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Thread: CHROMA KEY

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    Member John Grow's Avatar
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    CHROMA KEY

    Does anyone here shoot against choma key?

    I am having some issues that look like light is reflecting off the backdrop and onto the person. I am trying to use this technique for simpler knockout, but the fringing from the reflections are killing me.

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    Re: CHROMA KEY

    Precisely why I stopped using it myself. One way to mitigate the problem is to place flags or light sinks between the subject and background, but just out of frame. I will reduce some of the scatter that creates the fringing, but not eliminate it completely. Another thing to watch is the reflected light from the chromakey backgrounds bouncing off a light ceiling and other objects, creating a color cast that is not pretty.

    I like the concept for knocking things out, but in actual practice, it has its problems. The only other suggestion if you want to keep using the background is to create a lot more separation from your subject, and not just having it placed behind them. In other words, place the subject a good 5-7 feet or more in front of the chromakey background, light the background with controlled light to prevent it blowing out too much, and shooting your subject with a longer lens to flatten the perspective a bit more. Sometimes that works.

    LJ

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    Member John Grow's Avatar
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    Re: CHROMA KEY

    Thanks for the help. I thought this would be an easier extraction but it was not. I though that having 2-3 feet from the B/G would be good enough, but apparently not. I thought what someone would offer a "flatter" chroma key B/G that wouldn't splatter so much light.

    I have to find a better way to do this.

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    Re: CHROMA KEY

    John,
    A lot depends on how the B/G is lit. For example, if you used something like a strip light from above, the reflections off of the B/G, may not hit the subject quite as much as ones bouncing straight back from more frontal lighting of the B/G. I do think getting more separation between the subject and the separately lit B/G will improve things quite a bit. Worth giving it a try. My suggestion to use a longer lens and shoot further way is to make sure your framing will still contain the B/G to the edges, so that you can mask things off easily. If you are doing headshots, this is relatively easy. As the coverage increases to waist and up, then small group or full body, you start running into more trouble and a greater need to be further away from subject. However keeping the separation between the subject and the B/G is important, and I would try lighting the B/G with a downward angling light to minimize reflections toward the subject.

    LJ

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    Member John Grow's Avatar
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    Re: CHROMA KEY

    Thanks

    I will have another shot at this early next week when I start the next round of execs.

    On a side note: I found a way in PS to COMPLETELY remove the fringing and it would have saved me grief had I found it sooner.

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    Re: CHROMA KEY

    Quote Originally Posted by John Grow View Post
    Thanks

    On a side note: I found a way in PS to COMPLETELY remove the fringing and it would have saved me grief had I found it sooner.
    John,

    Could you share this technique with the rest of us?

    Cheers,
    Kumar

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