How do I add an alpha channel to an adjustment layer? 1

[dammit]

I'm trying to make an adjustment layer with an animated alpha channel. I have a normal movie; R,G,&B channels are the same- so I tried to use "set channels" to remap the red channel to the alpha channel. It worked, but the catch is- that's an *effect,* not a permanent change. So once I turn it into an adjustment layer, all the layers below it also get alpha channels based on the red channel, which isn't what I want. I don't see any way to get around this.

Except to import a movie with the alpha channel already in it, but that seems impossible. I've tried outputting Quicktime movies from After Effects, after giving them alpha channels the same way as above, and then importing them again- the alpha is gone.

 

[howiem]

Sounds like you just need to precompose the layer with the Channel shift on it, perhaps?

Say you have a photo on one layer, and you want some transparent text to move across it, just blurring the background (see

http://howiem.com/randombits/dammit.png

for example), you'd do something like this:

Import a photo and drop it into a new composition.
Create a solid layer above it, and add a text effect to it. Adjust to taste, and animate if you like. This can be fine-tuned later.
Precompose the layer: with the text layer highlighted hit ShiftCtrl-C or select Precompose from Layer menu.
When asked, say 'Move all attributes...'. This means the new composition created has not just the Solid layer with the Text effect it, but also the Text effect itself with the Alpha channel it creates.

Then when you turn the precomposed layer into an adjustment layer it'll only affect the areas covered by the text in underlying composition.

Does that make sense? [or do you know all this and it's a different thing entirely?]