for me was the R6’s low-light video capability. It replaces my Sony A7III, which had been my “go to” camera for real-time 4K movies of auroras. 

As best I can tell (from the dimmer auroras I’ve shot to date), the R6 performs equally as well as the Sony. It is able to record good quality (i.e. acceptably noise-free) 4K movies at ISO 25,600 to ISO 51,200. While it can shoot at up to ISO 204,800, the excessive noise makes the top ISO an emergency-use only setting. 

The R6’s Movie size and quality options, with 4K and Full HD formats and frame rates.
Comparing the R6 on a dim aurora at various high ISO speeds. Narrated at the camera — excuse the wind noise! Switch to HD mode for the best video playback quality. This was shot in 4K but WordPress plays back only in HD.

The R6 can shoot at a dragged shutter speed as slow as 1/8-second – good, though not as slow as the Sony’s 1/4-second slowest shutter speed in movie mode. That 1/8-second shutter speed and a fast f/1.4 to f/2 lens are the keys to shooting movies of the night sky. Only when auroras get shadow-casting bright can we shoot at the normal 1/30-second shutter speed and at lower ISOs.

As with Nikons (but not Sonys), the Canon R6 saves its movie settings separately from its still settings. When switching to Movie mode you don’t have to re-adjust the ISO, for example, to set it higher than it might have been for stills, very handy for taking both stills and movies of an active aurora, where quick switching is often required. 

Unlike the R and Rp, the R6 captures 4K movies from the full width of the sensor, preserving the field of view of wide-angle lenses. This is excellent for aurora shooting. 

The R6’s Movie Cropping menu option
A 4K movie of the Moon in full-frame and copped-frame modes, narrated at the camera. Again, this was shot in 4K but WordPress plays back only in HD.
Comparing blow-ups of frame-grabbed stills from a full-frame 4K vs. Cropped frame 4K. The latter is less pixellated.

However, the R6 offers the option of a “Movie Crop” mode. Rather than taking the 4K movie downsampled from the entire sensor, this crop mode records from a central 1:1 sampled area of the sensor. That mode can be useful for high-magnification lunar and planetary imaging, for ensuring no loss of resolution. It worked well, producing videos with less pixelated fine details in test movies of the Moon. 

Though of course I have yet to test it on one, the R6 should be excellent for movies of total solar eclipses. It can shoot 4K up to 60 frames per second in both full frame and cropped frame. It cannot shoot 6K (buy the R3!) or 8K (buy the R5!). 

The R6’s Canon Log settings menu for video files.

Shooting in the R6’s Canon cLog3 profile records internally in 10-bit, preserving more dynamic range in movies, up to 12 stops. During eclipses, that will be a benefit for recording totality, with the vast range of brightness in the Sun’s corona. It should also aid in shooting auroras which can vary over a huge range in brightness. 

Grading a cLog format movie in Final Cut under Camera LUT.

TIP: Processing cLog movies, which look flat out of camera, requires applying a cLog3 Look Up Table, or LUT, to the movie clips in editing, a step called “colour grading.” This is available from Canon, from third-party vendors or, as it was with my copy of Final Cut Pro, might be already installed in your video editing software. When shooting, turn on View Assist so the preview looks close to what the final graded movie will look like.

EXPOSURE TRACKING IN TIME-LAPSES

In one test, I shot a time-lapse from twilight to darkness with the R6 in Aperture Priority auto-exposure mode, of a fading display of noctilucent clouds. I just let the camera lengthen the shutter speed on its own. It tracked the darkening sky very well, right down to the camera’s maximum exposure time of 30 seconds, using a fish-eye lens at f/2.8. This demonstrated that the light meter in the R6 was sensitive enough to work well in dim light.

Other cameras I have used cannot do this. The meter fails at some point and the exposure stalls at 5 or 6 seconds long, resulting in most frames after that being underexposed. By contrast, the R6 showed excellent performance, negating the need for special bulb ramping intervalometers for some “holy grail” scenes. Here’s the resulting movie.

A time-lapse of 450 frames from 0.4 seconds to 30 seconds, with the R6 in Av mode. Set to 1080P for the best view!
A screenshot from LRTimelapse showing the smoothness of the exposure tracking (the blue line) through the sequence,

In addition, the R6’s exposure meter tracked the darkening sky superbly, with nary a flicker or variation. Again, few cameras can do this. Nikons have an Exposure Smoothing option in their Interval Timers which works well.

The R6 has no such option but doesn’t seem to need it. The exposure did fail at the very end, when the shutter reached its maximum of 30 seconds. If I had the camera on Auto ISO, it might have started to ramp up the ISO to compensate, a test I have yet to try. Even so, this is impressive time-lapse performance in auto-exposure.

MISSING FEATURES

The R6, like the low-end Rp, lacks a top LCD screen for display of camera settings and battery level. In its place we get a traditional Mode dial, which some daytime photographers will prefer. But for astrophotography, a backlit top LCD screen provides useful information during long exposures. 

The R6 top and back of camera view.

Without it, the R6 provides no indication of battery level while a shoot is in progress, for example, during a time-lapse. A top screen is also useful for checking ISO and other settings by looking down at the camera, as is usually the case when it’s on a tripod or telescope. 

The lack of a top screen is an inconvenience for astrophotography. We are forced to rely on looking at the brighter rear screen for all information. It is a flip-out screen, so can be angled up for convenient viewing on a telescope.

The R6’s flip screen, similar to most other new Canon cameras.

The R6 has a remote shutter port for an external intervalometer, or control via a time-lapse motion controller. That’s good! 

However, the port is Canon’s low-grade 2.5mm jack. It works, and is a standard connector, but is not as sturdy as the three-pronged N3-style jack used on Canon’s 5D and 6D DSLRs, and on the R3 and R5. Considering the cost of the R6, I would have expected a better, more durable port. The On/Off switch also seems a bit flimsy and easily breakable under hard use. 

The R6’s side ports, including the remote shutter/intervalometer port.

These deficiencies provide the impression of Canon unnecessarily “cheaping out” on the R6. You can forgive them with the Rp, but not with a semi-professional camera like the R6.

INTERVAL TIMER

Unlike the Canon R and Ra (which still mysteriously lack a built-in interval timer, despite firmware updates), the R6 has one in its firmware. Hurray! This can be used to set up a time-lapse sequence, but on exposures only up to the maximum of 30 seconds allowed by the camera’s shutter speed settings, true of most in-camera intervalometers. 

The Interval Timer menu page.

For 30-second exposures taken in succession as quickly as possible the interval on the R6 has to be set to 34 seconds. The reason is that the 30-second exposure is actually 32 seconds, true of all cameras. With the R6, having a minimum gap in time between shots requires an Interval not of 33 seconds as with some cameras, but 34 seconds. Until you realize this, setting the intervalometer correctly can be confusing. 

Like all Canon cameras, the R6 can be set to take only up to 99 frames, not 999. That seems a dumb deficiency. Almost all time-lapse sequences require at least 200 to 300 frames. What could it possibly take in the firmware to add an extra digit to the menu box? It’s there at in the Time-lapse Movie function that assembles a movie in camera, but not here where the camera shoots and saves individual frames. It’s another example where you just can’t fathom Canon’s software decisions.

Setting the Interval Timer for rapid sequence shots with a 30-second exposure.

TIP: If you want to shoot 100 or more frames, set the Number of Frames to 00, so it will shoot until you tell the camera to stop. But awkwardly, Canon says the way to stop an interval shoot is to turn off the camera! That’s crude, as doing so can force you to refocus if you are using a Canon RF lens. Switching the Mode dial to Bulb will stop an interval shoot, an undocumented feature. 

BULB TIMER

As with most recent Canon DSLRs and DSLMs, the menu also includes a Bulb Timer. This allows setting an exposure of any length (many minutes or hours) when the camera is in Bulb mode. This is handy for single long shots at night. 

The Bulb Timer menu page. Bulb Timer only becomes an active choice when the camera is on Bulb.

However, it cannot be used in conjunction with the Interval Timer to program a series of multi-minute exposures, a pity. Instead, a separate outboard intervalometer has to be used for taking an automatic set of any exposures longer than 30 seconds, true of all Canons. 

In Bulb and Bulb Timer mode, the R6’s rear screen lights up with a bright Timer readout. While the information is useful, the display is too bright at night and cannot be dimmed, nor turned red for night use, exactly when you are likely to use Bulb. The power-saving Eco mode has no effect on this display, precisely when you would want it to dim or turn off displays to prolong battery life, another odd deficiency in Canon’s firmware. 

The Bulb Timer screen active during a Bulb exposure. At night it is bright!

The Timer display can only be turned off by closing the flip-out screen, but now the viewfinder activates with the same display. Either way, a display is on draining power during long exposures. And the Timer readout lacks any indication of battery level, a vital piece of information during long shoots. The Canon R, R3 and R5, with their top LCD screens, do not have this annoying “feature.” 

TIP: End a Bulb Timer shoot prematurely by hitting the Shutter button. That feature is documented. 

IN-CAMERA IMAGE STACKING

The R6 offers a menu option present on many recent Canon cameras: Multiple Exposure. The camera can take and internally stack up to 9 images, stacking them by using either Average (best for reducing noise) or Bright mode (best for star trails). An Additive mode also works for star trails, but stacking 9 images requires reducing the exposure of each image by 3 stops, say from ISO 1600 to ISO 200, as I did in the example below. 

The Multiple Exposure menu page.

The result of the internal stacking is a raw file, with the option of also saving the component raws. While the options work very well, in all the cameras I’ve owned that offer such functions, I’ve never used them. I prefer to do any stacking needed later at the computer. 

Comparing a single image with a stack of 9 exposures with 3 in-camera stacking methods.

TIP: The in-camera image stacking options are good for beginners wanting to get advanced stacking results with a minimum of processing fuss later. Use Average to stack ground images for smoother noise. Use Bright for stacking sky images for star trails. Activate one of those modes, then control the camera with a separate intervalometer to automatically shoot and internally stack several multi-minute exposures. 

SHUTTER OPERATION

Being a mirrorless camera, there is no reflex mirror to introduce vibration, and so no need for a mirror lockup function. The shutter can operate purely mechanically, with physical metal curtains opening and closing to start and end the exposure. 

However, the default “out of the box” setting is Electronic First Curtain, where the actual exposure, even when on Bulb, is initiated electronically, but ended by the mechanical shutter. That’s good for reducing vibration, perhaps when shooting the Moon or planets through a telescope at high magnification. 

R6 Shutter Mode options.

In Mechanical, the physical curtains both start and end the exposure. It’s the mode I usually prefer, as I like to hear the reassuring click of the shutter opening. I’ve never found shutter vibration a problem when shooting deep sky images on a telescope mount of any quality. 

In Mechanical mode the shutter can fire at up to 12 frames a second, or up to 20 frames a second in Electronic mode where both the start and end of the exposure happen without the mechanical shutter. That makes for very quiet operation, good for weddings and golf tournaments! 

Electronic Shutter Mode is for fastest burst rates but has limitations.

Being vibration free, Electronic shutter might be great during total solar eclipses for rapid-fire bursts at second and third contacts when shooting through telescopes. Maximum exposure time is 1/2 second in this mode, more than long enough for capturing fleeting diamond rings.

Longer exposures needed for the corona will require Mechanical or Electronic First Curtain shutter. Combinations of shutter modes, drive rates (single or continuous), and exposure bracketing can all be programmed into the three Custom Function settings (C1, C2 and C3) on the Mode dial, for quick switching at an eclipse. It might not be until April 8, 2024 until I have a chance to test these features. And by then the R6 Mark II will be out! 

TIP: While the R6’s manual doesn’t state it, some reviews mention (including at DPReview) that when the shutter is in fully Electronic mode the R6’s image quality drops from 14-bit to 12-bit, true of most other mirrorless cameras. This reduces dynamic range. I would suggest not using Electronic shutter for most astrophotography, even for exposures under 1/2 second. For longer exposures, it’s a moot point as it cannot be used. 

The menu option that fouls up all astrophotographers using an R-series camera.

TIP: The R6 has the same odd menu item that befuddles many a new R-series owner, found on Camera Settings: Page 4. “Release Shutter w/o Lens” defaults to OFF, which means the camera will not work if it is attached to a manual lens or telescope it cannot connect to electronically. Turn it ON and all will be solved. This is a troublesome menu option that Canon should eliminate or default to ON. 

OTHER MENU FEATURES

The rear screen is fully touch sensitive, allowing all settings to be changed on-screen if desired, as well as by scrolling with the joystick and scroll wheels. I find going back to an older camera without a touchscreen annoying – I keep tapping the screen expecting it to do something! 

The Multi-Function Button brings up an array of 5 settings to adjust. This is ISO.

The little Multi-Function (M-Fn) button is a worth getting used to, as it allows quick access to a choice of five important functions such as ISO, drive mode and exposure compensation. However, the ISO, aperture and shutter speed are all changeable by the three scroll wheels. 

The Q button brings up the Quick Menu for displaying and adjusting key functions.

There’s also the Quick menu activated by the Q button. While the content of the Quick menu screen can’t be edited, it does contain a good array of useful functions, adjustable with a few taps. 

Under Custom settings, the Dials and Buttons can be re-assigned to other functions.

Unlike Sonys, the R6 has no dedicated Custom buttons per se. However, it does offer a good degree of customization of its buttons, by allowing users to re-assign them to other functions they might find more useful than the defaults. For example ….

This shows the AF Point button being re-assigned to the Maximize Screen Brightness (Temporary) command.
  • I’ve taken the AF Point button and assigned it to the Maximize Screen Brightness function, to temporarily boost the rear screen to full brightness for ease of framing. 
  • The AE Lock button I assigned to switch the Focus Peaking indicators on and off, to aid manual focusing when needed. 
  • The Depth of Field Preview button I assigned to switching between the rear screen and viewfinder, through that switch does happen automatically as you put your eye to the viewfinder.
  • The Set button I assigned to turning off the Rear Display, though that doesn’t have any effect when the Bulb Timer readout is running, a nuisance. 

While the physical buttons are not illuminated, having a touch screen makes it less necessary to access buttons in the dark. It’s a pity the conveniently positioned but mostly unused Rate button can’t be re-programmed to more useful functions. It’s a waste of a button. 

Set up the Screen Info as you like it by turning on and off screen pages and deciding what each should show.

TIP: The shooting screens, accessed by the Info button (one you do need to find in the dark!), can be customized to show a little, a lot, or no information, as you prefer. Take the time to set them up to show just the information you need over a minimum of screen pages. 

LENS AND FILTER COMPATIBILITY

The new wider RF mount accepts only Canon and third-party RF lenses. However, all Canon and third-party EF mount lenses (those made for DSLRs) will fit on RF-mount bodies with the aid of the $100 Canon EF-to-RF lens adapter. 

The Canon ER-to-RF lens adapter will be needed to attach R cameras to most telescope camera adapters and Canon T-rings made for older DSLR cameras.

This adapter will be necessary to attach any Canon R camera to a telescope equipped with a standard Canon T-ring. That’s especially true for telescopes with field flatterers where maintaining the standard 55mm distance between the flattener and sensor is critical for optimum optical performance. 

The shallower “flange distance” between lens and sensor in all mirrorless cameras means an additional adapter is needed not just for the mechanical connection to the new style of lens mount, but also for the correct scope-to-sensor spacing. 

The extra spacing provided by a mirrorless camera has the benefit of allowing a filter drawer to be inserted into the light path. Canon offers a $300 lens adapter with slide-in filters, though the choice of filters useful for astronomy that fit Canon’s adapter is limited. AstroHutech offers a few IDAS nebula filters.

Clip-in filters made for the EOS R, such as those offered by Astronomik, will also fit the R6. Though, again, most narrowband filters will not work well with an unmodified camera.

The AstroHutech adapter allows inserting filters into the light path on telescopes.

TIP: Alternatively, AstroHutech also offers its own lens adapter/filter drawer that goes from a Canon EF mount to the RF mount, and accepts standard 52mm or 48mm filters. It is a great way to add interchangeable filters to any telescope when using an R-series camera, while maintaining the correct back-focus spacing. I use an AstroHutech drawer with my Ra, where the modified camera works very well with narrowband filters. Using such filters with a stock R6 won’t be as worthwhile, as I showed above. 

A trio of Canon RF zooms — all superb but quite costly.

As of this writing, the selection of third-party lenses for the Canon RF mount is limited, as neither Canon or Nikon have “opened up” their system to other lens makers, unlike Sony with their E-mount system. For example, we have yet to see much-anticipated RF-mount lenses from Sigma, Tamron and Tokina. 

A trio of third party RF lenses — L to R: the TTArtisan 7.5mm f/2 and 11mm f/2.8 fish-eyes and the Samyang/Rokinon AF 85mm f/1.4.

Samyang offers 14mm and 85mm auto-focus RF lenses, but now only under their Rokinon branding. I tested the Samyang RF 85mm f/1.4 here at AstroGearToday

The few third-party lenses that are available, from TTArtisan, Venus Optics and other boutique Chinese lens companies, are usually manual focus lenses with reverse-engineered RF mounts offering no electrical contact with the camera. Some of these wide-angle lenses are quite good and affordable. (I tested the TTArtisan 11mm fish-eye here.)

Until other lens makers are “allowed in,” if you want lenses with auto-focus and camera metadata connections, you almost have to buy Canon. Their RF lenses are superb, surpassing the quality of their older EF-mount equivalents. But they are costly. I sold off a lot of my older lenses and cameras to help pay for the new Canon glass! 

I also have reviews of the superb Canon RF 15-35mm f/2.8, as well as the unique Canon RF 28-70mm f/2 and popular Canon RF 70-200mm f/2.8 lenses (a trio making up the  “holy trinity” of zooms) at AstroGearToday.com.

CONTROL COMPATIBILITY 

Astrophotographers often like to operate their cameras at the telescope using computers running specialized control software. I tested the R6 with two popular Windows programs for controlling DSLR and now mirrorless cameras, BackyardEOS (v3.2.2) and AstroPhotographyTool (v3.88). Both recognized and connected to the R6 via its USB port. 

Both programs recognized the Canon R6.

Another popular option is the ASIair WiFi controller from ZWO. It controls cameras via one of the ASIair’s USB ports, and not (confusingly) through the Air’s remote shutter jack marked DSLR. Under version 1.7 of its mobile app, the ASIair now controls Canon R cameras and connected to the R6 just fine, allowing images to be saved both to the camera and to the Air’s own MicroSD card. 

With an update in 2021, the ZWO ASIair now operates Canon R-series cameras.

The ASIair is an excellent solution for both camera control and autoguiding, with operation via a mobile device that is easier to use and power in the field than a laptop. I’ve not tried other hardware and software controllers with the R6. 

TIP: While the R6, like many Canon cameras, can be controlled remotely with a smartphone via the CanonConnect mobile app, the connection process is complex and the connection can be unreliable. The Canon app offers no redeeming features for astrophotography, and maintaining the connection via WiFi or Bluetooth consumes battery power. 

A dim red and green aurora from Dinosaur Provincial Park, Alberta, on August 29/30, 2021. This is a stack of 4 exposures for the ground to smooth noise and one exposure for the sky, all 30 seconds at f/2.8 with the Canon 15-35mm RF lens at 25mm and the Canon R6 at ISO 4000.

SUGGESTIONS TO CANON

To summarize, in firmware updates, Canon should:

  • Fix the low-level amp glow. No camera should have amp glow. 
  • Allow either dimming the Timer readout, turning it red, or just turning it off!
  • Add a battery display to the Timer readout. 
  • Expand the Interval Timer to allow up to 999 frames, as in the Time-Lapse Movie. 
  • Allow the Rate button to be re-assigned to more functions.
  • Default the Release Shutter w/o Lens function to ON.
  • Revise the manual to correctly describe how to stop an Interval Timer shoot.
  • Allow programming multiple long exposures by combining Interval and Bulb Timer, or by expanding the shutter speed range to longer than 30 seconds, as some Nikons can do.
The Zodiacal Light in the dawn sky, September 14, 2021, from home in Alberta, with the winter sky rising. This is a stack of 4 x 30-second exposures for the ground to smooth noise, and a single 30-second exposure for the sky, all with the TTArtisan 7.5mm fish-eye lens at f/2 and on the Canon R6 at ISO 1600.

CONCLUSION

The extended red sensitivity of the Canon EOS Ra makes it better suited for deep-sky imaging. But with it now out of production (Canon traditionally never kept its astronomical “a” cameras in production for more than two years), I think the R6 is now Canon’s best camera (mirrorless or DSLR) for all types of astrophotography, both stills and movies. 

However, I cannot say how well it will work when filter-modified by a third-party. But such a modification is necessary only for recording red nebulas in the Milky Way. It is not needed for other celestial targets and forms of astrophotography. 

A composite showing about three dozen Perseid meteors accumulated over 3 hours of time, compressed into one image showing the radiant point of the meteor shower in Perseus. All frames were with the Canon R6 at ISO 6400 and with the TTArtisan 11mm fish-eye lens at f/2.8.

The low noise and ISO invariant sensor of the R6 makes it superb for nightscapes, apart from the nagging amp glow. That glow will also add an annoying edge gradient to deep-sky images, best dealt with when shooting by the use of LENR or dark frames. 

As the image of the Andromeda Galaxy, M31, at the top of the blog attests, with careful processing it is certainly possible to get fine deep-sky images with the R6. 

For low-light movies the R6 is Canon’s answer to the Sony alphas. No other Canon camera can do night sky movies as well as the R6. For me, it was the prime feature that made the R6 the camera of choice to complement the Ra. 

Alan, September 22, 2021 / © 2021 Alan Dyer / AmazingSky.com  

Testing the Canon 6D Mark II for Deep-Sky


6D MkII on Cygnus

Following up on my earlier tests, I compare the new Canon 6D MkII camera to earlier Canon full-frame models in long, tracked exposures of the Milky Way.

A month ago I published tests of the new Canon 6D MkII camera for nightscape images, ones taken using a fixed tripod in which exposures usually have to be limited to no longer than 30 to 60 seconds, to prevent star trailing.

Despite these short exposures, we still like to extract details from the dark shadows of the scene, making nightscape images a severe test of any camera.

I refer you to my August 9, 2017 blog Testing the Canon 6D MkII for Nightscapes for the results. The 6D MkII did not fare well.

Here I test the 6D MkII for what, in many respects, is a less demanding task: shooting long exposures of deep-sky objects, the Milky Way in Cygnus in this case.

Why is this an easier task? The camera is now on a tracking mount (I used the new Sky-Watcher Star Adventurer Mini) which is polar aligned to follow the rotation of the sky. As such, exposures can now be many minutes long if needed. We can give the camera sensor as much signal as the darkness of the night sky allows. More signal equals less noise in the final images.

In addition, there are no contrasty, dark shadows where noise lurks. Indeed, the subjects of deep-sky images are often so low in contrast, as here, they require aggressive contrast boosting later in processing to make a dramatic image.

While that post-processing can bring out artifacts and camera flaws, as a rule I never see the great increase in noise, banding, and magenta casts I sometimes encounter when processing short-exposure nightscape scenes.


6D MkII at Four ISOs
The Canon 6D MkII at four typical ISO speeds in tracked exposures.

6D at Four ISOs
The original Canon 6D at four typical ISO speeds in tracked exposures.

5D MkII at Four ISOs
A Canon 5D MkII that has been filter-modified at four typical ISO speeds in tracked exposures.
For this test, I shot the same region of sky with the same 35mm lens L-Series lens at f/2.2, using three cameras:

• Canon 6D MkII (2017)

• Canon 6D (2012)

• Canon 5D MkII (2008)

Note that the 5D MkII has been “filter-modified” to make its sensor more sensitive to the deep red wavelengths emitted by hydrogen gas, the main component of the nebulas along the Milky Way. You’ll see how it picks up the red North America Nebula much better than do the two off-the-shelf “stock” cameras. (Canon had their own factory-modified “a” models in years past: the 20Da and 60Da. Canon: How about a 6D MkIIa?)

I shot at four ISO speeds typical of deep-sky images: 800, 1600, 3200, and 6400.

Exposures were 4 minutes, 2 minutes, 1 minute, and 30 seconds, respectively, to produce equally exposed frames with a histogram shifted well to the right, as it should be for a good signal-to-noise ratio.

Noisy deep-sky images with DSLR cameras are usually the result of the photographer underexposing needlessly, often in the mistaken belief that doing so will reduce noise when, in fact, it does just the opposite.

The above set of three images compares each of the three cameras at those four ISO speeds. In all cases I have applied very little processing to the images: only a lens correction, some sharpening, a slight contrast and clarity increase, and a slight color correction to neutralize the background sky.

However, I did not apply any luminance noise reduction. So all the images are noisier than what they would be in a final processed image.

Even so, all look very good. And with similar performance.

All frames were shot with Long Exposure Noise Reduction (LENR) on, for an automatic dark frame subtraction by the camera. I saw no artifacts from applying LENR vs. shots taken without it.

The 6D and 6D MkII perhaps show a little less noise than the old 5D MkII, as they should being newer cameras.

The 6D MkII also shows a little less pixelation on small stars, as it should being a 26 megapixel camera vs. 20 to 21 megapixels for the older cameras. However, you have to examine the images at pixel-peeping levels to see these differences. Nevertheless, having higher resolution without the penalty of higher noise is very welcome.


3 Canons at ISO 1600
The three cameras compared at ISO 1600. Note the histogram and region of the frame we are examining up close.

3 Canons at ISO 3200
The three cameras compared at ISO 3200. Note the histogram and region of the frame we are examining up close.

3 Canons at ISO 6400
The three cameras compared at ISO 6400. Note the histogram and region of the frame we are examining up close.
Above, I show images from the three cameras side by side at ISOs 1600, 3200, and 6400. It is tough to tell the difference in noise levels, the key characteristic for this type of astrophotography.

The new 6D MkII shows very similar levels of noise to the 6D, perhaps improving upon the older cameras a tad.

Because images are well-exposed (note the histogram at right), the 6D MkII is showing none of the flaws of its lower dynamic range reported elsewhere.

That’s the key. The 6D MkII needs a well-exposed image. Given that, it performs very well.


3 Canons Stacked & Processed
The three cameras in stacked and processed final images.
This version shows the same images but now with stacked frames and with a typical level of processing to make a more attractive and richer final image. Again, all look good, but with the modified camera showing richer nebulosity, as they do in deep-sky images.

The lead image at the very top is a final full-frame image with the Canon 6D MkII.


As such, based on my initial testing, I can recommend the Canon 6D MkII (and plan to use it myself) for deep-sky photography.

Indeed, I’ll likely have the camera filter-modified to replace my vintage yet faithful 5D MkII for most of my deep-sky shooting. The 6D MkII’s tilting LCD screen alone (a neck, back, and knee saver when attached to a telescope!) makes it a welcome upgrade from the earlier cameras.

The only drawback to the 6D MkII for deep-sky work is its limited dark frame buffer. As noted in my earlier review, it can shoot only three Raw files in rapid succession with Long Exposure Noise Reduction turned on. The 5D MkII can shoot five; the 6D can shoot four. (A 6D MkIIa should have this buffer increased to at least 4, if not 8 images.)

I make use of this undocumented feature all the time to ensure cleaner images in long deep-sky exposures, as it produces and subtracts dark frames with far greater accuracy than any taken later and applied in post-processing.


I hope you’ve found this report of interest.

With the 6D MkII so new, and between smoky skies and the interference of the Moon, I’ve had only one night under dark skies to perform these tests. But the results are promising.

For more tips on deep-sky imaging and processing see my pages on my website:

Ten Tips for Deep-Sky Images

Ten Steps to Deep-Sky Processing

Thanks and clear skies!

— Alan, September 7, 2017 / © 2017 Alan Dyer / amazingsky.com

 

%d bloggers like this: