DisplayCAL White Point Wrong? 6500K Measures as 6400K

You set the white point target to 6500K (D65). You run the calibration. The measurement report comes back: 6400K, for both target and result. You try “as measured”, you try manual 6500K, you re-measure. Still 6400K. This exact behavior was reported in GitHub issue #411.

The Reported Case

The reporter was creating a Video 3D LUT for DaVinci Resolve (not an ICC profile) on a BenQ EW3270U connected through an UltraStudio Monitor 3G to a MacBook Pro, using DisplayCAL-py3 3.9.13 with ArgyllCMS 3.3. Key detail: with the older 3.9.12, the same monitor calibrated to about 6500K without trouble, so something in the 3D LUT workflow settings was off, not the panel.

First: Rule Out the Usual Suspects

  • Warm-up. Measure only after the display has been on for 30+ minutes. A cold panel drifts.
  • Ambient light. Changing room light between setting the target and measuring shifts readings.
  • Wrong correction (CCSS). If your colorimeter uses a spectral correction for the wrong panel type, white point readings skew. See our CCSS guide.
  • Observer mismatch. ArgyllCMS 3.4+ renamed the CIE 2012 observers to CIE 2015. Stale observer settings can shift results slightly.

The Fix That Worked (Community-Reported Settings)

Attribution: these settings were reported by community member Adam-Color in issue #411 after hours of trial and error. They are user-reported, not official guidance, but they produced a correct white point where the defaults did not.
  1. In DaVinci Resolve: use video levels.
  2. In DisplayCAL: use full levels all the way through.
  3. Turn drift compensation off.
  4. Set black level to as measured.
  5. Set tone curve to as measured. (The reporter noted tone curve calibration appears broken in this workflow.)
  6. Set black output offset to 100%.
  7. Use absolute gamma.
  8. Set rendering intent to preserve saturation.
  9. Turn apply calibration (vcgt) on.

With these settings, the reporter got a solid calibration result with the proper white point. The maintainer acknowledged the 3D LUT workflow may have a bug in 3.9.x and said it was worth investigating.

If the Numbers Are Close but Not Exact

A white point landing within a few dozen kelvin of target is often measurement variation, not failure. Instruments, panel drift, and observer math all contribute. What matters is the verification report: if it shows the target was hit within tolerance, the calibration did its job. For the visible match between two displays, DisplayCAL’s alternate white point editor lets you nudge the white point until the screens look identical to your eyes, useful when two panels measure the same but look different.

Still Not Working?

  • Update everything. The issue thread suggests upgrading to the latest DisplayCAL, Python, and ArgyllCMS. The reporter’s older 3.9.12 behaved correctly, so a regression is possible.
  • Try the ICC profile workflow as a control test: if a normal display profile hits 6500K but the Resolve 3D LUT path does not, the problem is isolated to the 3D LUT settings.
  • Check our Resolve 3D LUT settings guide for the full recommended configuration.
  • Report it. Add your display model, connection chain, and versions to issue #411.

Related: DisplayCAL troubleshooting hub | Quickstart guide | How to read your verification report

Frequently Asked Questions

Why does my 6500K target measure as 6400K?
In the reported case (GitHub issue #411), the white point read 6400K in the measurement report no matter what target was set, specifically in the Video 3D LUT for Resolve workflow. A community member’s settings (video levels in Resolve, full levels in DisplayCAL, drift compensation off) resolved it for them.
Is a 100K white point error visible?
A 100K deviation around D65 is small and usually not visible in isolation, but it indicates the calibration did not hit its target. Worth fixing because it suggests a settings mismatch rather than a real panel limitation.
Should I use the ‘as measured’ white point?
If your panel cannot physically reach the target, ‘as measured’ avoids fighting the display. But if the panel can reach 6500K and the report still shows 6400K, the problem is in the workflow settings, not the panel.
Does the observer setting affect white point?
Yes. Different standard observers compute slightly different white points from the same measurement. ArgyllCMS 3.4+ renamed the CIE 2012 observers to CIE 2015; mismatched observer settings can shift readings.