Chromakey Lighting and/or Keylight Question
by Paul Gustafson
on
Aug 25, 2008 at 6:58:43 pm
Hi everyone. I'm a new user of AE and I am having a small issue with Keylight(I think). I videotaped a speaker on a greenscreen with a Sony PD170(I know, but I don't own an HD camera yet). The greenscreen keyed out nicely, but I am having an issue with some green/grey spill? in the armpit area of the subject that I can't get rid of. If I decrease the Shrink/Grow value to get rid of it, I end up shrinking too much of the subject. I tried using Aharon Rabinowitz's 'super tight junk matte' tutorial, but it didn't help much.
Is this because that area of the body needs more light or is there a setting in Keylight that I am missing? Thanks for any help.
Re: Chromakey Lighting and/or Keylight Question by Barend Onneweer on Aug 25, 2008 at 8:26:11 pm
The shrink/grow parameters won't do any good. You can get super-tight edges using it, (usually right where you don't want the edges to be tight), but it also cuts corners and removes any detail - right under the armpits for instance.
I'm guessing the problem is caused by the DV compression - since those sharp details suffer a lot from the compression. If you have Magic Bullet of Key Correct Pro (both sets are Red Giant Software) you could use the deartifactor that comes with those.
If not, try this:
Drag your source footage into a clean comp (call it Deartifact)
Duplicate it.
Apply a 4 pixel Median filter to the top layer.
Set top layer blend mode to 'color'.
The difference is very subtle, but you've essentially smoothed out the color pixellation caused by the DV compression.
Now drag this comp into a new comp and apply your keying.
If that doesn't help, you're probably best off animating a small mask to get rid of those areas.
Re: Chromakey Lighting and/or Keylight Question by Danny Hays on Aug 26, 2008 at 12:50:00 am
In ther future, It's best to put as much distance between the subject and the screen as possible and use some back lighting on the subject. This will greatly reduce the spill and make it easy for keying.
Danny Hays
