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Message: <blockquote data-quote="typo" data-source="post: 3190206" data-attributes="member: 83808">Ads,I think I should first explain something about light levels. Candela per metre squared isn't going to mean much to many but it's a measure of the light level emitted or reflected from an object in this case towards the eye. It's what makes our pupils expand and contract and consequently changes our acuity. Moonlight would be around 0.1cd/m2, under my 200w room light it's about 80cd/m2 and if I take a reading off a white sheet of paper in direct sunlight it can be up in the 10s of thousands.I checked the luminance of my fridge with the kitchen lights on and got 15cd/m2. Your lights might be brighter of course, but that figure isn't too far from the level where the 4.2mm exit pupil of a 10x42 will begin to be limiting. That's what I would call a low light test. In the US when you go for an eye test they should use 300cd/m2 or 60 fold higher light levels. This is the level where the acuity is best for the average individual, and where you would stand best chance of spotting differences in effective resolution. At higher levels, or more particularly lower levels, your eyesight will be worse. Your eyes will be different to mine but at 15 cd/m2 my eyesight is about 70% worse and I wouldn't stand any chance of spotting effective resolution differences between binoculars. That doesn't mean I wouldn't see contrast differences, what some might term sharpness differences.We know camera lens makers tune the resolution performance to give different levels of detail and contrast. I'm just speculating that some binoculars might be tuned in the same way. It appeared that the EDII may have been tuned for maximum detail at the highest acuity. This would work best in bright conditions. A number of people including myself thought the Zeiss HT 8x54 lacked effective resolution, but this was done in bright conditions. We know Zeiss claimed it was optimised for twilight use and may have been tuned to give the best contrast at a lower level of detail.If you are seeing a perceived difference in contrast/sharpness at comparatively low light levels with your EDI and your FL it sounds unlikely that you would be able to see any effective resolution differences, but you might see any intentional or accidental differences in tuning of contrast/resolution which might make the FL appear sharper. If you get a chance try pinning up the pages in good daylight and see which is better. David</blockquote>

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