Adhoc,
As I indicated in #11 I don't really know enough about you, the binoculars, and the conditions when you did the comparison to have much Idea. What was the nature of the detail you were comparing and how dark was it? Do your pupils dilate to 5.6mm?
On the face of it, in terms of resolvable detail (Zeiss) the 10x should have had about a 20% advantage over the 8x (allowing for a bit of hand shake) at the tail end of daylight, improving to around 30% by moonlight. For the contrast threshold, it would again be about 20% at the end of day, increasing to 50-60% by moonlight. Both sets of figures assume that the transmission and other optical properties of the two binoculars are the same. In this case they are probably not, but even an aluminium versus dielectric mirror difference (?) shouldn't reverse that kind of advantage on it's own by moonlight.
You say the comparison was at night. The Zeiss and Leica calculation roughly hold for the 0.3 down to 0.003cd/m2 light range, which approximates to moonlight levels. If your comparison was instead at the tail end of daylight, say around 1-5 cd/m2 where there is still some colour vision, then under the blue ambient light after sunset I guess it's possible that a large difference in short wavelength transmission could make such a difference, but that's wild speculation. It's probably a combination of a number of number of things.
David
Thanks, again, David.
Myself
I reckon: acuity 20/15, pupils dilate to about/at least 5 mm, not at all sure about 5.6 mm.
Instruments
The 8x42 had di-electric coated prisms, the 10x56 did not.
To remind, they were a Leupold McKinley 8x42 and Barr-&-Stroud Savannah-ED 10x56.
Conditions
By "night" I meant several hours after dusk.
May be a little moonlight, not much. I remember the darkness was such that either the moon was not bright or was covered by clouds.
Tested on distant trees lit by the sky, and
nearer trees partly reached by the light of street lamps, which was more "neon" in color, if that is the word, not amber.
Results
Instantly on raising to the eyes the image with that 10x56 definitely looked brighter.
But after those first moments there was definitely more information through that 8x42 than that 10x56,
on outlines of trees,
details of foliage and structure within them,
and more and better rendition of color:
of leaves, branches, fruits.
I remind, in daylight (also) the 8x42 conveyed more detail than the 10x56.
Hope there is at least some useful info. in there!
Adhoc