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Message: <blockquote data-quote="John Dracon" data-source="post: 2442539" data-attributes="member: 14799">Steve & Frank -  I decided to measure the lens in the FPO eyepiece that is no longer functional.  It of course is of the Erfle design with one doublet and three other lens air spaced by metal cups.  Interestingly, the diameters vary thus: 25 mm; 29.5 mm; 30  mm (the doublet); and 28 mm.  The Japanese were capable of matching anything the German could produce after WW2, as long as they were porros.  Obviously, the European makers couldn't compete in the porro market and concentrated on the roof designs, with the Japanese catching up slowly in the roof market.  Fuji and Nikon still dominate in their porros.As I have said before, superior coatings have improved many models, but the inherent advantages of the older porros such as the Bushnell Rangemaster will subbornly remain  as real classics.John</blockquote>