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Old August 25th, 2009, 10:30 AM   #1
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Decrease yellow cast without a DSC chart

I have a GY-HD100, and am using Paolo's True Color 3 setup, with no modifications. I have noticed with the TC3 settings that I am getting a persistent, slight yellow cast, especially with green foliage in the background, but also with skin tones. (Think old Super 8 Ektachrome, and you'll know exactly what I mean.)

I can restore it pretty successfully using the Color Correction filter in Vegas 8.0 by bumping the Mid tones toward Cyan/Blue (Angle: 304.5, Magnitude: .229 on the middle color wheel). However, I'd like to tweak the camera settings a bit so I don't have to color correct everything I shoot with this camera.

I've read Paolo's discussion about tweaking these settings with a DSC Color Chart, but I do not have access to such a chart. I do have HDV Rack, so do have access to a vectorscope. I have read the forums and the JVC manual about color Gain and Rotation in the Color Matrix Adjust menu, and frankly, my head is swimming. If I want to REDUCE yellow, it seems I should nudge the Blue Gain UP a bit. But, according to the manual, this will also bump up the Yellow, which is exactly what I don't want.

I thought about shooting a NTSC test pattern from a calibrated LCD monitor, and using that to judge the color accuracy. Will this work? Any other suggestions -- especially for those of us on a limited budget -- will be greatly appreciated.
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Old August 27th, 2009, 10:27 AM   #2
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Can anyone help?
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Old August 27th, 2009, 01:22 PM   #3
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Without a DSC chart it will be very hard to calibrate/adjust your setting.
The LCD monitor will be no real alternative.
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Old August 29th, 2009, 12:30 AM   #4
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OK, I figured out a solution. I hooked the HD100 up to my laptop with HDV Rack. On my desktop machine, in Vegas 8.0, I set the preview monitor to OHCI DV output through my DV deck and to my calibrated CRT monitor. Then I aimed the camera at the CRT screen and used the variable shutter to minimize the rolling bar.

I put a white solid on the Vegas timeline and got a manual white balance in the camera. Then I put a NTSC color bar chart on the timeline and shot that. I compared the HDV Rack Vectorscope reading from shooting the Vegas NTSC color bars with the HD 100's internal color bars and with HDV Rack's internal color bars.

Starting with Paolo's TruColor 3 settings, I then adjusted the Red Gain, Green Gain and Blue Gain in the HD100 Color Matrix until it was as close to the vectorscope readings for the internal HD100 color bars as I could get. Shooting off a CRT screen meant the vectorscope readings fluctuated a bit, but they were steady enough to get a decent reading.

I kept my fingers crossed, but after shooting today, I'm happy to report that my uncorrected images look much better, good neutral color, with no yellow bias.

Just thought I'd post in case there was someone else looking for a way to tweak the color calibration a bit without a DSC color chart. Probably not a perfect solution, but it appeared to work well enough.
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Last edited by Brian Standing; August 29th, 2009 at 12:33 AM. Reason: Added info
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Old August 29th, 2009, 04:50 PM   #5
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Here are the color matrix settings I came up with:

R GAIN: -1
R ROTATION: 4
G GAIN: 1
G ROTATION: NORMAL
B GAIN: 3
B ROTATION: -3

Hope this helps someone.
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