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Re: Why is colored stage lighting creating blotches of color on my PMW-EX1? Is it like color-overexposure or something?

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Stephen MayRe: Why is colored stage lighting creating blotches of color on my PMW-EX1? Is it like color-overexposure or something?
by on Feb 11, 2012 at 5:19:17 pm

David, XDCAM EX samples 4:2:0, which is shaving color information off in the acquisition. I'm not ranting, I have two EX1 cams and really appreciate their amazing versitility, etc. The sensors are 3 1/2" CMOS chips with a native resolution of 1920 x 1080, however, as I said, the information for red, and for blue is not at the same quality as green/luminance. I'm not an engineer, but in simple terms, your stage lighting scenario is a challenge in this sense, and a chroma sampling of 4:2:2 would produce better results.

But so far, I haven't said anything helpful, so here's some suggestions; if you haven't already tried this, tapping the HD-SDI output and recording the footage onto a AJA KiPro, or Convergent Design NanoFlash, or some type of HD-SDI flash recorder is a good way to improve the image, or if you're simply switching live, use the HD-SDI output to the switcher. If you're already doing that, you might consider using a picture profile where you reduce the chroma and to a degree, the contrast - record a "flatter" image, less punch. This will help acquire more informaion in the image and you can bump up your projectors in show to regain the punch, or for post delivery, use some amount of color correction to regain the punch of color and contrast. Some people use LUT's (look up tables) and later employ a curve - often called S-curve because the curve looks like an S where the blacks are crushed (a little) the mids are left alone, and the highs are bumped up again.

Obviously, converntional lighting has a different color temperature, and that would be optimal, but LED lighting is attractive to LD's for a bunch of reasons, and I am not sure how much push you have in changing the type of lighting your LD is using. I do a show that uses LED lighting and we shoot it with three XDCAM EX cameras and I did what I suggested to you but I am also part of the crew and was able to add some white convertional light on across the truss and just a little un-gelled lighting across the truss gave me a huge boost! That also brings up a final aspect of your situation, you are likely opening your iris to get as much light as you can muster, and also you might even be moving to +3db gain but hopefully not more. Adding just a small amount of un-gelled conventional light will help you to go to 0db gain and possibly close your iris back down a small bit and the green CMOS will be able to capture enough information for the 4:2:0 sampling to work better. I really hope this helps you, good luck!

Stephen

Stephen May
Keystone Media Productions
Freelance Videographer


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