For a given system, with field type defined as “Real Image height”, the relative illumination at say Y=2mm is say 0.95
For the same system, with field type defined as “Paraxial Image Height”, the relative illumination at still Y=2mm is now 0.92.
Since the Y coordinates of the relative illumination curve are given in mm in the image plane, I would expect the relative illumanition value at a given height is independant of the field type selected.
What am I missing ?