Here's a quick reminder of the increase in ligh gathering for standard binoculars, the numbers can be added up.
From 20 to 25mm : +56%
From 25 to 32mm : +64%
From 32 to 42mm : +72%
From 42 to 50mm : +42%
From 50 to 56mm : +25%
As a quick note, it is interesting to note that even though the difference between a 50 and a 56mm is "only" 25%, if one takes into consideration that top 56mm use abbe koenig prisms which add another 3 or 4%, we get near 30%, this is the sort of advantage that a Swaro 10x56 HD will have over a 10x50 Swarovision...
Speaking of brightness and binoculars ...
I think that Docter 10x50 Nobilem is a little underrated.
I had the opportunity recently to compare it with Zeiss Conquest 10x56 HD - Abbe Koenig prisms. Also available was the new Leica HD plus 10x50.
Docter not so sharp at the edges of the image as opposed to other competitors - although it has a slightly larger field of view - while the other parameters did not leave them a chance.
Brightness, sharpness in the center, the 3D effect. - Sharpness in the center of the Leica was comparable to Docter.
Outside the building in bright light, the difference in brightness between the binoculars was small.
In a dark room under artificial light, Docter showed what he can do. He was clearly brighter than the Leica and Zeiss.
Comparing all three of binoculars on a busy street in Warsaw, the image of the Leica and Zeiss seemed quite flat in comparison with Docter, although in this fight Leica fared worst.
Taking on the street to hand Docter I thought - this is it!
Docter is also well balanced and shape of binoculars allows comfortable and stable hold in their hands.
It is of course a lot cheaper than the other players, but even if it was expensive, it was worth that money.
At the end of a small note on the guarantee.
Leica 10 years
Zeiss 10 years
Docter 30 years