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Message: <blockquote data-quote="Surveyor" data-source="post: 3575156" data-attributes="member: 50720">Hi Bill, I thought I would take a whack at this while David gets his thoughts together since I used to do more of it in the past than anyone else on the forum.The key to taking the eyes out of the equation is magnification. My visual acuity is pretty poor, about 90”, or about twice as bad as Kimmo and Henry. For instance if I expect a 7x bino to have about a 4” lp/mm I would need to use an auxiliary scope (booster) with at least 3.5x magnification to get to 24.5x total. This would allow, with my 90” acuity, to see about 3.7” of limiting resolution. I would choose a “booster” of higher magnification, ISO allows up to 45x, see attached excerpt from the ISO 14490-7 resolution specification.Also note the picture of a test I did on a Zen Ray 7x36ED2 posted on the forum several years back. I think I reported at the time a resolution of 4”. Best I can remember now I was able to see group 7 element 1 very well but could not hardly see the vertical bars of element 2. I tried to take a picture of the result but have never been able to get a camera to focus well enough to get to the same point as I do with my eyes.This is used to insure the bino meets the technical requirements and for comparing hardware to hardware. Optics metrics need to meet a certain level even if the average human may not be able to make full use of them. A bad resolution test usually indicates other aberrations in the system. The same reasoning for having standards for collimation, etc.I think ISO 14133 sets out the limit of resolution. This protects consumers with no optics knowledge from buying a pair of Coke bottles joined together that would not make out a car at 50 meters. David (typo) has informed me there is a newer ISO standard out, but I do not have a copy of it.An additional observation, with my acuity of about 90" a 10x bino would have to have a limiting resolution less than 9" to keep from limiting me. A person like Henry Link with an acuity of about 50" would need a limiting resolution of less than 5", very hard to do with objective in the 20-25 mm range.</blockquote>

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