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Message: <blockquote data-quote="typo" data-source="post: 3430311" data-attributes="member: 83808">Ed,I think the interpretation might be rather more complex than that.The way I read figures 5 and 6 in Holger's paper is that the detection benefit would only occur below 10cd/m2 for a 8x32 vs. 10x40 comparison. That's about the light level when most birders I know are heading home. It shows that for most birding light levels, including a while after sunset, there generally would be no contrast enhancement and the only detail benefit would be the magnification advantage of a 10x over an 8x. Below that level, when the song birds are generally roosting, is when the increased contrast/ detection benefit can be seen, and below that still, the kind of detail increase described by the twilight factor. Of course the luminace, or brightness the eye sees is still identical for an 8x42 and 10x40. That would be in line with my own experience at least.Not an easy message to convey, but the answer is for general birding there is no special benefit from higher magnification, but if you are going owling get a 10x56.DavidResponding to your added comment. These studies look at thresholds for angular size and contrast and generally point to a disproportional enhance performance for higher magnification at lower light levels. But you are right. Birding includes other parameters not considered. Never the less they paint a picture where there is a window of light levels where 'normal' rules apply and lower levels were higher magnifications appear to offer a disproportional advantage. I think it's clear tht colour discrimination will need something like ambient light colour temperature as an additional factor and detection, a different angular size range, to give a couple of examples. I haven't attempted to pin it down but in broad terms, I think 'normal' rules generally apply down to a bit past sunset.  The difference between an 8x32 and 10x56 is a lot, in terms of usable light level but the amount of extra birding time is usually surprisingly modest.</blockquote>

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