In looking into higher-power binocular issues, I've tapped knowledge and trends in the telescope realm, to see what might apply to the issue of binocular resolutions seeming to not increase with power as you might expect. It's been mentioned that most binoculars are around f/3 to f/4, a pretty 'fast' ratio (necessitated by the drive to keep length down and the drive for field width), and that this can cause difficulties with resolution. For most binocular powers and aperatures this doesn't matter, since much testing work has shown many binoculars exceeded the limits of the
human eye some time ago. Anyway, on telescopes, f-ratios, and resolution (most easily tracked by recommended 'best power' and 'maximum usable power'. It seems to boil down
to a few trends:
---For f/10 to f/12 scopes, a max usable power of 2 times the aperature in mm and a best-power of 1 times the aperature in mm is cited all over. Actually, it's cited in inches, but it equates to that simple mm formula.
---For f/5 or f/6 scopes, you can still get those power numbers, but only if you at least make the objective an apochromat (3 element or 4) AND use better eyepieces.
The price goes up fast unless you back down to about a little over half those power figures. Common kit eyepieces for fast scopes (that aren't junk) give you powers of 1/2 to 1-1/2 x (D,mm).
( Down at f/3 or f/4 it seems the challenge would be far more severe. )
---At f/10 and up, you can get in range of the Dawes Limit. At f/5 or f/6, only with special optical measures. Below that, it's not so clear. Reflectors can deal with very-fast more easily.
You can see attempts to get the optical length up in some binoculars from makers like older Bresser or old and new Zeiss binoculars. Zeiss even has the light cone tunneling through a long glass section sometimes...pretty amazing. It does keep the physical length down, cranks the f/ratio up. Explains those bizarre cross-sectional drawings.
Bottom line for my eagle-soaring-tracking: just buying binocular power won't work for details. I need to "go long", and even then a decent field width may take a decent load of cash. 50x at 80mm / f6 is possible for not too much, but price kind of explodes for 100x at f6. It wouldn't cost much to see if I can keep up at one mile with f/10. The question: how inconvenient?
It seems that if you're pouring money into special materials in binoculars at 10x or 20x, you're either paying for what you can't see (10x), of you're Sisyphus pushing a boulder up a cliff (20x). Near as I can tell...
human eye some time ago. Anyway, on telescopes, f-ratios, and resolution (most easily tracked by recommended 'best power' and 'maximum usable power'. It seems to boil down
to a few trends:
---For f/10 to f/12 scopes, a max usable power of 2 times the aperature in mm and a best-power of 1 times the aperature in mm is cited all over. Actually, it's cited in inches, but it equates to that simple mm formula.
---For f/5 or f/6 scopes, you can still get those power numbers, but only if you at least make the objective an apochromat (3 element or 4) AND use better eyepieces.
The price goes up fast unless you back down to about a little over half those power figures. Common kit eyepieces for fast scopes (that aren't junk) give you powers of 1/2 to 1-1/2 x (D,mm).
( Down at f/3 or f/4 it seems the challenge would be far more severe. )
---At f/10 and up, you can get in range of the Dawes Limit. At f/5 or f/6, only with special optical measures. Below that, it's not so clear. Reflectors can deal with very-fast more easily.
You can see attempts to get the optical length up in some binoculars from makers like older Bresser or old and new Zeiss binoculars. Zeiss even has the light cone tunneling through a long glass section sometimes...pretty amazing. It does keep the physical length down, cranks the f/ratio up. Explains those bizarre cross-sectional drawings.
Bottom line for my eagle-soaring-tracking: just buying binocular power won't work for details. I need to "go long", and even then a decent field width may take a decent load of cash. 50x at 80mm / f6 is possible for not too much, but price kind of explodes for 100x at f6. It wouldn't cost much to see if I can keep up at one mile with f/10. The question: how inconvenient?
It seems that if you're pouring money into special materials in binoculars at 10x or 20x, you're either paying for what you can't see (10x), of you're Sisyphus pushing a boulder up a cliff (20x). Near as I can tell...
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