Excellent Article on Rifle Scopes and Their Brightness

[35 Whelen]

Thought you fellas might enjoy this article on rifle scope brightness. It dispels a lot of myths. For those who've never heard of John Barsness, he is in my opinion without equal when it comes to writing over scopes, rifles, calibers and hunting.

35W

 

[Tract Optics]

Read that one a while back. Great info in there on the facts and fallacies.

 

[chicharrones]

Thanks for the link.

One thing that I find interesting is about the comparison of exit pupil to the size of a human's pupil. Even if my pupil can only reach 5 mm or 6 mm, due to being middle aged, I still find a scope with an exit pupil larger than 5 to 6 mm easier to use.

Most every thing I read suggests that exit pupil on a scope that is larger than my eye's pupil is a waste. But I don't think so. I think a larger exit pupil gives my eye more room for misalignment errors when shouldering a gun quickly. A couple extra millimeters of head (eye) alignment fudge factor is something I prefer.

 

[WelshShooter]

Thanks for the link.

One thing that I find interesting is about the comparison of exit pupil to the size of a human's pupil. Even if my pupil can only reach 5 mm or 6 mm, due to being middle aged, I still find a scope with an exit pupil larger than 5 to 6 mm easier to use.

Most every thing I read suggests that exit pupil on a scope that is larger than my eye's pupil is a waste. But I don't think so. I think a larger exit pupil gives my eye more room for misalignment errors when shouldering a gun quickly. A couple extra millimeters of head (eye) alignment fudge factor is something I prefer.

You're absolutely correct! If the exit pupil of the image is 10mm and your pupil diameter is 7mm in low-light then you have some additional room for misalignment. If the exit pupil was 7mm under the same circumstance, then you would need to keep good alignment.

This is why your head position is critical on variable power scopes when you increase the magnification compared with reducing it.

The article isn't 100% wrong in saying anything above your pupil diameter is a waste. If you are looking to spend more money on a scope purely for increasing brightness at low light conditions, then you won't get much more of an improvement of a 10mm vs a 15mm if your pupil diameter is 7mm. That money can be better spent on better quality glass rather than higher exit pupil size.

 

[MCMXI]

Based on that article the Leupold FX-3 6x42mm should be one of the greatest deer/elk hunting scopes on the face of the earth. With fewer lenses than a variable and a fixed exit pupil of 7mm it should have excellent clarity in low light and enough magnification to make ethical hits out to 600 yards. If only it had an RZ reticle rather than the long range duplex, but at least the custom shop offers BDC adjustments.

 

[jmr40]

The size of the exit pupil is simply the diameter of the beam of light that makes it to your eye. How bright that beam of light is is determined by the quality of the lense. A high quality scope with an exit pupil of 5mm will be brighter than a low quality scope with an exit pupil of 7mm.