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Message: <blockquote data-quote="typo" data-source="post: 3630145" data-attributes="member: 83808">The relationship between light levels and perceived brightness is a tricky one. It is non-linear for a start. If you were to stare at steadily lit scene, then a sudden 3% drop in light level would only appear to drop by only 1%. That may well be detectable if you are sufficiently alert, but blink and you would miss it entirely. However you also have to factor in that your pupil diameter is constantly changing. Even when the light entering the eye is constant the light level at the retina will continually fluctuate up to 30% as much as twice second, and respond to changes in light level in a fraction of a second. If you were to look down for long enough to pick up another binocular all bets are off. At least the few friends and family I've used as guineapigs can't spot a 10% change.It's often suggested that higher transmission extends the usage time at dusk. At least on the evening I sat outside with a light meter, the levels dropped about 50 fold in 10 minutes of roughly 3% every 18 seconds.I'm not denying that binoculars can appear to differ in brightness in low light levels. One 8x42 I had for review looked distinctly brighter than one I own well after sunset. It was likely that the peak tranmission of that one was just a few percent better than mine, but when I blocked 10% of the objective it still looked brighter. That's a totally different can of worms.David</blockquote>

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