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Message: <blockquote data-quote="typo" data-source="post: 3509923" data-attributes="member: 83808">I use something referred to as boosted resolution testing and a copy of a USAF 1951 resolution chart like most amateur testers. Industry professionals use modulation transfer function (MTF) analysis which will produse supplimentary information. Conventionally it's the instrument resolution that is measured and that form the basis for the ISO standards for binoculars. However, optimal visual acuity occurs at fairly high light levels when the pupil of the eye typically 2.5mm. The light from the periphery of the objective is then blocked by the iris of the eye. The image at the retina is then formed by the diameter of the objective corresponding to 2.5mm multiplied by the magnification. It is the resolution corresponding to this diameter what I refer to as effective resolution. If the effective resolution magnified is lower than your acuity then the binocular will be eye limited. If not, the binocular will be limiting. For an 8x binocular I would measure 20mm. A typical result for current mid to high priced binocular would be 6.5 arcseconds. Magnified 8x that is 52 arcseconds. This would exceed the visulal limit of even those with 'perfect' 60 arcsecond eyesight. However this is not always the case. I have had results at around 80 arcseconds for mid priced models which would still be satisfactory for those with average eyesight, but inadequate for those with the best vision. The worst sample I've tested was 120 arcseconds and would still adequate for those with 20/20 vision but look soft to most users.Hope that helps.I'm a scientist not an optical engineer. David</blockquote>

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