You can find this filter through
-> -> .
Retinex improves visual rendering of an image when lighting
conditions are not good. While our eye can see colors correctly when
light is low, cameras and video cams can't manage this well. The
MSRCR (MultiScale Retinex with Color Restoration) algorithm, which is
at the root of the Retinex filter, is inspired by the eye biological
mecanisms to adapt itself to these conditions. Retinex stands for
Retina + cortex.
Besides digital photography, Retinex algorithm is used to make
the information in astronomical photos visible and detect, in
medicine, poorly visible structures in X-rays or scanners.
“Retinex” filter options
These options call for notions that only mathematicians can
understand. In actual practice, user has to grope about for the best
Here is what the plug-in author writes on his site
characterize color variations and the lightor, we make a
difference between (gaussian) filters responses at different
scales. These parameters allow to specify how to allocate scale
values between min scale (sigma 2.0) and max (sigma equal to the
As the MSR algorithm tends to make image lighter, this slider
allows you to set color saturation.