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  1. H

    Historical Review of Swift 804 Audubon Binoculars

    Renze, My recollection is that RLE (Relative Light Efficiency) was a marketing concept from the early days of AR coatings. The number was derived by taking the old concept of Light Efficiency (the exit pupil squared) and then increasing it by about 50% to represent the increase in light...
  2. H

    Historical Review of Swift 804 Audubon Binoculars

    There is a thread about Chandler Robbins' bins here: http://www.birdforum.net/showthread.php?t=144506
  3. H

    Historical Review of Swift 804 Audubon Binoculars

    Ed, I'm going to have to play the skeptic in this. I'm sure the 804ED is an excellent binocular, but I'm as confident as I can be without seeing it that it still suffers from some of the inherent optical compromises found in other binoculars. An f/4 doublet objective, even with the best ED...
  4. H

    Historical Review of Swift 804 Audubon Binoculars

    Ed, Yes, I have an 8x42 FL. No, it doesn't use Fluorite. It uses one of the fluoro-crown glass types. Zeiss says something like "glass containing Fluoride ions". I can see from tests with the magnification boosted to 64x that longitudinal CA in the FL is about 1/4 the level I see in typical...
  5. H

    Historical Review of Swift 804 Audubon Binoculars

    I'll add my thanks to trashbird for the link to Mr. Ceragioli's work. Chapter 4 is by far the best information I've seen on APO objectives. Notice that all the objective designs under discussion have much higher focal ratios than binocular objectives. The lowest focal ratio even discussed was...
  6. H

    Historical Review of Swift 804 Audubon Binoculars

    You can determine from the outside whether your objectives are air spaced by examining the reflection pattern that returns from the objective surfaces. It requires some careful examination and it's good to know what you're looking for. I've found it's easiest to place a single small light...
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