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Old August 9th, 2010, 12:37 PM   #1
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How do I get a better green screen key with Keylight?

I'm using Keylight 1.2 in After Effects to key out a green screen for an interview subject.

My general workflow is:

1. Create a mask around the subject.
2. Select the screen color close to the subject's face.
3. Change View to "Screen Matte"
4. Adjust clip black to get rid of the gray in the black area.
5. Adjust clip white to get rid of the black in the white area.
6. Adjust screen shrink/grow to get rid of any lines around the subject.

My problem is that, while the key itself doesn't look too bad, I get blackish artifacts on the subject, and when I play the video, it sort of has that analog-fuzzy look that moves. This occurs over the entire subject, not just the face or his/her clothes. I don't know what this effect is called, but is there something I am doing or not doing that would explain this issue? I repeatedly have this problem even when working with different subjects wearing different colors (obviously not green).

If people need to see this, I can export a clip and provide a link to it but I've seen this type of problem in many videos that use keyed backgrounds so I assume it's a common problem with a specific solution.
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Old August 9th, 2010, 12:56 PM   #2
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My first guess is that you have taken one or both of the clips settings to far.
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Old August 10th, 2010, 09:05 AM   #3
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These artifacts actually appear right after choosing the screen color. I have a feeling I'm missing a detail that make make a much more natural subject after keying the background.
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Old August 10th, 2010, 09:27 AM   #4
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Have you been to videocopilot.net?? They have a great tutorial for this

VIDEO COPILOT | After Effects Tutorials, Plug-ins and Stock Footage for Post Production Professionals

VIDEO COPILOT | After Effects Tutorials, Plug-ins and Stock Footage for Post Production Professionals
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Old August 10th, 2010, 11:20 PM   #5
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Quote:
Originally Posted by Natan Pakman View Post
These artifacts actually appear right after choosing the screen color. I have a feeling I'm missing a detail that make make a much more natural subject after keying the background.
Can you restate please? I'm assuming that if you use Keylight and just pick the color (without doing anything else), you STILL get the artifacts?

If this is so, then try to create a test mask around a patch over where this is happening, and see if the area is still being affected after keylight is processed.

Is this happening for all your green screen shots? Green spill won't account for random black artifacts. Put a white matt under the green screen plate and see if the black artifacts are turning white. If so, there are green elements in your footage that you need to mask out. If you post a sample of the video, I might be able to check things out further.
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Old August 17th, 2010, 03:55 AM   #6
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You can find replace colour option under the ScreenMatte, try change the replace method to Hard Colour
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Old August 24th, 2010, 02:18 AM   #7
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How did you shoot this?

What was the format? Was in-camera sharpening turned off? What was the green screen's exposure set at?

I posted several messages on this board that outline how I shoot green screen, and I'm able to key hair, veils and translucent plastic. The important elements include shooting in HD, turning off any sharpening in the camera, and getting the green screen at 50 IRE. Also important to color balance for the light that's illuminating the green screen.
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