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Posterize time and make each new frame wipe on

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Perry KrollPosterize time and make each new frame wipe on
by on Jul 5, 2011 at 10:15:42 pm

Hello wonderful people of Creative Cow! Long time lurker here with a question... It's a simple concept, but I can't quite wrap my head around an easy way to do it.

Say I have a comp at 23.976 fps. I'd like to posterize time (i.e, reduce the apparent frame-rate of a piece of video) down to like 6 fps or so, and have each new frame of video very quickly wipe on. The wipes would happen over the course of 3-4 actual frames of video. Imagine a vertical wipe on transition having over and over again to reveal each new frame on top of the previous one.

The result would look something like an old monitor with a very poor refresh rate, or the feed from a satellite that has to download a few times a second. I'm looking to use this effect in some graphics I'm making for computer screens at a military HQ in a short film.

Any ideas for how to make this effect fairly automatic to apply?

many thanks!


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Walter SoykaRe: Posterize time and make each new frame wipe on
by on Jul 6, 2011 at 1:07:16 am

[Perry Kroll] "Say I have a comp at 23.976 fps. I'd like to posterize time (i.e, reduce the apparent frame-rate of a piece of video) down to like 6 fps or so, and have each new frame of video very quickly wipe on. The wipes would happen over the course of 3-4 actual frames of video. Imagine a vertical wipe on transition having over and over again to reveal each new frame on top of the previous one."

Tricky!

Here's how I'd approach it.

You need two layers of the footage, each with posterize time to half the frame rate of your desired end result. In the example above, you'll need two layers at 3fps. Offset one of the layers by 4 frames (pre-posterize time).

Now, create a separate precomp twice as high as your frame size. Give it a black background and create a white solid that's the normal frame size (so the upper half of the double-high frame is white and the lower half is black). Put that in a comp at the regular frame size, and animate and loop it with the offset effect to create a black and white rolling animation.

Use the black and white rolling animation as a luma matte on the top layer of your footage in the original comp.

So what does all this do? The black and white rolling animation wipes the upper version of your footage on and off, alternately revealing the upper version and the lower time-offset version of your footage, giving you the single frame scanning effect you're looking for.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
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Perry KrollRe: Posterize time and make each new frame wipe on
by on Jul 6, 2011 at 6:03:35 am

This is pure genius. I had thought of using two layers with half the rate for posterize time, but I was thinking I'd have to use some kind of oscillating expressions and the linear wipe transition. Your solution is awesome. Thanks! Now to find a way to automate the offset filter and the frame-rates and tie the whole thing to a control null... hmmmmm. Off to tinker...


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