I have a set of close-up diopters for an old Speed Graphic 2-1/4 x 3-1/4
camera. They work okay is you are concerned with an absolutely sharp
They work okay if you don't expect an absolutely sharp image across the
entire frame. A good trick is to make sure that the sharpest part of the
image is closest to the center; people rarely notice any unsharpness away
from the center of a picture. If you look at most portraits of people,
for example, the photographer makes sure that the eyes are the sharpest
part of the picture. People automatically fix on the eyes, and don't notice
or are willing to forgive any unsharpness elsewhere. That's just the way
the eye-brain combo works, I guess.
J. Del Col