Anyone know how these work?
Looking at the spec for leica ultravids and swarovski slc models I started to assume that the higher the twilight rating the brighter the image,however
the 10x42 models from both manufacturers all have higher twilight ratings than the 7x42?
Swarovski slc,
8x30-twilight factor of 16
7x42.........................17
10x42.......................21
Leica ultravid
8x32-twilight factor of 16
7x42.........................17.1
10x42.......................20.5
I would have thought the 7x42 models would be brighter,hence have higher
twilight factors..but they don't?
Matt
Matt;
I am no expert but my thoughts. The twilight factor is just the square root or the power times aperture and on considers binos and does not account for eyes. If your eyes can open to 5 or more mm, the 7x42 should be brighter by a factor of around 2. If you are like me and can only dilate about 4.5 or maybe 5 mm on a good day, it would probably be a toss up depending on subject or many other factors. I am sure someone more knowledgable than I will be along shortly and be able to explain better.
Ron
Ron put it well. Twilight factor is not a real accurate number. The thinking behind it is that magnification and aperture add datail. Increasing either in the formula results in a "better" score. This does not take into account any sort of usefullness and is a very bad way to compare binoculars. Extrapolating the math results in such comical results as a 50x25 binocular doubling the performance of a 7x42! See the flaw?