Re: Nonlinear camera sensors
Re: Nonlinear camera sensors
- Subject: Re: Nonlinear camera sensors
- From: David Iannarelli <email@hidden>
- Date: Wed, 02 Feb 2005 20:00:33 -0500
I have been evaluating a calibration system for digital cameras and I found a
possible problem:
There is a shift in white balance vs. illumination level. In other words, there is a color shift depending of the grayness of the gray card.
This ought to affect the profiling of cameras. For the details see:
http://www.vinland.com/Contrast.html
Is this problem isolated to my camera or is it generic to all or only some brands of cameras?
Hi Bertho,
I have noticed this with my Fuji S2 Pro and Olympus E-20. The S2 manual says to use a white card when making a custom white balance in camera. I went back to a white card for the S2 because of my test with different gray cards but, I have not tested different white cards to see if the camera gave me similar results to the gray card test.
I shoot in the RAW format only and I now shoot a GretagMacbeth ColorChecker as my primary white balance practice and use a RAW processing software to gray balance the image using the third patch from the left before applying a camera profile. I measured all the gray patches on my chart and found that this patch was the most neutral. I stress most neutral. None of the patches were completely neutral. We are talking a L*a*b* value of 1 or 2 points here though.
I think using the same card to set your white balance and then build your profile with that is more important than which card you use. As long as you get a neutral gray from your white balance and the final print is the colors you wanted the subject to be, what else can you expect? I believe the non proprietary ICC profiling technology has only been in use since the early 90's. There is definitely room for improvement. Gelatin film technology started over 100 years ago. It will take some time for digital to catch up.
David Iannarelli
email@hidden
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