Thread: Shooting Chroma Key with RED-One ??

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  1. #1 Shooting Chroma Key with RED-One ?? 
    Senior Member George D.'s Avatar
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    We will be purchasing a new RED-One in March, but in the meantime I'd like to know what you guys recommend is the best color (blue or green) for backgrounds when shooting Chroma Key affects with the RED-One, then later compositing with Adobe CS5?

    Most of the backgrounds we will be matting in will be of outdoor scenics, etc, involving a lot of green trees, plants, grass, etc., so my tendency is to go with blue so the matte does not get polluted. Is there a problem with that, or what do you advise?

    Thanks, and have a wonderful New Year.
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  2. #2  
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    The RED MX works WONDERFUL for green and blue screen.
    You can get very nice results with the original RED M but the MX is just so clean and allows me to shoot with less light so I prefer the MX by far over any other camera out in the market. Until the Epic is available to the masses this will be the way to shoot.

    Some things to remember.
    Daylight results in a nicer image than tungsten.
    You dont have to shoot daylight but if you can introduce some blue gel light youll have a nicer result.

    Another thing is even lighting on the green of course is helpful.

    NUKE and AE both give fantastic results working with the RAW or transcoded files to PR 4x4 and even DPX or TIFF ive done them all and been very please with all the results.
    Some are easier to work with than others depending on your budget and workflow.

    I prefer to shoot green screen over blue screen but they both work nicely.

    Ive worked a television series 4 months all green screen and a feature all green screen.
    both were completely different work flows
    one was Nuke the other was CS4
    several music videos and infomercials

    so if you have any more questions ill do what i can to give you a hand
    best of luck

    Luis
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  3. #3  
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    Quote Originally Posted by George D. View Post
    We will be purchasing a new RED-One in March, but in the meantime I'd like to know what you guys recommend is the best color (blue or green) for backgrounds when shooting Chroma Key affects with the RED-One, then later compositing with Adobe CS5?

    Most of the backgrounds we will be matting in will be of outdoor scenics, etc, involving a lot of green trees, plants, grass, etc., so my tendency is to go with blue so the matte does not get polluted. Is there a problem with that, or what do you advise?
    You just answered your own question. If you're shooting green objects and surroundings, use a blue screen and talk to wardrobe during preproduction to make sure you don't get boned by blue clothing.
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  4. #4  
    Senior Member Keith Nealy's Avatar
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    If your foreground objects are green like trees and grass, you need to use blue. I just finished a four commercial campaign that all took place in the jungle with waterfalls, leaves, grasses, etc. We shot everything on blue with green screen for our talent. We also shot isolated jungle elements in the jungle and used different kinds of matting and keys to isolate them into elements.

    Keylight in AE is far superior for keying than anything in Premiere. Take the time to learn the nuance of all the tools - it will pay off in clean keys.

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  5. #5  
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    Use the opposite color to the subject you are shooting in front of the screen (the background you will sub in is irrelevant). For example, I had to shoot toy army men which were mostly olive-drab. I used red poster board from an arts store and the key was ridiculously easy to pull.

    The things that really help with keying is to make sure the background is evenly lit (around 1 stop below the subject) and that your subject's edges are sharp. This includes motion blur. For example, I had to shoot the falling toy soldiers at a very low shutter then add the motion blur in post.

    If I understand it right the blue screen developed because of chemistry related to the film development process while green was logical as it is the actual color channel that is furthest away from skin tones. (Bayer sensors actually have 2 green receptors for every one red and blue - ask Graeme if this helps). Modern keying algorithms do not know green or blue, they are designed to do their math on any key color. The reason the Red One (and subsequent Red cams) do such a good job keying is two fold: 10 Bit per pixel and no color sharing between pixels. For this reason I personally do not see the need for expensive calibrated chroma paints or fabrics while the are absolutely essential for lesser video cameras. (I'm sure there are people who will disagree with me on this.)

    What the keying does is compare the RGB values pixel by pixel to your target key color to determine what the alpha value (transparency) of that pixel should be. This is overly simplified and there are many techniques for applying keying technologies. The color under the pixel (when 'stacked' in AE) is unknown and irrelevant to this process. Do some research on alpha channel and you'll better understand the issues at hand.

    Bob
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  6. #6  
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    When you say the trees will be matted in, it sounds like you mean that those are not your subjects. If this is correct, then do not worry about the background. The foreground is where you need to pull the key. Like what Mr. Gruen said, the sensor in the Red camera is a single bayer pattern sensor (contrary to 3 chip cameras). The bayer array takes advantage of the fact that most Luminance information is in the green channel. Shoot green screen for digital cameras unless your subjects on the screen are green themselves.
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