I am competent focussing all my lenses at normal distances (>10'), but when I get down in the macro range (<10'), I have a very hard time. To my eye there is a large range around the true focus point that all looks kind of the same.
Is there a workable method to focus via measurement? Say I'm using a G-Claron 240mm, can I measure the distance from my target focus point to the lens, and calculate the correct distance from lens to ground glass? Actually, even if this was only an approximation, it might help me as a starting point. Where on the lens do I measure to?
I have normal 54-year-old eyes, meaning I wear bifocals, but normally I take them off under the dark cloth, just using a loupe.
All advice and pontifications welcome.