Thanks for looking, Joel. I see what you mean. It seems a petal or two should
be close enough to the focal plane to be rendered more sharply. I would
postulate it is in part related to a more abrupt loss of sharpness away from
the center from the CU diopter. The lens itself has minimal field curvature.
Perhaps a small stack may still have helped some for some of the petals on the
left. I had the focus step on the focus bracket on “3” (a mistake) and back to
“1” for macro would be a menu dive— we were hiking.
One can get a clue if the optics of the lens and CU diopter might work well
together by investigating the FL of the lens for which it was designed, but it
must be empirically determined if the marriage is suitable.
Ask MTM (Moose the matchmaker), Mike
Themed Olympus Photo Exhibition: http://www.tope.nl/