Controlling the luminance of the display precisely is important for
many experiments. The Vision Egg allows you to calibrate your display
system and overcome the inherent non-linearity present in most
displays. The result is a system where colors are specified as a
floating point number from 0.0 to 1.0 which produces a linearly
proportionaly luminance on the display. This is acheived by setting
the gamma lookup tables present in the video card.
Here is the result of some measurements I performed on my own display
using a calibrated photometric luminance detector (OptiCal by CRS
Ltd.) and ephys_gui, an application that comes with the Vision
Egg.
This test does not test the calibration near low contrasts near the
threshold for human vision. Video cards with high precision (10 bits
per color or more) gamma lookup tables are well suited for low
contrast experiments. Even better are video cards with high precision
framebuffers, although OpenGL support for this is currently lacking in
all consumer cards that I know about (ATI Radeon 9700 series and
Matrox Parhelia).
I do not have the capabilities to perform color calibration
-- this test was performed by locking the red, green, and blue values
to each other.
