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Message: <blockquote data-quote="henry link" data-source="post: 1375682" data-attributes="member: 6806">Always hard to tease out cause and effect from an optical black box like a binocular. It's easy to assume that some difference we happen to know about must be the cause of an effect we happen to notice. Besides prisms, I can think of at least one other "significantly different optical element" that distinguishes most Porros from roofs. There is a simple cemented doublet objective in the SE and most other Porros vs a 3-5 element objective with wide air spaces and one moving group in most current roofs. The extra complexity in the roof objectives has nothing to do with the prisms. It's just for internal focusing.The only roofs I have around are 8x42 and 8x56 Zeiss FLs with AK prisms. The contrast, light transmission, and sharpness (in the field center) of those compares favorably to the best Porros. If anything they look cleaner and more transparent, but I wouldn't be surprised to find that mid and low priced roofs are not that good. I suspect that in many of those phase correction is not complete, roof edges are not that well made and mirror coatings are not the best.</blockquote>