Exit pupil........

[Mark204]

I'm looking for an answer as it pertains to the exit pupil on a variable powered scopes. A person I know claims that the exit pupil is only relevant to fixed powered scopes and not on a variable powered scope, which contradicts what I know, (or think I know).

I told him that my Nightforce 5.5x22-56 had an exit pupil at 22x of 2.5mm, (objective divided by power equals exit pupil), which he says is not possible. I have more than one scope which falls in that range at a max power setting, some higher, some lower. I have NEVER claimed to know it all, but I do know that Nightforce, Zeiss, Swarovski and Schmitt & Bender post their exit pupil in the specs sheet. I will concede glass is a factor, but this is solely about exit pupil, nothing more.How do you argue with numbers from the maker of any scope as it pertains to exit pupil, high or low, its a number, you can't say it doesn't exist.

Consider me stupid, but I will take the manufacturers data over a retired gun smith, the same person who bases his position on barrel-break-in , (as useless) from someone who died 20 years ago.

Any insight?

Mark

 

[wkdickinson]

If you GOOGLE "exit pupil" you will find lots of info. But basically the "exit pupil" of any telescope can be calculated by dividing the diameter of the objective lense (in mm) by the power of the scope. So in the case of a variable power rifle scope, the exit pupil will will get larger or smaller inversely to the power the scope is set to.

 

[Pwc]

For my astro telescopes, use 7mm as that is the pupil size for a fully dark adapted eye. Anything larger is wasted, less is dimmer. Now for daylight....smaller size may work because it is brighter; I think would allow some error in eyeplacement; don't know about paralax tho.

Same is for binoculars, 7mm is the practical limit...10mm allows your eye to wander around the eyepiece. More $$ for exit pupil over 7mm is wasted.

 

[rammac]

I'm 61 years old and the worst guys to argue with are old retired folk, they made up their minds 40 or 50 years ago and you'll never get them to acknowledge that some "facts" change as science learns more about the world. Then again, there are those guys that simply will not change their minds just because they think that that would show that they are weak and then they would loose control over the conversation and ultimately you.

 

[dave@aDave]

For my astro telescopes, use 7mm as that is the pupil size for a fully dark adapted eye. Anything larger is wasted, less is dimmer. Now for daylight....smaller size may work because it is brighter; I think would allow some error in eyeplacement; don't know about paralax tho.

Same is for binoculars, 7mm is the practical limit...10mm allows your eye to wander around the eyepiece. More $$ for exit pupil over 7mm is wasted.

Aha!!
That explains why the (almost) standard U.S. Navy binocular was the Mk XLIV Mod 0, 7 x 50 for lookouts. They had a hard life in the submarine service. The binoculars would bang on the ladder steps when the lookouts slide down the ladder from topside when diving. The optical shop on the tender stayed busy. Along with periscopes that somehow got bent over.

 

[Jarhead6870]

You are correct in that the exit pupil changes depending on the magnification you are using. This is why one needs to have an understanding of this principal when setting up the scope for eye relief. I’ve heard too many times that a scope was a poor product because it “tunneled” at high power. This is because the scope was set up improperly and what the shooter was experiencing was the effects of a smaller exit pupil for a given cheek weld and eye relief.

I teach beginning shooters to use the highest magnification when mounting a scope and setting eye relief; this is the smallest exit pupil. After the scope is mounted so the shooter has a FULL field of view with no tunneling or shadow, the exit pupil will only get larger causing the shooter to move his check weld back slightly to avoid scope shadow. This method has worked well for me when introducing new shooters to scopes and how to mount them.

 

[LRH]

I was having a similar question lately and posed the question, does a larger exit pupil mean a better eye box and this is the response from a major manufacturer:

Yes, there is a correlation between exit pupil and eye box. The larger the exit pupil, the more forgiving the eye box will be.

 

[M-61]

I'm 61 years old and the worst guys to argue with are old retired folk, they made up their minds 40 or 50 years ago and you'll never get them to acknowledge that some "facts" change as science learns more about the world. Then again, there are those guys that simply will not change their minds just because they think that that would show that they are weak and then they would loose control over the conversation and ultimately you.

You ever engaged any millennial in a conversation ?

 

[fkimble@charter.net]

How does the light know its going thru a variable power scope? So your friend says the laws of nature/physics are different for variable power scopes?

Frank

 

[Kracken McGraw]

You ever engaged any millennial in a conversation ?

They already have their minds made up in just a few short years and any advice given to them in conversation is just wasted.

 

[NorCalMikie]

Then again, there are those guys that simply will not change their minds just because they think that that would show that they are weak and then they would loose control over the conversation and ultimately you.

Goes for Liberals AND Conservatives also.