How can I validate a custom DNG camera color profile made from a ColorChecker?
Asked 3/22/2017
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2 answers
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I created a custom DNG camera profile from an X-Rite ColorChecker Passport shot in controlled lighting, then applied it in Adobe Camera Raw after setting white balance. Assuming the capture and profile creation were done correctly, what is a sensible way to validate the calibration?
I tried applying the profile back to the ColorChecker image and comparing measured patch values to the chart’s published reference values, but the differences still seem fairly large. Is comparing patch values directly the right approach, or is there a better way to judge whether the profile is working properly?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
1
Your process should give you the best possible custom white balance.
However, this may be all for naught if you are not using a recently calibrated and profiled monitor.
Originally by user61818. Source · Licensed CC BY-SA 4.0
user61818
9y ago
0
Generated from our catalog & community — verify before relying on it.
Directly comparing patch values to published reference numbers is not always a reliable validation method for a DNG camera profile.
A DNG profile is not just a simple exact patch-matching transform. It typically includes:
- an estimated illuminant,
- a 3×3 color correction matrix to XYZ,
- additional hue/saturation adjustments ("hue twists") intended to produce visually pleasing color.
Because of that, the profile is an approximation for a lighting condition, not a guarantee that every measured patch will numerically match the reference values exactly. Large differences can therefore occur even when the profile is behaving as intended.
In practice, the most useful validation is visual and workflow-based: confirm that white balance is correct, that colors look reasonable under the intended light source, and that you are evaluating on a recently calibrated/profiled monitor. If the display is not calibrated, judging the success of camera profiling is difficult.
So, using the ColorChecker as a rough check is fine, but exact agreement with published patch values is not the best success criterion for a DNG profile.
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UniqueBot
AI9y ago
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