Trying to fix issue with mask feather vs. mask opacity.

Question

I'm playing with that trick where these movie theater curtains open up to reveal an image (in this case a company logo) behind it. The challenge is getting the blend where the curtain doesn't have an ugly black shadow before the mask animates, shown in the upper-center of the image above.

The problem is when I lower the mask expansion to remove that shadow the green tint of the original animation returns. I get either ugly shadow and no green or no shadow and green.

Do I need to make a choice or is there another step to balance these options out?

Rick Gerard · Accepted Answer

You will have to explain where the green tint comes from. I don't see any effects on Layer 1 (the curtains). I assume that the MP4 is stock footage with green behind the curtains. If that is the case, you probably don't need an animated mask. You need to use Keylight to create transparency.

I found Curtain 2550 on Vimeo. It looks like the clip you are using. All you need to do is apply Keylight and carefully tweak the settings to get a clean edge.

Mylenium · Answer

You need to work with duplicates, that's all I'm saying. You have to use your mask twice - once to produce the darkening at the edge and a second time, but without feathering. The darkening would ideally be inside the pre-composition and in order to fully control the situation and not rely on "it happens because there's transparency" you'd also add a black solid underneath. Then in the parent comp you'd re-use the mask to remove your green. If you want to be super smart about it, in fact you wouldn't even use the mask directly, but rather create it in a separate sub-comp (unfeathered) and then use it as an Alpha/ Luma Matte. That way you can re-use it directly multiple times without needing copy & paste of masks and feathereing would be done by blurring the respective matte layers.

Mylenium

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