Hard Shadows

by Dyske Suematsu  •  October 5, 2006

Try to avoid any situations where the foreground subject touches the green element. If this is unavoidable (and it often is), try to minimize the amount of shadow the foreground casts on the green element. Or, try not to move the foreground subject. Hard shadows are problematic because it is impossible to tell where the green ends and the shape of the subject begins. So, the keyer has no choice but to outline the edges of the shadow. In video (as well as in film), the darker the area, the noisier it is. Because of this, the edges around the shadow vibrates significantly. See the QuickTime movie below.

Exhibit A

In the Exhibit B below, there are hard shadows between the actors and the benches they are sitting on, but this is not a problem because the parts of them that are touching the benches (their asses) do not move. So, I can manually draw a static mask to remove the benches for the entire duration of the scene, thereby eliminating the hard shadow areas that would otherwise vibrate.

Exhibit B

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