# Monitor calibration file with LMS2RGB

**URL:** <https://discourse.psychopy.org/t/monitor-calibration-file-with-lms2rgb/45296>\
**Category:** Coding\
**Created:** [August 1, 2025, 2:57pm UTC](https://discourse.psychopy.org/t/monitor-calibration-file-with-lms2rgb/45296 "2025-08-01T14:57:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Alex\_Wade](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/alex_wade/32/4350_2.png) [@Alex\_Wade](https://discourse.psychopy.org/u/Alex_Wade)\
**Post date:** [August 1, 2025, 2:57pm UTC](https://discourse.psychopy.org/t/monitor-calibration-file-with-lms2rgb/45296/1 "2025-08-01T14:57:54Z")

</div>

Hi! I’m trying to generate spectrally calibrated monitor files. I have measured spectra from my monitor and can generate LMS2RGB matrices that look almost identical to the default internal matrix used by psychopy

```auto
    # L M S
    [4.97068857, -4.14354132, 0.17285275], # R
    [-0.90913894, 2.15671326, -0.24757432], # G
    [-0.03976551, -0.14253782, 1.18230333]]) # B

```

. When I enter this into the monitor center (or, build a monitor file with the matrix embedded) , Psychopy seems to ignore it and falls back on its default. It \>does\< parse the monitor file and it \>does\< accept my gamma parameters. Could some one please share a .json of a valid, spectrally-calibrated monitor file so that I can see what I’m missing?

When I run, no matter what’s in that LMS2RGB matrix, I get a string of errors saying:

WARNING This monitor has not been color-calibrated. Using default LMS conversion matrix.

This happens even if the monitor calibration matrix is \>identical\< to the internal default.

Thanks

Alex