Rifle Scopes Basic scope question...

[AtownBcat]

I am a hunter first who has branched into long range shooting. I am currently using a NF 5.5-22x56. I had a VX-III 4.5-15(i think it was a 4.5 could have been 3.5) and before that the old stand by 3-9 VX II, anyway while I would say the glass clarity is either equal or slightly leans toward the NF I would say that being able to see in low light actually was quite a bit better with the Leupolds. Is this by design or is this just a side effect of the higher magnifacation? Would I need to compare a 15x NF to a 15X Leupold?

 

[jonaddis84]

Re: Basic scope question...

Compare at the same magnification, doesnt have to be the same max power scope, but compare the NXS on 14x to the Leup on 14x, or both on 10x etc.. More magnification means more light is required, thats why objectives almost always get bigger as zoom levels go higher.

 

[Redmanss]

Re: Basic scope question...

If you were on a different magnification level, your exit pupil diameter size was different, thereby allowing less light through the scope itself. Light transmission is a function of glass quality level, but exit pupil diameter has a much greater effect on it.

The basic exit pupil diameter formula is: objective dia/mag level = exit pupil diameter

Your 5.5-22x56 NF for example:
56mm/22x=2.545 (2.5mm)
56mm/5.5=10.181 (10.2mm)

It's just one thing to be considered when selecting a scope, especially if you're planning on shooting in reduced lighting.