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High FPS footage to 25p - real-time NOT slowmotion

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Jack Benson
High FPS footage to 25p - real-time NOT slowmotion
on May 6, 2012 at 1:31:05 pm

If one is filming in 50fps, how do you use that footage at 25p, without conforming it (so the footage is still in real-time).

If the shutter speed, when shooting at 50p is 1/100 of a second (as it is shot at this fps for the purpose of slow-motion), and the NLE is importing 50p to a 25p project, I assume it removes every other frame resulting in 25p footage with an incorrect shutter speed (of 1/100th of a second).

This is a very applicable subject in reference to speed ramping high fps footage to real-time.

So, IF the above is correct, how do you correct the shutter speed problems?

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Angelo Lorenzo
Re: High FPS footage to 25p - real-time NOT slowmotion
on May 6, 2012 at 9:08:20 pm

There are three main ways of re-timing: dropping/repeating frames(dropping in your case), frame blending (simple, kind of messy looking unless you're trying to speed up footage like 400% then it works well, not so hot for slow motion), and optical flow blending.

NLEs like Premiere allow you to choose between blended or frame dropping.

If you have After Effects, it includes a Time Warp plugin which, if I recall, has some optical flow technology from The Foundry's Kronos plug-in. You would interpret at 25fps so your footage was in slowmotion, then apply the effect for 200% speed, basically allowing the plugin to take over re-timing from the NLE. This plugin also includes motion blur to reduce the heavier shutter artifacts.

Twixtor is a third party plugin with similar features. Is one better than the other? They're both tuned to react slightly differently. Twixtor handles deep slow motion better in every case I've used it.

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