> > A zone plate focusses like a lens so you should adjust the focus for > objects at different distances. On the other hand, they tend to have > large f numbers (like f/32) so they have large depth of field. They are > also hard to focus because they are so dim.
I congratulate you folks who can focus one of these things through the viewfinder. I pulled out my Crown Graphic, slapped on the reflex viewer, tried focusing on a light source, tried focusing on a subject outside, and I really couldn't tell any difference except at the extremes. Maybe if I use a loupe. Maybe not.
