How do I properly use core matte to keep green section of shirt on using green screen keying?


I have some footage shot with a green screen and stupid me didn’t pay attention to the shirt I had on which on the center of the shirt has some green. So naturally, I have a hole in my chest when keying. My solution was to create a mask around it and then feed it to the “core matte” input on the keying node. While this does work, it changes the color of the part on my shirt from green to a blueish color.

My questions are, is this the correct way to fix this? If it is, how do I prevent the color change and if it is not, what would be the best solution?

Thank you so much in advance for taking the time to help!

I don’t know why it does that, but an easy way around it is to just combine the mask with the matte output and use that to set the alpha channel of the footage:

keying.blend (1004.2 KB)

This looks perfect! Thank you so much for the detailed response. I will try this out when i get home from work.

I wonder if this is something we should report as a bug or if it is actually working as intended.

I’m not sure if it works as it is supposed to, but it acts the same way in 2.79. Try filing a bug report. It could just be a long standing glitch.

So I had to do it a little differently but never would have thought of it without your answer. Your solution worked, but brought out the imperfection in my footage. For some reason, I had extra green showing up outside of the mask. I wound up putting the mask directly to the set alpha node as the alpha input and putting the original movie clip to the image input. The resulting image from that is just the mask alpha channel. Then I just used an alpha over to combine it with the keyed footage to add the part back that I needed. Here are some screen shots.

Here is just the section i masked out to add back in…

Now to animate the mask to follow me! Thanks again for the help, once I create a bug report, I’ll post it back here so you can see if you’re interested.