What I am trying to do is to use only two channels for my stimulus. Basically, I would like to have the red always to 0 (in rgb255 notation).
I tried different methods, like using my window in “add” or “avg” mode, but none could solve this problem.
With the add mode, I understood that black values are for subtracting color so I tried:
having a turquoise window ([-1,0,0])
add a grating stimulus
add a rectangle on the whole image with values [-1,0,0] -> The red should be subtracted and green/blue unchanged
Quote from documentation for blendMode add:
“The sum is performed using the signed values of the color representation in PsychoPy, with the mean grey being represented by zero. So a dark patch added to a dark background will get even darker”
Many thanks !