Shooting on a Blue Screen Question

[Anthony_Gilmore]

I've been shooting in 24PA and would like to incorporate some blue screen shots. Is it ok to shoot these in the same 24PA setting? thanks

[Barry_Green]

Yes, 24PA is fine for blue/greenscreen. Some of the best keys we've pulled from DV footage has come from 24PA mode. Not that it makes a big difference, because the 4:1:1 chroma issue is still there, but it just seems a little easier to pull keys without having to deal with interlace/comb artifacts.

[Anthony_Gilmore]

barry,

thanks for the quick answer. one thing...and sorry this sounds idiotic...what is the 4:1:1 chroma issue?

[Barry_Green]

DV doesn't record as much color information as other formats do -- it records only one color sample for every four luminance samples, for example. That can make for some blocky footage.

Look at this page for some examples of how 4:1:1 compares to 4:2:0 (NTSC vs. PAL, effectively) and then how cleanly 4:2:2 samples color. With 4:1:1 or 4:2:0, chroma keying will be difficult.
http://www.eleventy.org/dv-en/

[jmproductions13]

many editing programs have a filter you can apply to adjust for this. i use final cut pro and appling the filter before exporting image sequences has greatly improved my keys