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Chroma key / blue screen


J Costantini

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Hi.

I would like to hear from you about shooting chroma key scenes using blue screens, please.

 

Any tips on lighting? Advices? or precautions to take?

Should I backlight the actors a lot, a few?

 

what IRE value should I have for the blue screen? should I overexpose it?

 

What should one do to avoid the blue on the actors' clothes and faces? (that "glow" around their hairs, etc)

 

is it a problem to have the blue area to be cut out of focus?

 

Any help is appreciated in order to cut the subject better in post, thanks.

 

PS: we're using a dsr-390

Edited by nillo
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Hi,

 

Because the green RGB channel makes proportionally the largest contribution to the luminance YUV channel, which is not subsampled. When the YUV data is transformed back to RGB (which will typically happen before the keyer sees it), the green channel has slightly higher resolution.

 

Phil

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Hi,

 

Because the green RGB channel makes proportionally the largest contribution to the luminance YUV channel, which is not subsampled. When the YUV data is transformed back to RGB (which will typically happen before the keyer sees it), the green channel has slightly higher resolution.

 

Phil

 

Phil,

 

Helpful answer, but I have noticed more 'detail black edges' on green v blue.

When I have tested both green + Blue , I don't see a big diference in the composite.

 

Thanks in advance

 

Stephen Williams DP

 

www.stephenw.com

 

Stephen

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My company does a ton of chroma screen composites (like average 10 per week) and if there was extraneous factor to choose either blue or green I'd choose green because I find it contaminates the shadows less - or at least the keyer is more forgiving for it. This is all HD though.

 

Just my humble two cents.

 

But also DV for keying.... ugh.

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My company does a ton of chroma screen composites (like average 10 per week) and if there was extraneous factor to choose either blue or green I'd choose green because I find it contaminates the shadows less - or at least the keyer is more forgiving for it.  This is all HD though.

 

Just my humble two cents.

 

But also DV for keying.... ugh.

 

 

Hi,

 

Very interesting.

Do you soften the edges and loose hair detail to improve the key?

IMHO the color of the background in the composite is quite important. I would not wan't to use a green screen if the final composite is against a blue sky.

 

 

Stephen Williams DP

 

www.stephenw.com

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