user8064: I have two (rgb) jpeg sequences one with the alpha information (black and white) the other one with the green screen footage. I keyed them with Keylight and they look perfect in AE before exporting.

When I import the jpeg sequences back in AE and apply the alpha, I get a green hallow.

It seems to be some premultiplication issue. What did I do wrong exporting / importing the jpeg sequences?



user2836: Part of it may be the fact you are using JPEG sequences.  JPEG isn't a pixel accurate format and you are going to have some differences in block quantization that could potentially result in mismatches.
I don't think that is the only issue since it is a bit too regular for it to be the only issue, but I'd try to use an intermediate format that is a bit more lossless for doing things that need to be pixel accurate match up.

user8064: The problem is that my alpha Mask has a feather. Which results in greeen peaking through the Mask. So the only solutions are export an alpha mask with no feather or export the original image with a black or desaturated background.


8064: <p>I have two (rgb) jpeg sequences one with the alpha information (black and white) the other one with the green screen footage. I keyed them with Keylight and they look perfect in AE before exporting.</p>

<p><img src="https://i.stack.imgur.com/VMFA8.png" alt="key"></p>

<p>When I import the jpeg sequences back in AE and apply the alpha, I get a green hallow.</p>

<p><img src="https://i.stack.imgur.com/Wwa89.png" alt="premult"></p>

<p>It seems to be some premultiplication issue. What did I do wrong exporting / importing the jpeg sequences?</p>

<p><img src="https://i.stack.imgur.com/tRnCV.jpg" alt="greenscreen">
<img src="https://i.stack.imgur.com/Vi6eM.jpg" alt="alpha"></p>
 2836: <p>Part of it may be the fact you are using JPEG sequences.  JPEG isn't a pixel accurate format and you are going to have some differences in block quantization that could potentially result in mismatches.</p>

<p>I don't think that is the only issue since it is a bit too regular for it to be the only issue, but I'd try to use an intermediate format that is a bit more lossless for doing things that need to be pixel accurate match up.</p>
 8064: <p>The problem is that my alpha Mask has a feather. Which results in greeen peaking through the Mask. So the only solutions are export an alpha mask with no feather or export the original image with a black or desaturated background.</p>

<p><img src="https://i.stack.imgur.com/iLSod.png" alt="Feather"></p>
