scope size 40 mm vs 50mm

I prefer the 40....helps keep a "cheek weld" on stock, at has less effect on trajectory. Also, lightens the scope, a little. A 40 with good glass, generally, can have you hunting before and after legal hunting hours in most states! memtb

Bigeclipse said:

I am NOT an expert but I think it will depend on some things. Is weight a concern? All other things being equal, 50mm is typically heavier. Do you have an adjustable cheek rest? 50mm scopes typically need a higher comb height than non-adjustable run of the mill stock can provide. If neither of those things are an issue, again, all other things being equal, 50mm scope will typically have better low light capabilities than 40mm. I would rather have a higher end 40mm than a lower end 50mm scope with regards to clarity and low light conditions because the glass in the higher end 40mm is likely that much better.

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How 'bout higher end 50 over a higher end 40?

I will take a quality 50 over a 40 any day. Good optics that provide low light ability and larger field of view is more important to me than saving a couple of ounces.

I'll match my Leica 42 mm against any 50's.

Peddler 76 said:

I'll match my Leica 42 mm against any 50's.

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S&B PMII 4-16×56 Ultra Bright? Tangent Theta TT315M or TT315P 3-15×50? Hensoldt ZF 4-16×56? I'll take that bet.

If it takes double the money have at it. You won't see that much difference.

Canhunter35 said:

I've noticed that with my mark 4 and other leupolds, they do well in low light. But the example I related was a 30 year old 3-9 leupold was outperforming an s3 sightron. It was pretty dark though as we were hunting beavers.

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The older model S3 was decent but just a cheap scope. I had several of them because I had too many guns that needed an upgrade and at the time couldn't afford any better.

I equate them to the VX2 with the same objective.

Peddler 76 said:

If it takes double the money have at it. You won't see that much difference.

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You certainly will in those critical few moments of last light after the sun drops below the horizon and in the early dawn before it breaks the horizon at least with quality glass.

You simply have over 20% more surface area and hence that much more light being collected and transferred to the magnifier.

The higher the magnification the more light required for good resolution. This is the same reason you have to use an alternate light source in microscopy as you increase magnification.

Peddler 76 said:

I'll match my Leica 42 mm against any 50's.

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The physics simply don't allow for this.

Peddler 76 said:

If it takes double the money have at it. You won't see that much difference.

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Just calling your bluff. I take my rifle optics very seriously.

To be honest, I think my S&B PMII 3-20×50 is ridiculously bright. It is so good at gathering light, it is fully capable of seeing at full night with very little moonlight. High end optics definitely show their benefits in the worst conditions.

Understood, but comparing 56's is a bit unfair.

Peddler 76 said:

I'll match my Leica 42 mm against any 50's.

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You'll loose.

Peddler 76 said:

Understood, but comparing 56's is a bit unfair.

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You're the one who said you would put your Leice w. 42mm objective against any of the 50s!

I would still put my Tangent Theta 3-15×50 TT315M, Premier Heritage Light Tactical 3-15×50, or S&B PMII 3-20×50 against a Leica w. 42mm objective any day for light gathering.

Light transmission rating per manufacturer claim/exit pupil (objective ÷ magnification):
Leica has a 92% w. 14.3 exit pupil @ 3x
S&B has a 96% w. 16.6 exit pupil @ 3x
Tangent Theta has a 96%+ w. 16.6 exit pupil @ 3x
Premier Heritage 94% w. 16.6 exit pupil @ 3x

Add an extra almost 30% of light gathering surface over the 42mm (1963 @ 50mm vs 1385 @ 42mm in sq/mm)

Plus, you generally get a slightly wider FOV with 50mm objectives over 42mm objectives.
Leica FOV @ 3x=43.6' (45.9' @ 2.5x)
S&B FOV @ 3x=46.7'
TT FOV @ 3x=45.7''
Premier FOV @ 3x=42.2' (less than Leica)

I am not saying Leica scopes are not fantastic. I have shot behind a couple of them at the range. Very clear and bright. Leica scopes weigh less than the others I compared to. Almost 20-45% less. That is big for a lightweight mountain rifle.

deaner 20 said:

just want some opinion on what hunters thoughts were on what and why they prefer .thanks

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Peddler 76 said:

Understood, but comparing 56's is a bit unfair.

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IMO, it's also unfair to coompare a 40mm to a 50mm scope....at least in a technical sense. If you back to the basic question from the OP, perhaps it's best to give the basic explanation of the difference. Assuming that glass quality and magnification setting is "equal", the larger the objective, the greater the size of the exit pupil, and the light delivered to the eye. At 10x, a 40mm scopes exit pupil will be 4mm(40 divided by 10). A 50mm will be 5mm, a 20% increase in light delivered to the eye. It's important to note that the size of a human pupil expands to 5-7mm. Any addition light produced by larger exit pupils from the scope will not be accepted by the eye. In the above comparison a 50mm will provide the eye with more light gathering ability and very likely be noticeable in low light conditions. As a side note, the eye box in this example will be larger as well. At higher powers at longer ranges in low light, the difference in light gathering can be more dramatic. At 15x, the exit pupil of a 40mm will be 2.7mm, the 56mm will be 3.7mm, almost 40% greater light gathering ability that the eye(5-7mm) can take advantage of. Of course, other factors can come into play such as glass quality, cost,construction, size, weight, etc, which results in the shooter making trade-offs. All things being equal, within the boundaries of the human eye, a larger objective lens will gather more light. Apologies for the long winded explanation.