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Exit pupils

337 Views 4 Replies 3 Participants Last post by  vmaxx
Can someone tell me what is a good size exit pupil on say a varible scope set on 12x. Thanks in advance for any responses.
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There's a very comprehensive article on the subject in the latest American Rifleman. If memory serves, they said the largest exit pupil is 7mm, but I think that can change within the same scope depending on magnification, and objective diameter. I'm working on a re-read of the article myself, and would hesitate at this point to state many facts.
thanks phil

I was hoping that some one with knowledge such as yours would come along. You taught me something
Exit Pupil


As phil in alabama has stated, the maximum a human eye's pupil will dilate in total darkness, after dark adaptation [~ 30 min.], is 7mm. That is why Navy "watch binoculars" are 7x50mm...! ! :)

The "Simmons" WTC18 [6.5-20X 50mm AO] is known to be a very "bright" scope, even at 20X; it has an exit pupil of 2.5mm at 20X...! ! ;)

Relative Brightness, useful when comparing one scope to another, is:

RB = [ Objective Lens Dia. (mm) / Power]²

The WTC18 has a RB of 6.25

The 44 Mag has a RB of 4.84

So, the WTC18 is 29% "brighter" than the 44 Mag, just going from a 44mm AO to a 50mm AO...! ! :)

But, if you have a Grand to spend, there is the Swarovski 8x56 with an exit pupil of 7mm, and a RB of 49; it is an extremely bright scope...! ! :eek:

Judge accordingly.....! ! :)
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Thanks bigmike

I am glad someone here could put me in the know about these scopes. Its confusing to me at times.
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