# Gamma calibration problem

**URL:** <https://psychtoolbox.discourse.group/t/gamma-calibration-problem/152>\
**Category:** Uncategorized\
**Created:** [March 2, 2017, 12:55pm UTC](https://psychtoolbox.discourse.group/t/gamma-calibration-problem/152 "2017-03-02T12:55:29Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![jan.kurzawski](https://avatars.discourse-cdn.com/v4/letter/j/90db22/32.png) [@jan.kurzawski](https://psychtoolbox.discourse.group/u/jan.kurzawski)\
**Post date:** [March 2, 2017, 12:55pm UTC](https://psychtoolbox.discourse.group/t/gamma-calibration-problem/152/1 "2017-03-02T12:55:29Z")

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Dear All,

I am experiencing a problem with gamma calibration. Whenever I open a new window&nbsp;and apply&nbsp;

Screen('LoadNormalizedGammaTable', c.display.windowPtr, newLUT)

The screen adjusts the values accordingly to the LUT, however after 2 seconds without any flip or keyboard input it goes back to original values.

When I apply the NormalizedGammTtable again it switches to correct values but again after 2 seconds goes back to original.

I have seen a similar problem on the forum but without any solution.

I am running PTB 3.0.13 on OSX sierra on Macbook pro 2015 with AMD R9370x

Best regards,

Jan