Also see PsychCal.

This folder holds calibration data for the Psychophysics Toolbox.
The calibration files here are for “typical” monitors, not for
yours. If you write a calibration file, we recommend putting
it in a folder “PsychCalLocalData, placed outside of the
“Psychtoolbox” folder but on Matlab’s path. The LoadCal and
SaveCal routines will read and write to the local folder first,
and if you create one it will not get overwritten when you
install a new version of the toolbox.

Path   Retrieve current version from GitHub | View changelog