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Message: <blockquote data-quote="henry link" data-source="post: 1280479" data-attributes="member: 6806">I 'm not sure I want to get too far into this, but I can offer some measurements that suggest there can be much better resolution at the focal plane of a good roof prism binocular than 40 lp/mm. The best 42mm binocular I've measured with the USAF chart (Zeiss 8x42 FL at 64x) has resolution of about 3 arc seconds, close to diffraction limited. I can only see about 11-12 arcsec looking directly through this binocular at 8x, so it's resolution is about 4 times better than my eyesight. Math is not my strong suit, but working Ron's method backwards, the resolution of this binocular would appear to represent something close to 400 lp/mm at the objective focal plane, which would be about right for a nearly diffraction limited f/4 objective. Someone check my math, please! The Swarovski objective lens in the test might have been 30mm. The 8x30/7x30 SLC and an 8x20 were the only roof prism binoculars Swarovski made in 1991.</blockquote>