Why does an X-Rite ColorChecker Passport profile made in sunlight produce wildly wrong colors?
Asked 11/2/2016
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2 answers
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I’m creating a camera calibration profile for a Canon 7D with the X-Rite ColorChecker Passport software. Profiles made from shadow and indoor-light images work normally, but a profile made from a ColorChecker photographed in direct sunlight gives severely incorrect results when applied in Lightroom. I repeated the test on different days and the software appears to detect the chart correctly.
The bad profile causes major color errors, especially red and blue patches, and the image also becomes darker overall. What could cause this, and what should I check when making a sunlight profile?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
1
It appears something is "flipping" your blues and reds. Pixels that should be interpreted as filtered for red are being interpreted as filtered for blue and vice versa.
If one examines the RGB values for each patch in the original and in the "corrected" photo, one can see that the red and blue values are "flipped" in addition to the additional adjustments that one would normally expect. The second image is also significantly dimmer for whatever reason. This is true even in the gray patches at the bottom of the card. The third gray patch from the left goes from (159,163, 160) to (121,125,123). With colors the effect is even easier to see. The red patch in the third column of the third row goes from (204,53,40) to (17,24,85). The blue patch in the first column of the third row is translated from (43,56,134) to (101,68,84).
Many image editing tools have options to translate/reverse colors. Are you sure you haven't inadvertently selected such a setting?
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
9y ago
0
Generated from our catalog & community — verify before relying on it.
The reported symptom points to a channel-mapping problem rather than normal profile variation: red and blue appear to be swapped, and the profile also darkens the image. That is not expected from a correct ColorChecker profile, even in sunlight.
Based on the community analysis, the most likely issue is that somewhere in the DNG/profile pipeline the camera’s red and blue channels are being interpreted incorrectly. You can see it in the patch values: reds turn strongly blue, blues shift abnormally, and even neutral gray patches get darker.
So the problem is probably not the sunlight itself or chart detection, but a bad DNG conversion/profile interpretation step, software bug, or metadata mismatch for that file. Things to check:
- verify the source file and DNG conversion are correct
- try recreating the DNG from the original raw
- update or reinstall the X-Rite software and Lightroom/ACR
- confirm the camera model/profile support is correct
- compare with another raw converter or another sample file from the same camera
In short: direct sunlight should work, so a red/blue channel swap or corrupted DNG/profile process is the likely culprit.
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UniqueBot
AI9y ago
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