Magnification differences between similar scopes

[Half Fat]

I am wondering, if you had the same make and model of scope, but in different magnifications, say 3-18x and 5-25x, would they look the same at equal magnification? Say you had them both set to 15x, would there be any optical difference between the two? My thought would be that the lower power scope would perform better, but I have no way to test this.

Hoping someone has tested this and can give me some insite

 

[Jahnj0584]

Logically they'd look the same at 8x but if they aren't using the same glass, the 25 could look "better" at 18 then the 18 itself.

Most often I think only the internals are different though. Same glass per product line.

 

[Potashminer]

I am wondering, if you had the same make and model of scope, but in different magnifications, say 3-18x and 5-25x, would they look the same at equal magnification? Say you had them both set to 15x, would there be any optical difference between the two? My thought would be that the lower power scope would perform better, but I have no way to test this.

Hoping someone has tested this and can give me some insite

I had asked similar on CGN some years ago - how do you know that "set to 15X" is really 15? not 13 or 17 - you are "hostage" to marketing of that scope, I think? In like manner, how do you know a 2.5-10 variable is different magnification than a 3-9 variable - which one is "correct"? Not sure that I ever discovered how a "home guy" can verify magnification.

 

[Jahnj0584]

I had asked similar on CGN some years ago - how do you know that "set to 15X" is really 15? not 13 or 17 - you are "hostage" to marketing of that scope, I think? In like manner, how do you know a 2.5-10 variable is different magnification than a 3-9 variable - which one is "correct"? Not sure that I ever discovered how a "home guy" can verify magnification.

Can't you just literally look at the same target with the scopes beside each other? For sure, the numbering are somewhat "nominal" and not as precise as turret clicks, but it is going to be close.

 

[Potashminer]

Can't you just literally look at the same target with the scopes beside each other? For sure, the numbering are somewhat "nominal" and not as precise as turret clicks, but it is going to be close.

Is what I arrived at - which requires you to have both scopes on hand. Which is problematic in many instances. I know for sure that brand "X" and brand "Y" have different height dimensions for "Low", "Medium" and "High" rings - leads to questioning how do I know that brand X is same 3-9 or whatever, as is brand Y - before you buy them, to compare to each other.

That came about when I got a 4.5-14 Mueller scope - how to compare it to a 6.5-20 Leupold? That I know of, was no way that I could verify any number on either scope. Both were "lots more" than I could see with my naked eye - but was not sure how to justify the price difference between them.

 

[grassforbreakfast]

I am wondering, if you had the same make and model of scope, but in different magnifications, say 3-18x and 5-25x, would they look the same at equal magnification? Say you had them both set to 15x, would there be any optical difference between the two? My thought would be that the lower power scope would perform better, but I have no way to test this.

Hoping someone has tested this and can give me some insite

I haven't tested it, but what I've learned from Internet optics gurus is, what matters most is objective lens divided by the zoom power, compared to the average person's max pupil size of 5mm (7mm if you're a youngster). If your 3-18x has a 50mm Objective lens and the 5-25x has a 56mm objective lens then at 15X the 5x25x will be brighter especially in low light conditions. Also on a bright day your pupils may only be 2mm in diameter so you probably won't be able to see a difference between either scopes.

3x18x scope 50mm / 15 = 3.33mm
5x25x scope 56mm / 15 = 3.73mm

Another factor is many scope model are not exactly their stated zoom level so even between the same model family of scopes, there may be differences.

Hope this helps

 

[grassforbreakfast]

how do I know that brand X is same 3-9 or whatever, as is brand Y - before you buy them, to compare to each other.

Hi,

A general way to find out what the actual zoom levels of a scope are, you take the objective size and divide by the published exit pupil. Not many scope companies actually provide the exit pupil info any more and if they do it's only high or low zoom.


For example Burris E1 4.5x14x42 High exit pupil is 3mm and Low exit pupil is 9mm.
42/3 = 14 (what is listed)
42 / 9 = 4.67 (4.5 for practical reasons)

Another is Schmidt and Bender 2.5-10x56 Zenith

High exit pupil 5.6mm and Low 14.1mm
56 / 5.6 = 10
56 / 14.1 = 3.97 ( almost 1.5 zoom higher than listed)

Let's see Trijicon Accupoint 2.5-10x56

High exit pupil 4.32mm and Low 16.26mm
56 / 4.32 = 12.96 (2 zooms higher)
56 / 16.26 = 3.44 (1 zoom higher)

What about trusting a company that lists perfectly matching exit pupil to zoom level ratios? Well they could be correct or they might have just divided the Objective by the zoom level

No name brand 2.5-10x56

56 / 10 = 5.6mm
56 / 2.5 = 22.4mm

Looks like we can't trust anyone's zoom numbers.

Hoped this helped.