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Message: <blockquote data-quote="typo" data-source="post: 3189928" data-attributes="member: 83808">John,I think you've just illustrated one of the difficulties. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" />These are some of the terms I would use.To me resolution is a property of the binocular as an instrument, the figure some of us get through boosted resolution testing and the professionals by MTF. Unfortunately that figure is relatively unimportant when you put the binocular to the eye, and the effective objective diameter of the image reaching the retinal is dictated by the pupil of the eye. This I'd call effective resolution and it changes constantly.The resolution of the eye is called acuity and it changes with light level and pupil diameter. With a binocular it should improve by same the factor as the magnification to give you effective acuity. The limit of detail you can actually see might either be dictated by effective resolution or more usually the effective acuity. With the two binoculars I referred to above, in bright conditions for me the Vanguard was effective acuity limited and the Zeiss was effective resolution limited. Normally I would say the Vanguard was sharper, but the dilemma we have is that the Zeiss may have been tweaked to improve contrast in low light. Is it right to call the Zeiss sharper in low light? I think not but I'm open to suggestions.If we had access to the MTF analysis and it was more widely understood it might be easier to communicate these things. It's been suggested that MTF 50 might be a good indicator of perceived sharpness and MTF5 the resolution, but I can't envisage the manufacturers releasing that data, particularly for a range of objective diameters.David</blockquote>

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