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extra aperture: wasted or beneficial?

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#1 Guest_**DONOTDELETE**_*

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Posted 18 April 2004 - 05:56 AM

Suppose my fully dark-adapted pupils dilate to only 5mm. I want to choose either 7x50s or 7x35s...and both have the same field of view.

I always hear that the 7x35s will show just as much, since the extra aperture of the 7x50s is wasted...some if its light will fall uselessly on my irises. But won't the 7x50s have better resolution due to the larger objective size?

#2 lighttrap

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Posted 18 April 2004 - 07:28 AM

Patrick, if you go to the top of this forum, you'll find a "Best Of" post. Click on that and scroll down til you find the post on exit pupils. This topic has been discussed at great length.

As for 7x50s having better resolution than 7x35s: resolution is more a factor of the quality of the optics than the size. But, you are right to the point that all else being equal (and it rarely is), the larger objectives will generally (notice the hedge word, generally), have a larger "sweet spot" where the effects of lens curvature are less pronounced.

Mike Swaim

#3 EdZ

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Posted 18 April 2004 - 08:18 AM

To see a significant difference in what each size lens could provide for resolution, other than simply due to the quality of the binocs, you would need to have magnifications of somewhere between 12x per inch to 30x per inch. Binocular magnifications of 2x to 6x per inch will not show much difference in resolution due to objective diameter. So as Mike said, the biggest difference you will see in resolution will be contributed by the quality of the lens, not the size.

edz

#4 Guest_**DONOTDELETE**_*

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Posted 19 April 2004 - 06:44 AM

Thanks Mike and Ed...this is the info I was looking for.

Interesting info there about ease-of use of large exit pupil binocs. I knew the large exit pupil makes eye positioning much less fussy, but I didn't know that it can accomodate more eyeball swiveling than smaller exit pupils. I like 7x50s even more now that I know why they're so comfortable to look through.

I just wish there were some wide angle 7x50s available today. (The widest angle ones I've found are Nikon Sport & Marine 7x50s...about 7.5 degrees according to the manufacturer...which is only about 52.5 degrees apparent.)

#5 wilash

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Posted 19 April 2004 - 07:59 AM

Thanks Mike and Ed...this is the info I was looking for.

Interesting info there about ease-of use of large exit pupil binocs. I knew the large exit pupil makes eye positioning much less fussy, but I didn't know that it can accomodate more eyeball swiveling than smaller exit pupils. I like 7x50s even more now that I know why they're so comfortable to look through.

I just wish there were some wide angle 7x50s available today. (The widest angle ones I've found are Nikon Sport & Marine 7x50s...about 7.5 degrees according to the manufacturer...which is only about 52.5 degrees apparent.)


Miyauchi have just release a pair of 7x50s with a FOV of 9.5 degrees. About $700 to $800 US dollars. Nearly 3lb (1.3kg). Eyepieces focus individually. 66 degree AFOV. The main objectives are 160mm f/3.2 and the EPs are 22.8mm.


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