Allow me to pose one question for discussion. What determines "depth" of field for terrestrial binocular usage?
My presumption is that "depth of field" or "depth of focus" simply varies inversely with the relative magnification of the object, and has almost nothing to do with the nominal power of the binocular, or its aperture.
I don't think that it really varies with the make of the binocular, as long as we're talking about the same magnification. Of course, I'd expect that the "depth" does improve in better light, simply because one's iris closes down to as little as 2 mm.
But, beyond that, shouldn't the "depth" of focus apparent in my 8 x 32 at 8 feet be the same as in my 10 x 43 at ten feet, or my 18 x 50 at eighteen feet, particularly if I'm using them in fairly bright light where my pupil is 2.75 mm or less? That would be the case because the apparent size of the viewed object is the same.
And as a secondary issue, would the nominal f-ratio of the basic lens, the doublet or triplet objective lens, make any difference? I doubt that it should.
Thanking everyone in advance for their interest, and contribution.
Alan Birnbaum
Fresno, CA
My presumption is that "depth of field" or "depth of focus" simply varies inversely with the relative magnification of the object, and has almost nothing to do with the nominal power of the binocular, or its aperture.
I don't think that it really varies with the make of the binocular, as long as we're talking about the same magnification. Of course, I'd expect that the "depth" does improve in better light, simply because one's iris closes down to as little as 2 mm.
But, beyond that, shouldn't the "depth" of focus apparent in my 8 x 32 at 8 feet be the same as in my 10 x 43 at ten feet, or my 18 x 50 at eighteen feet, particularly if I'm using them in fairly bright light where my pupil is 2.75 mm or less? That would be the case because the apparent size of the viewed object is the same.
And as a secondary issue, would the nominal f-ratio of the basic lens, the doublet or triplet objective lens, make any difference? I doubt that it should.
Thanking everyone in advance for their interest, and contribution.
Alan Birnbaum
Fresno, CA
