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Probe changing brightness value from one layer and apply it to another
Hello. I’m compositing a video on a projection screen. The projector emits white light and somebody is waving its hand in front of it to imitate the flickering of the screen. After I composite the video the screen around is flickering. Can you help me with the solution how to get the changing brightness value and apply it to the video, so it flickers the same way? Thank you!
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3 Replies
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So you are looking for a way to transfer the brightness settings from one layer to another? Not sure how it works in after effects but usually in Adobe Photoshop, you can select a specific layer and then set the brightness setting, you go to Image -> Adjustments -> Brightness & Contrast. And you can do it on each layers. But are you looking to do something similiar in After Effects?
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Hi, I’m not trying to set the Brightness manually, but rather define a section on the video that “samples” every frame, assigns it a brightness value and then transfers it to another layer.
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Broadly speaking, you’ll want to first set up the effect you’re looking for. Maybe you want to use the Exposure effect, or masked solid with a blend mode, or something to create the lighting effect you want.
Then, you’ll want to experiment a little to understand the relationship between the brightness in the input image and the values they should drive in your effect.
Finally, you’ll use a sampleImage() expression to drive that value, based on the sampled pixels your first layer.
Here’s a sample from the incomparable Dan Ebberts, using the brightness of one layer (clouds, in his case) to affect the flare on another: https://www.motionscript.com/design-guide/obscuration.html
If you can post a short sample video or even a few sample still frames, we could probably help more concretely.
motionscript.com
Dan Ebberts's Expressioneering Design Guide
Dan Ebberts's resource for After Effects scripting and expressions
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