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Chroma key / blue screen


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#1 J Costantini

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Posted 02 June 2005 - 11:22 PM

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, 02 June 2005 - 11:28 PM.

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#2 Landon D. Parks

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Posted 03 June 2005 - 01:49 AM

CLICK HERE! to go to another thread here on chroma key. Where I posted a diagram of how I lit a bluescreen interview a few years back.

Don't know if it will help, but it may.

Good luck with your project.
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#3 Preston Herrick

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Posted 03 June 2005 - 01:26 PM

You might also get better results pulling a key shooting greenscreen in conjunction with DVCAM rather than blue.
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#4 Stephen Williams

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Posted 03 June 2005 - 02:09 PM

You might also get better results pulling a key shooting greenscreen in conjunction with DVCAM rather than blue.

<{POST_SNAPBACK}>


Hi,

Why is that?

Stephen
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#5 Phil Rhodes

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Posted 03 June 2005 - 05:13 PM

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.

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#6 Stephen Williams

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Posted 04 June 2005 - 03:19 AM

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

<{POST_SNAPBACK}>


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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#7 Mark Allen

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Posted 04 June 2005 - 03:37 AM

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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#8 Stephen Williams

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Posted 04 June 2005 - 04:03 AM

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.

<{POST_SNAPBACK}>



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

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