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Klein K80 Negative XYZ Values

 
Author nicholashower
ZRO
Male
#1 | Posted: 24 Sep 2025 06:42 
I am trying to troubleshoot an issue where my Klein K80 measures wildly inaccurate red colours when probe matching is enabled. I am measuring an LG C9 TV.

I am still a learner when it comes to calibration and the maths behind it, but I suspect that the negative Z value of the raw K80 measurement is causing the issue.

Attached are screenshots of the LG C9 native red primary from the K80 (with the blank 0 profile selected) and a CR-250 spectro. Ignore the different code values for red; they were from different patch runs.

I didn't catch the issue at first until I turned on probe matching. The red primary becomes wildly incorrect when matching is enabled.

These negative Z values occur in both Colourspace and Chromasurf. Also, they occur across various profiles (including the blank profile with the identity matrix) in both software programs.

Is this perhaps an issue with my measurement methodology?

Here are the settings I used for both the CR250 and the K80:
-Contact measurement distance
-Stabilization of 3 seconds
-Extra Delay of .5 seconds
-Resolve Patch generator
-25FPS output from Resolve

Or maybe this is a hardware issue with the K80?

Any help would be appreciated.

CR250 Red Primary LG C9
CR250 Red Primary LG C9
K80 Red Primary LG C9
K80 Red Primary LG C9
Klein K80

Author Steve

INF
Male
#2 | Posted: 24 Sep 2025 08:24 
nicholashower
You will need to post the profiles, or at least the CIE graphs of the K80 native, the CR-250, and the K80 matched.
We need to see that actual variation.
(You can also post the Probe Match files.)
But any -Z value means the probe is reading inaccurately, as -Z is not possible in the real world.
Possibly the filters have aged?

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Steve

INF
Male
#3 | Posted: 24 Sep 2025 20:26 
There is also a trick you can use when you are working with wide gamut displays, as explained in the Probe Matching page.
Deliberately put the display into a smaller gamut colour space for the probe matching.
Doesn't have to be a 'real' colour space such as Rec709, just a colour space that is smaller than the display's native wide gamut capabilities.
That will ensure the colourimeter is within its CIE capabilities.
Then put the monitor back into its native colour space before doing the calibration.

Steve
Steve Shaw
Mob Boss at Light Illusion

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 Klein K80 Negative XYZ Values

 

 
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