jarmo
New Member
Posts: 15
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Post by jarmo on Sept 23, 2004 12:08:24 GMT -8
In addition to not using blue clothing in the blue screen stage (or green clothing on the green screen stage), keep in mind white clothing too. It easily reflects blue or green from the sides - almost acts as a bounch board.
Keep your subject as far as possible away from the blue or green screen, or learn to isolate them with flags.
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jarmo
New Member
Posts: 15
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Post by jarmo on Sept 29, 2004 18:04:36 GMT -8
Yeah, black too (I think) tends to absorb spill from a set
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Post by Vince De Quattro on Sept 30, 2004 16:07:53 GMT -8
no matter what type of clothing you put on your talent, you will get some form of matte spill in the FG. so just use my nifty little filter to neutralize its effect:
(in a pixel math operand for a given image pixel)
r = r g = g b = (b>g) * g + (b>=g) * b
means
if the blue component of the color array <r,g,b> for any pixel is greater than the green component, use the green component value for blue, otherwise use the blue component.
for green screen work, switch green for blue
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Post by Vince De Quattro on Nov 5, 2004 0:11:13 GMT -8
Yes, I'd like to learn how to do keying correctly. I know the basics of edge thin, tolerance, garbage matte, etc. but I'd love to see how you do it and in which order. Maybe you could show me showtime during workshop time. Jarmo Some basics for a good blue/green screen extraction (1) set up an evenly lit, high chroma screen. be sure to avoid shadows falling onto the surface. the best blue/green screens are those that are luminant. (2) beware reflective clothing, blondes, chroma-matching clothing, glasses. (3) beware absorbtive clothing, black leather, black sweaters, etc. (4) be sure that your subjects don't break frame (unless called for in the script) (5) try to shoot progressive dv 24p/30p in order to avoid interlacing artifacts (6) decrease your key to fill ratio slightly to suppress spill and yet retain contrast (7) use additional rim lights to add light wrap on your subjects. it will help with edges later. try gelling these special rim lights with a complimentary screening color (like magenta for green and orange for blue).
Post-production (Compositing) Solutions (1) you may want to separate your extraction into two passes, one hard extraction for the interior to fight drop outs and one soft extraction to preserve the edges. (2) spill suppress the heck out of it (3) edgeblend it (4) edgewrap it in the high value areas of the comp (5) edgeblur it if necessary (6) do your fg color correction after the extraction
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