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Chroma Key RGB Value

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Seth Burke
Chroma Key RGB Value
on Jul 9, 2010 at 9:34:52 pm

Going to shoot a short spot with a person talking straight to camera with a TV behind her. The camera will be doing some slow dolly moves, nothing too big.

I need to generate a blue color and feed it to the TV Screen via DVI>HDMI from a Computer.

What is the correct/best RGB values to generate this in Photoshop?

We just need an image of a clean blue image that we can feed the TV. Shooting on Red, working with ProRes 444.

Been searching the net, can't seem to find an answer.

Thanks


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Dave LaRonde
Re: Chroma Key RGB Value
on Jul 9, 2010 at 10:03:18 pm

Most TV sets I've seen in the last several years automatically put up a blue screen when there's no signal coming in. Pretty easy, and it's a good blue. Test it on the TV set to be used during the shoot.

How do you plan to track the screen to keep the replacement footage in place?

How do you plan to deal with light glares when you dolly?

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Seth Burke
Re: Chroma Key RGB Value
on Jul 9, 2010 at 10:09:37 pm

Good question, I believe the screen that we're using has is an anti glare HDTV.

Most of the shots we're using will have elements within the frame that we can use to track. The screen will not leave the frame or anything.

But, isn't there a numerical RGB value that is best suited for keying? Particularly with After Effects?


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Dave LaRonde
Re: Chroma Key RGB Value
on Jul 9, 2010 at 10:16:50 pm

As long as you have a consistent color that doesn't show up anywhere else in the shot, you can pull a chroma key. You can also use garbage mattes to limit the area of the key. Pure colors work best, and the blue from an "I can't find any signal" TV set is pretty darn close blue.

Just set up the TV, yank the connectors off, shoot the blue TV screen on your camera and run a test chroma key.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Bill Kelly
Re: Chroma Key RGB Value
on Jul 10, 2010 at 1:23:47 am

The colors best suited and most used for keying are the pure colors. If you're using blue, the RGB values would be:

R - 0
G - 0
B - 255

If green screen then:

R - 0
G - 255
B - 0



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Stuart Robertson
Re: Chroma Key RGB Value
on Feb 24, 2012 at 10:12:36 pm

I'm going to disagree with all of you here. Although a "perfect"(0,255,0) greenscreen makes it easy to pull a hard-edged matte, the extreme luminance in the green channel will overwhelm the subtle edge details from your original photography, and the absence of any red or blue component in the fringe areas (hair, blur) will really mess you up when it comes to neutralizing the green spill. Based on experience, I'd recommend shooting greenscreens with a camera/light setting that results in a green area reading around 25,130,10 , and 30,70,160 for shooting a bluescreen.


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