40mm vs 42mm objective scopes

[twoSevenO]

So the 42mm (if my math is good) gives about 10% more area. So should be gathering more light. But Has anyone proved to themselves that it performs better? Is the difference big enough to be noticeable by the average hunters eyes?

A comparable scope in quality to test would be the Leupold Fx3 6x42 against VX3 40mm set at 6x magnification. (I have the former but it can't really compare to my other 40mm which is a Leupold VX1. The FX3 is simply a much better scope.)

Curious if 1. anyone has done Such a test, or 2. people's general opinions on the two very closely related yet different objective sizes, or 3. Any history between the two numbers and how they remained in coexistence without one becoming the official "standard" objective size.

[okas]

that fx 6x42 sucks in the light for most hunting it is great .Due the math here as o too 400 yards all you need for a pie plate shoot .

[Blockcaver]

At its given power and objective lens diameter, a fixed power scope is typically optically superior and probably tougher than a similar quality variable......i.e. 6x42 versus a 3.5-10x40 set on 6X. But most hunters vote for the variable to optimize situations from close in to way out. A bigger objective will be brighter, all else being equal, and you are correct, it is about 10% more lens area in a 42mm versus a 40mm. Can you see an extra 30 seconds or minute near dark......probably.

If the fixed 6X satisfies you, hunt with it and be happy! If I were a rifle hunter, I'd be satisfied with either.

As per objective size, Leupold has standardized around 2-7 x 33, 2.5-8 x 36, 3-9 x 40 (or 50) in 1" variables and 6x36 and 6x42 in 1" fixed power hunting scopes for many years. Lightweights have a smaller 28mm objective in 2-7X and 33m objective in the 3-9X. Bottom line, objectives are available in small to large depending on what you the consumer believe is optimum for your use.

[sheephunterab]

Everything needs to be 100% equal to compare the amount of light that reaches the eye and unless you are comparing the exact same brand and model all things are not equal. Lens quality, coatings and a host of others also play into light transmission. The other question to ask is that if your eye can even utilize all the light being transmitted. A 7mm exit pupil is the maximum usable by the perfect young eye. It's why the 6x42 was a favourite in World WarII. It gives that perfect 7mm exit pupil. But few people have perfect eyes and as we age that exit pupil shrinks, often to 4mm or less so anything more would be indiscernible. If you are worried about the scope being "bright"...I'd worry a lot more about actual light transmission through the lenses....not the size of the exit pupil.

[twoSevenO]

no, not worried about it .... asked more so out of curiosity than anything, as it seems some manufacturers have adopted 40mm (Leupold) as their standard and others 42mm (zeiss) but neither offer an explanation why they have the dimensions they do.

personally, i don't think i could see a difference, even if i had 2 of the exact same scopes fitted with the two different objectives. My eyes simply aren't as picky as some others'.

[sheephunterab]

The Zeiss standard is likely 50mm to be honest just because of all the night hunting done in Europe but for the North American market the 42mm is more practical.

[MRP]

On the diameter 10% more light. But there's a little less glass too.

heres a light performance calculator
http://www.scopecalc.com/