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Variable shutter strobe effect via other means


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#1 Larry Miles

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Posted 16 December 2013 - 04:53 PM

Hello, all. I hope I've posted in the most appropriate forum.

 

Is it possible to achieve the strobe effect one gets with a variable shutter set at 90 degrees or less by shooting at a higher frame rate but in the transfer, or, more likely, in post, skipping frames? For example, shooting at 48 frames per second and only using every other frame or 72 frames per second and only using every third frame (obviously this would be for a 24 fps edit).

 

If so, are there any tricks or pitfalls to doing so?

 

Thank you.


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#2 Chris Millar

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Posted 16 December 2013 - 06:06 PM

Cant see any reason it wont work in terms of the logic.

 

The only hassle might be having to write a script or bodge the functionality to sort the odd and even frames into a coherent run of images, but maybe its as simple as a tick box in some application already?

 

Of course you already know you'll have shot twice as much footage that you need, perhaps not an issue in a digital environment. Also the offshoot (literally?) is that you'll actually end up with two possible streams to choose from (odd or even), both the same 'film' but both made of completely different image information/samples.  :blink:


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#3 Carl Looper

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Posted 17 December 2013 - 06:33 AM

Yes - that will work but it's a bit of a waste of film. Surely borrowing a camera with a variable shutter is a better idea.

 

One alternative (but not as good) is to shoot 24 fps, and then in the digital domain compute the optical flow and then deconvolve the estimated motion blur by half the length, for each frame. Not sure if something like this available in After Effects etc.

 

C


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#4 Chris Millar

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Posted 17 December 2013 - 07:12 AM

From what I've read (not much yet) is that optical flow cannot give you a deterministic interpretation that will allow exactly what you're talking about, of course it'll get you somewhere - that is again, of course if you can get yourself there in the first place.

 

Vector calculus anyone ?  :wacko:  ;)

 

Like two cameras can give you parallax that allows depth/distance ambiguities to be resolved with much more certainty there is likely an analog for optical flow, maybe shooting two shutter angles from the same lens concurrently would allow optical flow to work to more (at least apparent) precision.

 

Even better would be to shoot 360deg at the fastest frame rate you can manage - you could then dial in your shutter angle in post with a resolution of: outputFrameRate/captureFrameRate


Edited by Chris Millar, 17 December 2013 - 07:13 AM.

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#5 Phil Rhodes

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Posted 17 December 2013 - 10:35 AM

Since you can't deblur images with any real reliability, it can't really be solved in software.

 

You could, of course, illuminate your scene with a synchronised strobe light, although if you used a xenon flash tube type strobe the effective shutter time (and amount of light) would really be very small.

 

P


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#6 Larry Miles

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Posted 18 December 2013 - 08:26 AM

Thank you all for your replies.


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