Sunset in the City — This is Only a Test!


This is one for the time-lapse geeks!

One of the trickiest subjects for a time-lapse sequence is a smooth and seamless day-to-night transition. Exposure times vary from fractions of a second before sunset to several seconds at night fall.

How to do it? Manually shifting exposures is too much work and prone to error. Putting the camera on Automatic can work but inevitably results in an effect known in the time-lapse world as “flickering.” The camera’s automatically-judged exposures aren’t consistent from frame to frame so the final movie shows minor bright/dark flickering, making it look jerky.

For this test sequence of sunset over the Calgary skyline, I tried a new toy for the first time, as a solution.

The device is called the Little Bramper (for Bulb Ramping). It is a custom-made intervalometer that fires the camera shutter every few seconds (at whatever interval you desire). Nothing new there. But what’s unique is that it can be set to slowly increment the exposure time by as little as 1/1000th of a second from frame to frame, gradually increasing the exposure (“ramping” it) to accommodate the darkening scene. The result is a smooth transition from day to night with no flickering.

This was my first use of the Bramper and it wasn’t without its glitches. The shortest exposure the Bramper can provide (it always controls the camera thru its Bulb setting) is about 1/10th of a second (I had no idea camera shutters can fire as quickly as that even on Bulb).

But at the beginning of a sequence like this, with a bright sky, achieving that exposure (still quite long) means using a small f-stop, a slow ISO speed, or a neutral density filter, or all of the above. But as the sky darkens and exposures lengthen, exposures would become too long to fit within the desired interval between frames (typically no more than 5 to 10 seconds for a smooth sequence). So, to shorten the exposures you then have to open up the lens, switch to a faster ISO, or remove the ND filter, while also commanding the Bramper to quickly reduce its exposure time, all in one exposure cycle (i.e. 5 to 10 seconds) so as not to lose or ruin frames. Takes some coordination and practice (hit the Bramper’s button, adjust the camera, all within 5 seconds), and I didn’t get it right the first couple of times.

But overall, for a first test, the sequence turned out very well. The $80 Little Bramper does the job, though it does take careful monitoring through the sequence, not just to perform the exposure swaps, but to also watch that the ramping rate (adjustable on the fly) matches what the scene is doing and you aren’t under- or over-exposing. It’ll take a little more practice, but the results certainly are worth it.

It’s another neat tool in the time-lapse arsenal.

— Alan, August 10, 2011 / Movie © 2011 Alan Dyer

Milky Way in the Mountains


It’s rare to get such a clear night in the mountains but I used the opportunity last Thursday night to shoot the Milky Way in a twilight scene in Banff National Park.

I took this a little later on the same night as the previous blog’s image of the setting Moon. The location is the Vermilion Lakes, a familiar scenic spot for classic views of Banff and Mount Rundle reflected in the water, at far left. It is one of the few places in the mountains where you can look south over a low mountain skyline (to see the southern Milky Way) and over still water (to get reflections).

For this shot I used a fish-eye lens to record most of the sky and the summer Milky Way arching over the water. The sky was dark enough to show the Milky Way but still had a lingering blue tint from the last glow of deep twilight. The yellow glow at left to the east is from the urban lights of Banff.

The still image is one frame of 220 shot over 4 hours for a time-lapse video, for projection in a full-dome video-equipped planetarium. Just so happens we’re building one in Calgary to open in early 2012.

— Alan, August 9, 2011 / Image © 2011 Alan Dyer

 

Auroral All-Sky Dance


Here is nearly two hours of auroral dancing compressed into 25 seconds.

This was the “all-sky” aurora of August 5/6, 2011, widely seen over North America but perhaps (from early reports) best from the western half, especially Canada, favoured for Northern Lights due to our latitude.

I shot this with the 8mm fish-eye lens and the Canon 5D MkII. The movie consists of 255 frames, each 24 to 30 seconds in exposure duration, taken one second apart. ISO speed was 1600 and aperture f/3.5. The playback frame rate is 10 fps.

This display was quite chaotic, without the graceful rippling curtains present in many displays, but rather huge patches of sky turning off and on. This is typical of an aurora in the declining part of the storm — it had already been raging for several hours by the time it got dark here in Alberta.

Nor was the display very bright, so the longer exposures needed to record it well further blur any fine motion. Nevertheless, you get a good idea of the intense activity this aurora displayed. The magnetosphere was jumping last night!

— Alan, August 6, 2011 / Movie © 2011 Alan Dyer

The Milky Way from Chile


This was the Milky Way as it appeared toward the end of a long night of non-stop shooting from Chile. The centre of the Galaxy lies directly overhead and the Milky Way stretches from horizon to horizon. This is one of the sky’s greatest sights, and this is an ideal time of year to see it. But only if you are in the magic latitude zone of 20° to 30° south.

In this shot, another skyglow stretches up from the eastern horizon at left – that’s the Zodiacal Light, so obvious from this latitude. It’s sunlight reflected off comet dust in the inner solar system, and heralds the coming dawn twilight.

My tracking platform – the device that allows a camera to follow the sky for a time exposure – is at lower right, with a second camera taking telephoto lens shots of star clusters in the Milky Way.

I took this shot with the Sigma 8mm fish-eye lens and the Canon 5D MkII camera that was on a fixed tripod – it was not tracking the sky. But the 45-second exposure at ISO 3200 was enough to bring out the Milky Way in all its glory. This frame is one of 660 or so that make up (or will once I assemble it) a time-lapse movie of the Milky Way turning about the pole and rising through the night. The fish-eye format makes it suitable for projection in a planetarium dome.

– Alan, May 2, 2011 / Image © 2011 Alan Dyer