From the course: After Effects Compositing: 1 Intro to VFX

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Prevent alpha channel fringing

Prevent alpha channel fringing - After Effects Tutorial

From the course: After Effects Compositing: 1 Intro to VFX

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Prevent alpha channel fringing

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- So as I said, if your selections are generated by the computer, there's one thing that can come up, which has to do with alpha channel premultiplication. Now, that's a very complicated way of saying fringing. And so if you ever see a foreground come in with black fringes around the edges, you know that you have a premultiplication problem. This text was created in Photoshop and here you can see a transparency layer. So with a transparency layer, there's not going to be any background mixed into the foreground. It's often the case, however, that you don't work with transparency data, but instead with an alpha channel. Now, if I go into Interpret Footage, Main, I can ignore the alpha channel that's in this TIFF image. And now you can see that everything looks just fine. There's nice feathering of the edges against the background, but of course we don't have a selection anymore. If I go to the alpha channel, you can see it's just turned off. So, instead what we want to do is go into…

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