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Time lapse and narrow shutter angle


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#1 Patrick Cooper

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Posted 24 December 2006 - 04:27 AM

Whenever I have done time lapse, the shutter has always been open in the standard shutter angle (not exactly sure how many degrees that is but the shutter speed is roughly 1/48th of a second.) I am considering doing some time lapse shortly with the shutter angle reduced by about a quarter. As everyone knows, a reduced shutter angle does not always produce the best results when running film at standard frame rates - ie - that 'choppy' look. I am wondering how prominent this effect is in time lapse...I guess it depends on the interval time.

When doing time lapse, one minute intervals seem to work best for me when i want to reveal the movement of shadows. If I reduce the shutter angle so it is about a quarter open while doing one minute intervals, would the movement of shadows appear as smooth as if the shutter angle was fully open?
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#2 Nick Mulder

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Posted 24 December 2006 - 05:37 PM

If you take your shutter angle and divide it by 360 and then multiply that number with the reciprocal of your fps you will get a time in seconds that the shutter is open - take any stills camera and test that exposure to see if you like the effects ...

If you are using a rotating shutter on a camera not set up for time-lapse then there will be 2 periods per frame when the shutter is half exposing the frame, if anything in your exposure were to flare up in terms of light intensity during these times then the shutter will cast a shadow...

Either you need to shoot constantly lit subjects or modify your shutter/drive system so that it whips the shutter around in these transitional periods and you can then enter the mark/space times (expose/not-expose times - which added = your fps) as opposed to just the fps (and whatever shutter angle is directly slaved from this) ...

hope this makes sense :)

Edited by Nick Mulder, 24 December 2006 - 05:40 PM.

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#3 Phil Savoie

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Posted 25 December 2006 - 01:19 AM

I?d suggest you lengthen your exposure, either by interval frame rate or shutter angle. To loose the ?steppy? look you want images that blend together. Long exposures of ΒΌ to 1 second will give you frames that ramp nicely together in post.

The frame rate of any given subject is something so variable it?s often learned via trail and error. Experiment with both shutter speed and frame rate if you like ? but with today?s inexpensive computerized post tools like Final Cut you can ramp away to your hearts content. Because of this it always better to have more frames to ramp/play with.
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#4 Patrick Cooper

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Posted 25 December 2006 - 08:41 AM

Phil, honestly, I would prefer to use the usual slow shutter speed for these time lapse shoots but I am using 100D in bright sunlight. Ideally, I would buy a suitably sized ND filter but I am filming a test and sending the film off for processing before January and many camera shops will be closed during this period. I do have some ND filters of my own but they are too small to fit on this lens and would vignette anyway if a step down ring was used. If I can't find a camera store that is open within the next few days, I'll be forced to narrow the shutter angle when I do the time lapse.
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#5 Nick Mulder

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Posted 25 December 2006 - 03:55 PM

yep, the xmas period can be a hassle if you need something photographic wise - some shops here close for weeks...

My only suggestion to try to get a smoother picture (keeping shutter angle as high as you can) is to maybe pull process the film a stop or two, I dont know the effects on that stock but generally I think its near the opposite of pushing - lower contrast and therefore maybe more shadow detail ...
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#6 Satsuki Murashige

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Posted 26 December 2006 - 02:18 AM

I would prefer to use the usual slow shutter speed for these time lapse shoots but I am using 100D in bright sunlight. I'll be forced to narrow the shutter angle when I do the time lapse.


Won't increasing the shutter speed essentially ruin your test by introducing an unwanted variable into the look of the footage, given that you say you prefer a slower shutter speed anyway? If so, then ND is the way to go.

If you can't get a suitable glass filter in time, then one (admittedly ghetto) option is take a gel sample pack, cut out ND's in the shape of your lens's rear element, and attach them with snot tape. This is assuming you don't have a camera that can take filters behind the lens like the Bolex. Just remember to stop down to T8 or so, as the thickness of the gel will shift your focus slightly.

I wouldn't consider pulling the film, since this would throw another unwanted variable into the footage and cost you more money.
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