# Loading a linear LUT to the hardware while using PsychImaging

**URL:** <https://psychtoolbox.discourse.group/t/loading-a-linear-lut-to-the-hardware-while-using-psychimaging/1561>\
**Category:** Uncategorized\
**Created:** [November 1, 2011, 10:28am UTC](https://psychtoolbox.discourse.group/t/loading-a-linear-lut-to-the-hardware-while-using-psychimaging/1561 "2011-11-01T10:28:42Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![craig\_arnold](https://avatars.discourse-cdn.com/v4/letter/c/13edae/32.png) [@craig\_arnold](https://psychtoolbox.discourse.group/u/craig_arnold)\
**Post date:** [November 1, 2011, 10:28am UTC](https://psychtoolbox.discourse.group/t/loading-a-linear-lut-to-the-hardware-while-using-psychimaging/1561/1 "2011-11-01T10:28:42Z")

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Hi all,  
  
When loading a linear LUT to my hardware's graphics card, I still do not always get a true linear relationship between input and display values. This is sometimes causing problems with my Bits++ T-Lock code values being transformed slightly.   
  
I have written a function that calculates and loads an adjusted LUT that will give me a linear relationship. However, when I try to use this in conjunction with the PsychImaging configuration functions ('PrepareConfiguration', 'FloatingPoint32Bit' and 'EnableBits++Bits++Output'), I get the error message:  
  
Error in function LoadNormalizedGammaTable: Usage error  
This window has already a new gamma table assigned for upload on next Flip!  
  
Does PsychImaging load a linear LUT to the graphics card 'for me' and if so, is there any way I can overwrite this with my own, slightly adjusted LUT?  
  
I am using Windows XP, Matlab 2011b, Psychtoolbox version 3.0.9 and an NVIDIA Quadro FX 3450/4000 SDI graphics card.  
  
Thank you,  
  
Craig Arnold