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Activity Forums Adobe After Effects Stencil alpha doesn’t quite uphold once new layer added below

  • Stencil alpha doesn’t quite uphold once new layer added below

    Posted by Alex Ezorsky on March 26, 2017 at 3:30 am

    Seems like a simple problem here. I have an image of these roots. I’m trying to add a dirty fractal noise layer with a color burn blend mode to get a dirty look. Of course I need the fractal noise layer to be alpha matted to the roots. But every time I do it ads a thin white edge to the roots that wasn’t there before.

    It’s not just white though, it seems to be increasing the alpha. This should be theoretically impossible if the top layer (a duplicate of the roots) is stenciling all layers below. And yet somehow it is.

    Any idea what’s going on?

    Thanks

    Darby Edelen replied 9 years, 4 months ago 3 Members · 2 Replies
  • 2 Replies
  • Kevin Camp

    March 27, 2017 at 4:55 pm

    you may be encountering some of the issues with blending modes over transparent areas… if you were to hide the stencil layer, you’d see the color bourn layer over the whole comp (assuming it was a comprised layer). so the edges of the branches that are slightly transparent are now getting treated a little differently by the color burn layer.

    what you can trying is not using the stencil layer, and instead, click the mysterious ‘T’ option just to the right of the blending mode of the color burn layer. this will clip that layer to the alpha transparency of all layers bellow it, and i think it should work for you.

    if not, you may be able to simply add the fractal noise effect to the branches and use the blending mode setting within the effect to blend it with the original image.

    Kevin Camp
    Art Director
    KCPQ, KZJO & KRCW

  • Darby Edelen

    April 2, 2017 at 9:54 pm

    My suggestion is to keep the top layer set to stencil alpha and apply a Shift Channels effect to the lower layer and set Alpha to Full On.

    Even the Preserve Transparency switch can leave color fringes.

    Darby Edelen

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