Chroma key changes overlay subject color - remedy?

mtnmiller wrote on 7/25/2008, 12:57 PM
I've got a clip of a hot air balloon floating through the air, and am keying out the blue of the sky behind it.

There is also some blue in the color of the balloon that's much darker than that of the sky. But when I key out the sky, the blue in the balloon turns green.

Why is this?
Any ideas on how to keep the balloon from changing color?

Thanks for any help

Comments

richard-courtney wrote on 7/25/2008, 7:46 PM
In the chroma key fx,
first click on eyedropper to select the sky color
then click on "show mask only".

Check mask. Should be white and black only. Any grey areas need to be
adjusted out using the low and high threshold sliders
JackW wrote on 7/25/2008, 10:40 PM
When you key out blue, some of the blue in the balloon panel is being keyed out as well, leaving behind the greens in the blue panel of the balloon.

Since the blue in the sky is undoubtedly made up of more than one value I'd hold down the mouse key and drag the eye dropper in order to get a range of color. You may have to do several keys, too, to get rid of just the colors you want. It's gonna take some experimentation.

Using the slider adjustments, as suggested, will enable you to do this in a fairly subtle manner.

Jack
Widetrack wrote on 7/27/2008, 9:19 AM
Jack:

How do you do multiple keys on one Event? Make copies of the Event and key each one differently?

I created a problem by coming back to a green screen shoot after a break near the end of a long, exhausting shoot and didin't turn back on all the lights on the screen. In post, I find the color/lighting differences in the screen don't let me key the whole thing out.

Is there a way to fix this?