Why Does a darktable Color-Checker Calibration Improve Average Patch Error but Make My Brand Color Less Accurate?

Confirm that the calibration input is suitable

darktable documents supported color-checker models and specific capture conditions. The chart should be photographed under the relevant lighting, without distracting reflections or strong illumination gradients. The correct chart edition must be selected.

Its manual also explains that color-checker calibration settings depend on the camera input profile, White Balance, and chromatic-adaptation configuration. A profile copied to a different pipeline is not automatically equivalent.

Before comparing optimization strategies, preserve the original chart capture and record the chart model, lighting, camera profile, and relevant module settings.

If the chart was captured under a different illuminant from the product, do not treat the calibration score as direct proof of the product's appearance under the new light.

Read average, maximum, and individual patch errors

darktable's profile report uses delta E 2000 to describe perceptual differences between reference and processed chart patches. It reports average and maximum errors and displays per-patch indications.

The manual documents several optimization choices. Average delta E attempts to reduce the overall average. Maximum delta E emphasizes large outliers. Saturated colors gives greater priority to highly saturated colors, which can be useful for commercial product photography.

These objectives can conflict. A lower average may coexist with a larger error in one important saturated patch. Conversely, protecting a difficult color can increase errors elsewhere.

Do not choose the strategy solely by whichever summary number is smallest. Identify which colors are essential to the photographed product, then examine their corresponding chart evidence and the actual product appearance.

Hypothetical saturated-orange carton

Hypothetical illustration—not a measured chart calibration: a merchant photographs a carton with a saturated orange brand panel under one controlled studio setup.

The proposed comparison uses the same supported chart capture and pipeline settings while changing only the documented optimization strategy. Version A minimizes average delta E. Version B prioritizes saturated colors. Version C minimizes maximum delta E.

The reviewer records average error, maximum error, the relevant orange-like patches, and the carton itself. No numerical errors are supplied because the calibration has not been executed.

If A produces the lowest average but an unacceptable orange-panel mismatch, that does not make the overall average meaningless; it means the chosen objective does not adequately serve this particular product-color decision.

If B improves orange while damaging neutral packaging regions, the merchant must decide whether another capture, lighting setup, or profile is needed rather than automatically accepting B.

Choose a profile for its actual evidence scope

Compare the candidate profiles under the same output and viewing conditions. Use the chart report to understand the tradeoffs and a verified physical product reference to judge the relevant merchandise appearance.

Keep lighting and input-profile assumptions with the saved preset or Style. darktable explicitly notes that difficult illuminants can limit calibration accuracy and that a computed profile is a best-fit solution, not a perfect reconstruction of the entire color spectrum.

If no strategy keeps critical colors within the required review boundary, investigate the light source, chart capture, and camera profiling rather than repeatedly optimizing the same unsuitable data.

Accept the selected profile only for the stated camera and lighting context. A low average chart error does not independently certify every product color or every display.

Record your own observations

The filled rows are illustrative examples. Use the blank row for your own files and observations.

Download the editable CSV worksheet

What the references establish

• darktable User Manual — Color Calibration: Documents supported charts, calibration prerequisites, delta E reporting, and optimization strategies for average, maximum, and saturated-color errors.