. Does anybody know the percentage transmission of a completely optically clean 1985 Swift HR 5 8.5×44 binocular?
Is the percentage transmission of a later model greater?
All the best.
I've owned two 804 HR5 MC from the 1980s and three FMC from the 1990s including the ED version, and the FMC were noticeable brighter, more color neutral, and had better color saturation. The ED version had the smallest sweet spot and the most pincushion.
For stargazing, my MCs were better because they had larger sweet spots and very low astigmatism and coma started >75% out and didn't get bad until the edge. The FMC had more aberrations but were better for birding because of their more advanced coatings. Very, very sharp images.
Ideally, I'd like a FMC 804 with as good edges and lower distortion like the MCs.
Brock
The MC and FMC versions of the 804 HR/5 Audubons differ only in lens coatings. The optics and mechanics are otherwise the same. In fact, the parts are interchangeable. The 804 ED has a somewhat different opto-mechanical design, but was also produced with different multi-coating variations.
Astigmatism, coma and distortion are monochromatic aberrations that do not vary systematically with lens coatings. I very much doubt that the "sweet spot" varies with lens coatings either. However, since there is no optical definition for it, anything goes.
For sky observation I'd strongly recommend considering a late-model 10x50 HR/5 Audubon Kestrel, which were manufactured until about 2002 and were fully multi-coated. They're also a great birding binocular.
Ed
Thank you very much Ed for Post 8.
Most helpful.
P.S.
What is the field of view of the 10x50?
Do HR/5s vignet?
10x50 7.0 degrees maybe.
This is a nice find, virtually mint condition Audubon Gold Band model, case and all straps never used, boxed with all it's original bits and bobs. I have a slightly earlier one of these, just as good really. see <a href="https://www.flickr.com/photos/95019762@N07/10244486083/in/dateposted-