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Activity Forums Adobe After Effects Alpha Channel not dispalying

  • Alpha Channel not dispalying

    Posted by David Tannenbaum on September 18, 2008 at 4:40 pm

    I can’t get the alpha channel to display.

    When I click on the channel display to show me the alpha all I get is white. I would think that there must be alpha channels in my comp because I have imagery that has transparency where you can see images behind other images, through images, and images that have irregular shapes.

    I thought that I read that AE automatically creates alpha channels from empty areas.

    What gives?

    David

    Darby Edelen replied 17 years, 8 months ago 3 Members · 5 Replies
  • 5 Replies
  • Darby Edelen

    September 18, 2008 at 4:59 pm

    [David Tannenbaum] “What gives?”

    You’re looking at the alpha channel of your entire composition. Which is the alphas of all of your layers blended together. Which will often be entirely white.

    If you want to look at the alpha of just a single layer then you need to double click that layer to open it in the layer window and then view the alpha channel.

    Darby Edelen

    NVIDIA
    Santa Clara, CA

  • Jason Milligan

    September 18, 2008 at 5:09 pm

    Transparency within the imagery of a file is not the same thing as an alpha channel. An alpha channel is transparency of the entire file, not it’s individual elements. Importing a layered PSD file as a composition would import each layer as a file with individual alpha channels. Importing a flattened PSD would only use the collective alpha of all the layers or none if the background layer is opaque.

    What format is the file you are importing?
    JPEG cannot support alpha channels.
    Your file format should be PSD, TIFF, targa, or some other format that supports alpha and should be saved with an alpha channel. This is not always automatic.

    So in short, your file most likely does not have an alpha channel and that is why AE is not recognizing it (or the alpha channel is all white because the collective elements in the file are fully opaque).

    I’m guessing here, but it sounds like you want to have interactivity between layered elements with multiple alphas. The solution is simple. Import that PSD as a composition. Then you will get all of your layers as separate footage with their own alphas.

  • David Tannenbaum

    September 18, 2008 at 5:28 pm

    I imported the PSD file as a composition(cropped layers)

  • David Tannenbaum

    September 18, 2008 at 5:51 pm

    How come my sub comps (which have indivdual layers from photoshop ) maintains the alpha for each individual layer; while my final comp seems to have no alpha channel (or as you said, the alphas are combined to one big channel displaying as white?)

  • Darby Edelen

    September 18, 2008 at 11:18 pm

    [David Tannenbaum] “while my final comp seems to have no alpha channel”

    Your final comp has alpha information, it’s just an entirely ‘opaque’ alpha channel. There is a layer somewhere in your pre-comps or in your final comp that is entirely opaque. Perhaps a solid layer, perhaps video footage?

    Darby Edelen

    NVIDIA
    Santa Clara, CA

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