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  • #202927

    Hi Ron,
    Well nowdays my eyes are always on your “The Art and Science of Digital Compositing” .Well in the matt creation chapter there is a piece of technique

    as you said ” Assume we are working with an image shot on a blue background. The first step the color difference method involves the creation of a new image in which this blue backing is suppressed to black. This is done by selectively substituting the green channel for the blue channel in every pixel in which the existing blue component has a greater intensity than the green component. In other words, for each pixel,

    If Blue > Green
    then New blue = Green
    else New blue = Blue “

    so you is telling to substitute the green channel for the blue channel and then put a condition. I tried a lot to do this in nuke. But ended scratching my head.So please give me a script or something to demonstrate this or anything which can clear my mind.Thanks



    i don’t know nuke(yet)

    but in terms of logic ops i think its something like this…

    perform a MAX on the red and green then (SUBTRACT) this value from blue. you will then need to invert to get the matte.

    if it was a green greenscreen then swap the blue and green nodes in the above.


    thanks p gill.i will try that

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