Rifle Scopes How big of an advantage are the large objectives?

[xJohnBrownx]

Larger objectives are primarily to allow more light into a scope, they have no affect on field of view or clarity.

Considering glass of equal quality, and given the following-
Objective diameter ÷ exit pupil = magnification
The average human pupil dilates to a max. of 7mm, a scope with a larger exit pupil than 7mm will not appear brighter.

The math works like this-
56mm obj. allows 8.00x magnification without loss of brightness
50mm obj. allows 7.14x magnification without loss of brightness
44mm obj. allows 6.29x magnification without loss of brightness
42mm obj. allows 6.00x magnification without loss of brightness
40mm obj. allows 5.71x magnification without loss of brightness
32mm obj. allows 4.57x magnification without loss of brightness.

Generally less weight & bulk is a good thing for a rifle that is being used in the field.
Also, there can be advantages such as a better cheek weld to mounting a scope low.
Other than to allow a for a larger scope or avoid mirage problems from a hot barrel I can't think of many for mounting higher than necessary.
I suspect very few of people would miss the 1.14x loss of magnification between the 50mm and 42mm during twilight hours.
Am I missing something or could most of get by with something less than the popular 50mm objective?

Maybe it comes down to the ring heights that are available to get the smaller scopes down lower and take full advantage of the smaller size?

 

[jvencius]

Re: How big of an advantage are the large objectives?

quality of the glass comes into play as well--a top quality scope with a smaller objective will outperform a Barska/NCStar/Leapers/etc... with a main lens the size of the Hubble Space Telescope.

 

[xJohnBrownx]

Re: How big of an advantage are the large objectives?

No more opinions?

 

[glock24]

Re: How big of an advantage are the large objectives?

I'm not sure if any actual differences can be seen between a 32mm and a 56mm objective, but it is my understanding that larger objective lens technically do improve clarity.

It is called angular resolution, or the Rayleigh criterion, and the only factor we can control is objective lens diameter.

Personally, I'm a fan of large objective diameters if weight isn't a consideration. I loved my 58mm USO!

But to your point, with quality glass, a smaller objective does the job very well, and it is much more practical for a field rifle. I run a 42mm objective on my hunting rifle mainly because I want the scope as low as possible.

 

[UNCIVILIZED]

Re: How big of an advantage are the large objectives?

It's not a purely direct comparison, but I've spent a good bit of time glassing at dusk, & after dark with 2 different sized pair of Steiners 6x30's & 7x50's.
The first couple of times I was shocked at how much difference there was. Not that I don't love the smaller pair, but there's no comparison between the two.

One other insight. On a good clear day, it's fairly easy to view things at 1.5-2x per hundred yards times the magnification of your scope. IE; viewing things at 1500yds+ with a good 10x scope. But when viewing conditions are crap due to dust, humidity, lighting etc, it seems like the numbers flip. Meaning I'd prefer 1.5x or more per hundred in order to see the target well when the light & or viewing conditions aren't ideal.

I'd say unless you plan to outfit things with NVG, definitely go with the bigger objective for low light work. Height's not really a big issue given the multiplicity of ways to raise the comb.

 

[Radar360]

Re: How big of an advantage are the large objectives?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: glock24</div><div class="ubbcode-body">

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Love it! LOL

 

[Steve**12]

Re: How big of an advantage are the large objectives?

I love my sightron 10-50x60 but as metioned it weighs a ton.