Pixel on Pixel Deletion

[Kevin Camp]

the effect you described is called difference matte, in the keying effects. apply it to the layer you want to key, then, within the effect, select the layer that you want to use as the difference layer. the effect will then compare the pixels from the two layers and try to remove the similar pixels. there are also settings for tolerance, softness and blur before difference.

there can be problems with this effect if the footage is not good. things like video noise or compression artifacts can be problematic, just to warn you….

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW

[Scydow Cross]

Ok thanks, but it isn’t really working.
I got a still image as my background, and the exact same background with me moving in the front.
Then I used the Difference Matte.
But I don’t seem to be able to get the background away (Matching Softness = 0.5% and the other one’s at 0%) Gets me the best effect, which is really bad.
How can I get the best effect?

[Kevin Camp]

using difference matte is not the optimal way to pull a key… noise and compression artifacts in either of the pieces of footage will make it hard to get good results and that’s excluding other issues, like a camera not being locked down well enough or the background changing slightly (like if the shot was outdoors and there was a slight breeze moving trees in the background)…

what you might try…

1. bring both pieces of footage into the same comp and hide the clean shot (the one with out you in the shot).

2. create a junk matte on the footage with you in the shot using a mask. try to keep it reasonably close to the subject (you) and animate the mask shape, keyframing each shape about every second at first, then add keyframes as needed.

3. when you are done with animating the mask, hit ‘mm’ (that’s 2 m’s) and adjust the feather property a little to soften the edges.

4. apply the difference matte to the footage with you in it and set the difference layer to the clean background. adjust the tolerance and softness.

5. you will probably need to go back and refine the junk matte, or take this comp into a new comp an do some rotoscoping to clean it up.

there are several good tutorials that discuss some methods of rotoscoping in the cow’s ae tutorials if you need help with that. just search the tutorials page for rotoscoping.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW

[Clyde Villegas]

How do I keyframe the mask position? I think masks has no position settings. What I’m doing now is highlighting all the points of the mask, moving all of them together at one time by dragging, and creating a keyframe in the “shape” setting/ effect (whatever it’s called). Am I doing it correctly? Thanks and God bless.

[Clyde Villegas]

Thanks Dave!