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Loading gamma table

Hi all,
In Psychtoolbox, it is possible to load a specific gamma table that will be used when displaying images or movies, using the Screen(‘LoadNormalizedGammaTable’) function. Is this possible within PsychoPy, or when using moviestim?
Thank you
ilkay

You would usually do this using psychopy.monitors:

http://www.psychopy.org/api/monitors.html#psychopy.monitors.Monitor.setGammaGrid

I also have a similar question.

I understand that psychopy.monitors is where to set specific monitor values, but I’m confused how to translate between Psychtoolbox’s ‘LoadNormalizedGammaTable’ and pschopy.monitors.setGammaGrid.

In Psychtoolbox, you give it a whole set of values (255 values) [0 - 1] (consider this an x-value) and corrected gamma values where each value is a y value s.t. y = A*x^(1/gamma) (where you fit A and gamma from measurements).

In Psychopy.monitors.setGammaGrid, all this wants is min, max, and gamma. I don’t see how this is equivalent. Could someone please explain?

I think you could achieve something similar by setting win.gammaRamp after opening a window. See psychopy.visual.gamma.setGammaRamp for details.

Thank you for your response! I’m sorry but I have an additional question: I’m reading that win.gammaRamp is 3x256 (or 3x1024). Is there a reason it’s not 4x256 (for ‘gray’, ‘r’, ‘g’, ‘b’)?

Thanks!

It is setting the output of the three monitor channels (red, green, blue) for a given input - there is no grey channel as such. This is presumably the same in PsychToolbox’s LoadNormalizedGammaTable.