The term "diopter" actually is a measure of lens curvature. It has come to mean, generally, a lens inserted into the viewing system to correct for vision anomalies. Chances are (~75% or so) it replaces the "standard" eyepiece lens - the one nearest the eye of the observer. In the Hasselblad prism, the "standard" eyepiece lens is removed - right hand thread - and the replacement screwed in.Originally Posted by 1manilaboy
Depending, though - it may be an auxiliary lens that fits over the existing eyepiece lens.
Careful, too - some of the so-called "Portrait" or "Close-Up" lenses are labeled in "diopters".
What are the physical dimensions of this puppy?