Hi there, when keying a series of green screen elements into a sequence of shots, should the elements be color matched and corrected before keying (for consistency but perhaps changing the green screen color) or after (when one can take a more global overview of the interplay of FG and BG for the whole sequence)?
Like Roland and Todd I key first and grade after. I normally use at least two passes- one on the individual layers to bring everything to similar values and then a overall grade on an Adjustment layer on top to blend all elements.
Thanks for the thoughts, I was confused by the elements I have because they are rather inconsistent (green screen color variations and the grading on the photographed content changes shot to shot) but seeing how my material “breaks down” a bit when color-corrected first then keyed I’m gonna do what you do: key first then use per-element CCs, then adjustment layers for overall shot CCs – cheers 🙂
IMO, color grading is the last step, but sometimes you need to do both, so before and after. I can’t say if that will work with every case, but the fact is, sometimes you get footage that unfortunately was not shot optimally.
I can remember a specific case where we had no choice but to adjust the color in order to get a better key. And on top of that, the method we ended up using was quite complex, where we only used the result as a matte, etc. etc. etc… which gave us slightly more options than you can achieve using the standard method. Then when we were happy with the result, we tweaked the colors again to better match the footage we were keying on top of.
So, to conclude, you cannot really color grade the footage before the key, because changes to that footage, will likely affect your key result