>Psychtoolbox>PsychCal

[gammaTable1, gammaTable2, displayBaseline, displayRange. displayGamma, maxLevel ] = CalibrateMonitorPhotometer([numMeasures=9][, screenid=max])

A simple calibration script for analog photometers.

Use CalibrateMonSpd() if you want to do more fancy calibration with
different types of photometers or special devices like Bits+ or DataPixx,
assuming you know how to operate CalibrateMonSpd() that is…

numMeasures (default: 9) readings are taken manually, and the readings
are fit with a gamma function and piecewise cubic splines. numMeasures -
1 should be a power of 2, ideally (9, 17, 33, etc.). The corresponding
linearized gamma tables (1 -> gamma, 2 -> splines) are returned, as well
as the display baseline, display range in cd/m^2 and display gamma. Plots
of the two fits are created as well. Requires fit tools.

If the normalized gamma table is not loaded, then the cd/m^2 value of a
screen value can be figured out by the formula: cdm2 =
displayRange*(screenval/maxLevel).^(1/displayGamma) + displayBaseline.

Generally, you will want to load the normalized gamma tables and use them
in Screen(‘LoadNormalizedGammaTable’). For example:

[gammaTable1, gammaTable2] = CalibrateMonitorPhotometer;
%Look at the outputted graphs to see which one gives a better fit
%Then save the corresponding gamma table for later use
gammaTable = gammaTable1;
save MyGammaTable gammaTable

%Then when you’re ready to use the gamma table:
load MyGammaTable
Screen(‘LoadNormalizedGammaTable’, win, gammaTable*[1 1 1]);

History:
Version 1.0: Patrick Mineault (patrick.mineault@gmail.com)
22.10.2010 mk Switch numeric input from use of input() to use of
GetNumber(). Restore gamma table after measurement. Make
more robust.
19.08.2012 mk Some cleanup.
4.09.2012 mk Use Screen(‘ColorRange’) to adapt number/max of intensity
level to given range of framebuffer.