[Leica] Ground Glass Focusing on M Cameras

[Harry Haige <haige@compuserve.com>]

Hello Ken Iisaka,

Thanks for your comments.  I tried to eliminate operator induced errors;
let me know if the following is not valid.  I put a microfine target at the
focal plane of the camera and illuminated it alternatively with red, green,
and blue transmitted light via Wratten filters.  I observed the target with
two different 30X Leitz magnifiers and the target was "perfectly" sharp
with all three colors once focused with any one of the colors, and without
moving anything.  As best my eyes could tell.  On the other hand, when
observing images at the focal plane produced by camera lenses, the
different colors of the subject are not in focus at the same time. 
Therefore, I attributed the chromatic abberation effect solely, or at least
predominantly, to the camera lens.