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1stScope
member
Reged: 04/22/07
Posts: 44
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Re: Brightness in Exit Pupil
06/17/07 02:57 PM
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I imagine the post below has been previously discussed. In any case after all of these years roof prism binoculars are starting to get close to what good porro prism models have enjoyed all along. This is in spite of what birders and others have prefered, and what I found before buying some FMT-SX binoculars a few years back.
http://www.birdforum.net/showthread.php?t=63770
A friend recently looked at some of the data developed to evaluate binoculars for US Gov't use. Allot of the data refers to immersibility, shock resistance etc. But of particular interest to me was the "light transmission efficiency" rating as a % of total wideband light projected through an aperture 2.5mm x 2.5mm. The ratings for the best binoculars were the Fujinon FMTR-SX and Nikon Prostar (I didn't have a Nikon model # so I don't know if this is the current ED version or previous model) at 97.4% and 97.5%. Then came many, many other binocular models like the Fujinon M-22 (96.2%). I guess the Sandia, Lawrence Livermore, Los Alamos, JPL mandate was to test just about every binocular they could find. But the highest rated roof prism model was the Swarovski SL 10x50 at 93.3%, with the Zeiss FL 10x56 T* right behind at 93.2%.
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