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Day to night exposure for timelapse shoot


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#1 Jamie Kennerley

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Posted 02 March 2008 - 02:00 PM

I'm assisting on a timelapse shoot at the end of the week, for a commercial of some sort. It's going to be a digital stills shoot in the end, which seems to make sense. It's an exterior, from day to night.

We figure we'll set everything to manual (WB, Exposure, Shutter) as changing halfway through is likely to cause a noticeable exposure, colour temperature or depth of field change.

But how do we deal effectively with the light level change from day to night?! We obviously can't be adjusting all the way or we won't have an effective fall towards night, but then if we're still on our day exposure at night we're going to be in trouble...

I'm not talking about the need for an intervelometer etc, as I believe the camera will be controlled from a computer, just dealing theoretically with this day to night change.

I'm sure there's no magic solution to this, but can anyone advise?
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#2 Will Earl

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Posted 04 March 2008 - 05:23 AM

The last time I did a night-to-day timelapse (shot HD) I set the exposure to auto. As the light became brighter I'd switch in some ND and the camera would adjust the iris till it got to the same levels as before the ND when in - it worked perfectly.

If your trying to maintain a short DOF then setting the iris to auto probably won't work for you, but on a wide shot of a landscape it'll work fine. If you do need to maintain a consistent DOF then you could set the shutter to auto.
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#3 Aaron Medick

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Posted 04 March 2008 - 01:30 PM

I believe the accepted way to do this is to hide your adjustment(s) in a 3 frame dissolve in post. You set exposure for the day let the sun set. Adjust the exposure for night. Depending on location/subject you may need to do another adjustment to compensate exposure for dusk. Make sure you don't move the camera while adjusting exposure. Use a good tripod, head and few sand bags. Don?t set up on a moving object like a suspension bridge, tall building, etc. if you do you will have to run the footage thru a stabilization software in post.

Good Luck,
Aaron
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#4 Hugh Macdonald

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Posted 18 March 2008 - 09:08 AM

My initial reaction to this would be to shoot it with the settings on Auto. Then, because it's going to fluctuate frame to frame, apply a deflicker to the result. You should end up with a nice smooth transition.
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#5 Tom Lowe

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Posted 18 March 2008 - 10:05 AM

I cannot imagine that setting the DLSR to auto exposure will work. In fact, it sounds like a very bad idea. As the light changes, your exposure settings will jump all over the place, up and down and up and down, and back and forth between frames, leaving you with a flickering mess.

Can you tell us more about the shot? For example, if you start your timelapse about 1 or 2 stops over, you can let it get darker, and sometimes the streetlights and cars, etc, will compensate. This assumes you are shooting in a city with lights.

The other unknown is your computer controlling the camera. If this connection can MANUALLY ramp the shutter in very small increments, it might work. But if you are relying on the camera's light meter, my experience is that it jumps all over the place as clouds move, cars come by, subject matter changes, etc.

If I can offer any advice, feel free to pm me and we can chat by phone.
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#6 Will Earl

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Posted 18 March 2008 - 02:48 PM

In fact, it sounds like a very bad idea.


I agree. Maybe I should have added 'it-depends-on-the-shot' to qualify my suggestion a bit better.

Here's an example of timelapse shot with the exposure controlled automatically... (spot the artifacts - there are some in there, none however are related to exposure)

http://www.earlyworm...ise_-_2006.html

This worked because the lighting changes were rather low frequency changes, it will not work very well with high frequency exposure changes.
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#7 Jamie Kennerley

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Posted 23 March 2008 - 10:14 AM

Many thanks for your replies on this. Apologies that I haven't been back on this topic for a while, but there turned out to be no money for an assistant so I didn't work on the project in the end!

So, I can't be specific about how the shoot worked, but from what research I did do in the run-up, I came to similar conclusions to Aaron - that the best approach is to adjust exposure to register your main lighting changes correctly. Let your day fall under, effectively getting a fall out by under-exposure; open up to adjust for the real sunset and let it fall to night; open up again for night. Then smooth the transition in post.

There's an interesting article here:

http://www.soc.org/o...09_timelps.html

Thanks again,

Jamie
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