10x-21x50?

[olds]

Never noticed binoculars with 3 numbers before.
I guess magnification is adjustable between 10-21 and the aperture is 50?

 

[Scotteq]

Correct - They zoom from 10 to 21 power, and the objective lens is 50mm

 

[fuzzybabybunny]

And as a result the aperture changes as you zoom as well.

50mm / 10 = 5mm exit pupil, which creates a relatively bright image when you look through it.

50mm \ 21 = ~2.5mm, creating an image approximately 4 times darker than the one at 10x zoom.

 

[highland145]

And as a result the aperture changes as you zoom as well.

50mm / 10 = 5mm exit pupil, which creates a relatively bright image when you look through it.

50mm \ 21 = ~2.5mm, creating an image approximately 4 times darker than the one at 10x zoom.

Yeah, found out 1st hand on my new 6X18-40 sweet 22 BSA today. Also found out that the bolt spring should not be pressing on the sear instead.....YMMV.:ninja: