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Time to be with loved ones

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I'm planning a long road trip (east coast to west coast, about 45 hours of driving) and am thinking about shooting a time-lapse video of my drive.

As I can expect the light levels to change pretty drastically throughout the day (especially through sunset), how do I adjust my exposure to ensure smooth video?

If I set the camera on a program mode, the camera will compensate for the changing composition, which will cause flicker.

However, if I set the camera on manual mode, I can only adjust periodically (gotta keep my hands on the wheel), so I'm expecting that the exposure might occasionally be off by more than the stop or two recoverable in post.

Where's the middle ground? Should I just shoot in manual, adjust periodically, correct in post, and hope that I don't lose highlight or shadow detail? Should I shoot in a program mode and perform the same correction?

Since I'm planning to shoot tethered, is there a way to control exposure with the computer? Can I get metering information from a tethered (Nikon) camera, so that I could find/write a script that would smoothly adjust the exposure?

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Just be careful not to hit Walter White (photo.stackexchange.com/questions/6914/…) on the way... 8-) –  ysap Jan 14 '11 at 4:20
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5 Answers

up vote 11 down vote accepted

tl;dr: There is currently no 'foolproof/plug-n-play' solution to this problem (yet!). All of the currently available options have trade-offs which must be evaluated before jumping in.


This is a huge problem which is frequently discussed in the timelapse community. As of this writing there are not 'foolproof' solutions, though there are a good number of us who are attempting to create various 'plug-n-play' solutions to the problem.

As stated elsewhere, all automated modes tend to introduce a rather annoying level of flicker, especially during dawn and dusk when the light changes especially rapidly. While to some extent this can be managed with software that 'equalizes' the light levels across multiple frames and reduces flicker in post production for a short timelapse, the longer the timelapse is, the more problems are introduced in that the level of computer which can accomplish this task without simply breaking down and weeping openly is quite expensive. Additionally, whether these types of software are capable of doing a 'reasonable' job at the task of removing flicker is hotly debated by some.

One solution that a lot of us have had success with is to take bracketed frames instead of singles. This gives the option of using fading in post production to adjust in a relatively seamless way for the extreme changes that can occur. Depending on your camera you may be able to adjust for up to +4/-4 stops, giving you an effective dynamic range of 8 stops (full day to full night is approximately 12 stops, YMMV depending on time of year, location on the planet, etc.). Shoot that in RAW (gulp!) and you can batch process to add stops even beyond that. You'd have to experiment in order to see if the motion of your vehicle causes too many syncing problems, but I suspect that since you'd be fading between large chunks of frames, the syncing problems wouldn't be that bad. Obviously this is less than ideal in other ways, namely file size, so as always there is a trade-off to be evaluated.

I believe it would be possible to code a software solution to provide intervalometer functionality as you asked about. The problem that would need to be solved is that the software-based intervalometer would also have some sort of powered light sensor which would tell the computer what to adjust the shutter speed to. Either that or you could (hypothetically) build an algorithm that generates an appropriate curve to simulate the falloff of light as full-day goes to full-night. Then this algorithm could be used to automatically adjust shutter speed in a 'dumb' manner (e.g. it doesn't actually know what the light level is). All of this leads to the 'nuclear option' of options (at least as of this writing, anyway)...

What I have chosen to do is probably even an order of magnitude more extreme than anything above... I built my own intervalometer which includes a built in light meter and can adjust the shutter speed shot to shot as the lighting levels change. This is- by far- the most reliable way I've found to handle changing lighting conditions, and with it I've been able to get flicker-free full-day to full-night timelapses. But naturally the trade-off is that this is a home-brew device, so an electronics background (or a willingness to learn), the ability to code, or re-purpose others codes, a couple-hundred dollars worth of electronics parts and a soldering gun is required for this solution.

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Feel free to PM me if you're really interested in rolling your own hardware solution. I've got some excellent resources which can help point you in the right direction. –  Jay Lance Photography Jan 14 '11 at 6:48
    
I'd also highly recommend the community over at Timescapes.org: timescapes.org/phpBB3/index.php, which I'm also involved in pretty heavily, if you hadn't guessed by the novel above. :-) There's a lot of us trying to solve these kinds of problems, and there's a lot of really interesting cutting-edge solutions being worked on by various folks... –  Jay Lance Photography Jan 14 '11 at 6:50
    
I like the bracketing idea, and thought about the time-based exposure. Now I just have to figure out the control issue. –  Evan Krall Jan 14 '11 at 7:09
    
Before I built my intervalometer/light meter I got some surprisingly (to me) nice stuff with bracketing/fading between the different brackets in post. My camera gives me the option of 'Small, Medium, or Large' RAW files, and Small is still bigger than 1080p, so I just went with that, dumping straight to my laptop via a USB cable. Can't say I tested that solution with a 10+ hour timelapse, but I used that solution with no issues for 4-5 hour timelapses for a year while I built the intervalometer. –  Jay Lance Photography Jan 14 '11 at 7:20
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I'm not sure if your camera has an equivalent mode, but on my Pentax K-7, I'd put the camera into TAv mode, where I set the shutter speed and aperture but the camera chooses the ISO. (See comments: Craig Walker says that on the Nikon D90, you put the camera in manual mode — M on the dial — and enable auto-ISO in the menu for the same effect.)

Then, I'd a) set ISO to change in 1/3-stop increments so the differences are small and b) constrain the range of auto-ISO tightly, maybe ISO 200 to 1250. That still gives a couple of stops of latitude, but keeps exposure from changing too dramatically.

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My Nikon D90 has a similar feature. –  Craig Walker Jan 14 '11 at 4:18
    
Figured it would. Since there's no TAv on the dial, is it done through turning auto-ISO on in M? –  mattdm Jan 14 '11 at 4:19
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It's set through the menus (Shooting->ISO Sensitivity Settings->ISO sensitivity auto control) and is independent of the shooting mode. You can use it in auto/Program mode (P), manual (M), aperture priority (A), or shutter priority (S). I don't know how it picks which combination of ISO/shutter/aperture in the automatic/priority modes. –  Craig Walker Jan 14 '11 at 4:25
    
I think that's "yep", not "nope". :) With "ISO sensitivity auto control" on, in M you would have the same effect as turning the dial to TAv on Pentax. Turning it off and leaving the dial on M would be like Pentax's M always is. And P/S/A act just like Pentax's P/Tv/Av, where ISO is automatic or not, depending on a menu setting. (Or quickly changed from automatic to fixed by holding the ISO button and turning a dial — I assume that's also the same.) Basically, different ways of telling the camera to do exactly the same thing. –  mattdm Jan 14 '11 at 4:34
    
Gotcha, I misinterpreted TAv. –  Craig Walker Jan 14 '11 at 5:12
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Your answer might just come from post-processing. In Lightroom there's a feature called "Match Total Exposures." I found this description on what it does:

You can use this command to match the exposures across a series of images that have been selected via the Filmstrip. Match Total Exposures will calculate a match value by analyzing and combining the shutter speed, lens aperture, ISO speed the photos were captured at, plus any camera-set exposure compensation. It then factors in all these camera-set values, combine them with the desired exposure value (as set in the most selected image) and calculate new Lightroom exposure values for all the other selected images. I find that it can often be used to help average out the exposure brightness in a series of photos where the light values were going up and down during a shoot

Disclaimer: I've never tried it. I just went poking through Lightroom for a feature that would help.

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I would tend to go full auto. Even without the major changes in lighting throughout the day, you're going to be changing direction (and thus angle to the sun) and going trough areas of light and shadow (mountains, trees, vehicles) constantly. That'll be a lot to adjust on the fly; you pretty much can't do it while driving. Even if you control and adjust your manual settings regularly, you'll still probably end up with flicker from changing light... so why not go auto and save the hassle?

You might want to do some tweaks as you go even while in auto, in particular to your ISO. That will be a good way to get the similar aperture/shutter combinations (both critical in a moving vehicle) as day turns to night.

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Some flicker from changing light is OK - I don't want every image to be the same average luminosity. –  Evan Krall Jan 14 '11 at 5:10
    
I agree. It would be better to capture each scene with a full dynamic range. If there are exposure artifacts or side effects (like graininess at night), those can be better addressed in post. –  wallyk Jan 14 '11 at 5:25
    
Word of warning for Canon users out there..."Full Auto" modes in Canon tend to always use JPEG. RAW images are usually only available in manual and semi-automatic modes. –  jrista Jan 14 '11 at 6:56
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Just saw a video timelapse and explanation by Philip Bloom - for a 36 hour Timelapse -

http://philipbloom.net/2009/10/20/36-hour-timelapse-using-the-canon-7d/

I think that is the answer and is pretty simple - he found shooting with auto aperture, auto shutter speed and auto ISO giving satisfying results, although he would stick to just auto shutter speed next time.

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Hi Clarke! Welcome to Stack Exchange. While this is helpful, it'd be even more awesome if you could briefly summarize the info from the link, in case Philip Bloom's site goes down (or just gets reorganized) and the link dies. –  mattdm Dec 10 '11 at 23:14
    
Philip is using a lens with very short focal length (10mm), I guess aperture changes might become more noticeable with longer focal lengths. –  Imre Dec 11 '11 at 7:33
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