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A green screen question and suggestion...

Posted: Sun, 5th Sep 2004, 12:22pm

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CurtinParloe

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I was wondering about the reason for using greenscreen over bluescreen.

A lot of guys on here have said that camcorders store more information for the green segment of the image, which makes for a better key. I always understood that it was precisely the opposite, that red has the most information stored (presumably due to the amount of red found in skin pigment - you wouldn't try keying out the red for footage of a person, after all!), followed by blue, then green. This means that green is ideal to key out because the least amount of image quality is lost, and it's more forgiving of variations. Also, there is a lot of blue in natural light, which makes bluescreening much more unreliable outdoors.
Am I wrong?

Now to the suggestion. I've done a small screentest based on Dulux colour cards (the free ones you get from B and Q). The best shades I found for greenscreening were from the "Fresh" range:

Green Parrot 1 (50GY 39/536)
Green Parrot 2 (50GY 51/437)
Willow Creek 1 (30GY 40/531)
Willow Creek 2 (30GY 51/423)
Kiwi Burst 1 (10GY 41/600)
Kiwi Burst 2 (10GY 52/541)

I set the White adjustment to about 30 for the best results.
I haven't got anywhere to host the image yet, but I'll probably try next with tester pots to find the best colour. Stay tuned smile
Posted: Sun, 5th Sep 2004, 8:23pm

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Axeman

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As far as the information stored, you are kind of right from a certain viewpoint. Blue and green were originally used because they were the least common colors in fleshtones. Especially blue, because the yellow tones in skin are based in green for the purposes of film. On film there is no resolution or digital info regarding the color, which really seperates the entire process from how it is handled on video.

It is somewhat different on video, where all the color information is stored digitally. The argument for using green is basically that the camcorders have more space available to store green information than for any other color. In digital video all of the color info is compressed to save space; green therefor has to be compressed less, which means more of the original info is retained, hence the information in the green channel is the most precise and will give the best key.

The difference I guess is that you are thinking of what colors you see most in the image, whereas they are thinking of how the camera records the color data from a technical standpoint.

As far as the color samples, any really bright green should give you decent results. You might check you www.studiodepot.com or some other site that sells greenscreen material and paint just to get a good color to reference from. then compare the swatches you have to their green to see which is closest. Or print out the swatch from the website and have the paint store do a colormatch. One thing to keep in mind when using normal paint to make a greenscreen is that it will be subjected to very intense lighting (which produces a lot of heat), so make sure your paint will stand up to it.
Posted: Mon, 6th Sep 2004, 4:56am

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GeeksGoneBad

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Here's a guy talking about why green is better... Something to do with the Luminence channel too, not just the three colors...

http://dtvprofessional.com/articles/viewarticle.jsp?id=21452
Posted: Mon, 6th Sep 2004, 11:11am

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Arktic

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You might check you www.studiodepot.com or some other site that sells greenscreen material and paint just to get a good color to reference from. then compare the swatches you have to their green to see which is closest
Or you could try getting hold of a very small ammount of 'real' greenscreen material, and using Dulux's colour matching service to get the exact same colour for a lot less than real chromakey paint smile

Cheers,
Arktic