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Old November 3rd, 2006, 01:22 AM   #1
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Color Shift w/exposure change

I was trying to match 3 of the GY HD-100s in a multi-cam situation. Two things came up for me. One is that I couldn't find a way of balancing/painting blacks. One camera had excessive blues and reds in the blacks I couldn't get out- and using the White B and R paint screwed up the mid- and highlight parts of the image. Any ideas about how to paint blacks?

The other question, if I got 2 cameras to match and then changed the exposure by even a stop, the color balance changed all over the place.

I've engineered a lot of camera's in flypack situations, JVC's, Sonys, and Ikegamis. Mostly via CCU's but sometimes by camera menu and I've never seen anything like this before. Being new to the camera, I'm entirely open to the idea of 'operator error', but I need to know what, if anything, I did wrong, or if these cameras are different.

Also, the camera was off full auto, white balance was not on preset and I don''t believe that there were any scene files these cameras were cuing off of.
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Old November 3rd, 2006, 02:49 AM   #2
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Hi Eric,

Did you load the same scene file in all of them? If not, this is the best feature ever of this camera to be able to setup one camera, save the scene file on the SD card and load it into the other camera.
After loading a scene file, make sure to set the white balance correct after loading the scene file.
If you use the standard lens, its best to avoid the Iris range below F2,8. Otherwise you get more CA visible of the lens, this tends to give more reds too.
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Old November 3rd, 2006, 02:57 AM   #3
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Hi Eric- I recently did some tests with a lineup of 3CCD HD cameras and lenses, imagers ranging in size from 1/3-2/3." Optics were extremely high end to somewhat low end. We were in a highly controlled setting using optimal calibration instruments and the DIT with me was knowledgeble of each camera's general and engineering menus.

In an attempt to calibrate all the cameras, we discovered that regardless of the 3CCD camera body OR the quality of optics, that if opening up the lens wide open and pointing at a white wall exposed normally, there was lateral chromatic abberation (white shading) occuring with every camera, every lens. Reddish on the top half of the frame and greenish on the bottom half of the frame (or vise versa, can't recall).

The difference with the HD100 in compensating and removing the color abberation was that it did not contain a service menu which would allow the DIT to "dial out" the red and green. The high end cameras were alarming to see this happen with but using a vectorscope, DIT spent no more then 2 minutes eliminating the color abberations and thus we were able then to do a correct white and black balance. I contacted JVC and they said that the HD100 did not have a service menu built into that camera but that the HD250, given it's higher price point etc MIGHT have a menu setting to deal with "white shading" (please don't quote me on that claim as it I have do not know if such a menu will/will not exist on the 200/250).

After fiddelling with every dial on the HD100, we we unable to calibrate it correctly at it's wide open lens position. We found that stopping down 1 stop from wide open is better, and at F2.8 on the HD100 stock lens was the only way to completely remove the lateral chromatic abberation. From that point on, I simply make it common practice to never shoot wider then 2 stops down from the widest point of whatever lens is on the camera. I have not had a calibration issue since that point, so IMOP a perfectly reasonable workaround for a camera at that price point. Hope this helps.

Taylor Wigton
DP, Los Angeles
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Old November 3rd, 2006, 03:06 PM   #4
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Thank you both for your comments, they make sense. The scene file setup does indeed sound like an effecient way to start. Though we didn't have the flash/ram card handy, for this situation, it sounds like a must.

The Director wanted little light so we were working with the arpeture pretty much wide open. And I did see the red/green lateral aberration. It sounds like, if I can close irises to 2.8 or more, and keep them that way, I'll be OK without the colors changing. My iris changes were all from wide to 2.8, so unknowingly I was asking for it. (Although in setting up a lot of cameras, a lot of Sony D-30's for example, I never had this problem before, even wide open.)

And yes, I guess 'painting the blacks is out of the picture without a higher end camera with a good CCU...oh well. Thanks again.
Eric
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Old November 3rd, 2006, 10:21 PM   #5
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I'd also say, welcome to DSP. in post, I had a couple of shots from a shoot with small iris changes. nothing crazy, maybe a 1/2 stop to 1 stop. in the past, with other cameras, I'd simply keyframe a color correction - a little more or less brightness, sometimes gamma, ped and the the change would go away. With the JVC, I'v found I've also had to adjust color too. The only thing I can see doing this is the DSP circuts hard at work trying to optimize the image.as they do so, they are changing the overall color balance in subtle ways that become not so suble once you apply some CC to compensate for an exsposure change. I think this is part of what you were fighting. I've done plently of multi cam with CCU's too. I've got a three camera shoot next week. I plan to setup one camera, put it on a setup card, then jump that setting around to each camera. I also plan to NOT white balance if I don't have to, but stay in preset. its much safer and more consistant for getting the same color.

steve oakley
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Old November 4th, 2006, 12:06 AM   #6
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Steve, good idea. Even if the presets of the different cameras don't match, the iso tapes could be edited using saved color correction presets in post.

I was playing with my Sony FX-1 and seeing none of these problems, so I'm not sure DSP is the problem...I remember being very pleased with the coloremetry in JVC's DV 500 cameras and recommended them to friends as a cost conscious alternative to the Sony 300. Clearly, I need to spend more time with this camera.
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Old November 4th, 2006, 12:59 AM   #7
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We won't shoot open with the HD100 and the factory 16X lens, 2.8 is as far as I would go, as you found it's not pretty without a fair amount of correction in post. No idea if using the improved glass of the 13X has the same result, but I'm sure some people here could tell as a few members have used it.
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Old November 4th, 2006, 10:34 PM   #8
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Quote:
Originally Posted by Taylor Wigton
I contacted JVC and they said that the HD100 did not have a service menu built into that camera but that the HD250, given it's higher price point etc MIGHT have a menu setting to deal with "white shading" (please don't quote me on that claim as it I have do not know if such a menu will/will not exist on the 200/250).
White Shading IS a new feature of the GY-HD250 and GY-HD200U
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Old November 5th, 2006, 04:09 PM   #9
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Carl, can the new cameras apint/adj. the R&B levels in the blacks indepently of the whites?
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Old November 5th, 2006, 09:44 PM   #10
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Quote:
Originally Posted by Eric Lagerlof
Carl, can the new cameras apint/adj. the R&B levels in the blacks indepently of the whites?
Hi Eric,

I looked at the user menus in the manual, and did not find one for independent black level adjustment, just the overall black level. I'm pretty sure that this would be a service level adjustment.

Regards, Carl
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Old November 5th, 2006, 10:29 PM   #11
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Carl, can you please tell me if I can count on the HD200 to be shipping in December? Thank you.
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Old November 5th, 2006, 11:06 PM   #12
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Quote:
Originally Posted by Jaadgy Akanni
Carl, can you please tell me if I can count on the HD200 to be shipping in December? Thank you.

Hi Jaadgy,

As of today, no I can't. We will have a more definitive shipping date towards the end of this month.

If you must have a camera with the new features of the GY-HD200 by the first of December, then you should consider buying or renting a GY-HD250U. These are in stock now at authorized dealers.

Regards,
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