Using White or Green screen for aplha - for mass images

Discussion in 'Digital Darkroom' started by jpuckett, Jul 31, 2008.

  1. I shoot youth sports photography and was thinking of using green or white backgrounds so I could key out the
    individual portraits and drop into a template background.

    Has anyone found a fairly easy way of separating the subject from green/white keys to a new background and not
    having green color/white color or artifacts in the hair. Or a technique to quickly remove and/or correct hair issues.

    Reason is I process about 150 individual portrait images a week and to have to spend time removing left over
    artifacts or color correcting hair for that many is... a bit more than I wish to spend.
  2. A green screen will do a better job than white. As the light level increases everything becomes white. For example hair is tough to separate because the highlights you want to keep are almost white. Have you ever seen a purple specular highlight? No they are white. You can easily get a background in a green made for this purpose.

    Good luck

  3. "...and not having green color/white color or artifacts in the hair."

    green screen should be 1.5 stops under from your key light.
  4. [​IMG]

    For video, we set the key and the green screen at the same stop. It's very imporant to make sure the background it lit evenly, so we run a light meter back and forth across the greenscreen. On a large stage, specialized lighting instruments are used to get even illumination. On smaller shoots, KinoFlo's are the standard. From the snapshot above, you can see how evenly the background is lit. It take a lot of light to do that. There is also a huge soft source overhead that provides the key. The "china ball" on a pole gives a little fill.

    Make sure you separate your subject from the background several feet to avoid spill, and to throw the green screen out of focus.

    Do not use magenta (anti-green) gels on your hairlight, as some suggest, to separate your subject-- it causes a hard line around the edge. Watch for stray hairs, and use hairspray, if necessary and possible-- this is a lot easier on a video monitor, but do the best you can. Stray hairs, and areas where you see through hair wisps, are what will kill you in post. It also can't hurt to use the best plug-in available to create the matte.

    There's lots of information about greenscreen shooting online, but most of the good info will be in film and video forums, as this is where the vast majority of matte work is done.
  5. Thanks for all of your suggestions. Any suggestions on which product works best manuf. for 9ftw. I would think
    muslim is a definite no no. And I agree Damon I do foresee many flyaway hairs with that many kids at least 50% will
    have very curly or flyaway hair and too spray them all down would grind shooting to a crawl. I guess the thing to
    do is test it and see.
  6. Give it a try. Have your subjects smooth or comb their hair a little. I figured hairspray would be out of the question. Paint the back of some scrap vinyl flooring or get some fabric. Modern green screens use what's called Digital Green, which to my eye looks like there's a little yellow in there. I think for your use, as long as it's solid, flat and and can be lit evenly (and nobody will be wearing that color) it would work.

    Avoid spill from the background, and the wraparound effect from a large soft source will help fill the nooks and crannies. My experience is with video, but my best guess is that crisp focus, strobe lights, and the much higher resolution of a dslr compared to video would isolate strays and make them easier to correct/defringe. A blurry or soft photo would make for foreground colors that are contaminated with the background.

    If it doesn't work out, you can always use a backdrop.
  7. Thanks for all of your suggestions. I will test it and see if it is worth it...I might have to stick with the backdrop.


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