Posted by PTravel on 09/11/06 18:55

good grief -- I don't know what happened, but this is rife with typos. I'll
fix the whole thing:


> Okay, here's how I handle keying out material that hasn't been
> specifically prepared for keying. I'll explain this by example, because I
> think it's clearer.
>
> Imagine a black box on a white background. The center of the black box is
> white.
>
> Obviously, if I use a luma or color key to key out the background, I'll
> also lose the center of the box, which I don't want to do.
>
> So, I create a garbage matte that covers, roughly, the center of the box.
> I either pin it to the center so that it tracks movement automatically, or
> I use key frames and manually track. It doesn't have to be exact -- it
> just needs to cover up that which I don't want keyed out.
>
> I then apply my luminance (or color key) and key out the background BUT I
> reverse the key, i.e. everything but the background gets keyed out. I've
> now created a matte the eliminates, exactly, the background and only the
> background.
>
> I change the color of the matte to green and super it over the original
> clip. Using my box example, I now a black box with a white center and a
> green background.
>
> NOW I can use chromakeying to alpha out the green background.
>
> I find this works pretty well.
>

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