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Message: <blockquote data-quote="chartwell99" data-source="post: 294608" data-attributes="member: 5367"><p>Admittedly this stuff gets a little esoteric, but my understanding is that the Leitz Trinovid bins relied on remarkably complex Uppendahl  prisms. Zeiss then and now used both Schmidt-Pechan prisms and Abbe-Koenig prisms, and everyone else making roof prism glasses (now including Leica) used Schmidt-Pechan prisms. Unlike porros, all of these roof prism designs rely on reflection as well as refraction to invert the image, and, consequently, all require phase coatings to deal with the sharpness problems associated with out of phase light waves resulting from the use of reflective surfaces. Zeiss claims that the Abbe-Koenig prisms (actually a very old Hensoldt design) are the most efficient, although not the most compact. I suspect that cost rather than design inefficiency doomed the Uppendahl approach, but the 7 x 35 Trinovid would have been a wonderful glass updated with phase coating and modern multicoatings.</p></blockquote><p></p>