opinion on light transmission on scopes.

[keyway]

For hunting coyote before daybreak does the 50mm objective scopes
actually have any great advantage over a 40mm ?

[Zachary]

Optics quality being the same, the answer is yes - but only if the magnification is high enough to warrant it.

For example:  If you have a 50mm scope set at 10x, then the exit pupil is 50/10=5mm.  If you have a 40mm scope, you can achieve 5mm at 8x.  If you have a 40mm scope and you set it at 10x, then the exit pupil is 40/10 = 4mm.

The human pupil opens usually no more than about 4mm or so, which means that you can use a 40mm scope and set it at 10x to get pretty much the most that your eye can use anyway.

Now, if you have a 50mm scope and for some reason you want to crank it up to about 14x, then you will have an exit pupil of 50/14=3.57mm.  If it was a 40mm scope, then it would be 40/14=2.85mm.  That means that a 50mm scope would give you a greater pupil size at 14x, and thus more light to your eye.  However, how often is it that you will be using a scope at 14x?  Not often.  Not even for coyote hunting, but if you need to, then a 50mm would be more "useful."

Now, that said, I also like 50mm scopes for another reason - eye alignment.  Just because an exit pupil may be more than 4mm doesn't mean that it is a complete waste.  Rather, if you exit pupil is say 4mm, but the scope at a particular setting gives you, say 6mm, then it is easier for your eyes to align with the scope.

Again, it all depends on what magnification you use.  The bottom line is it is much better to get a 40mm scope with high quality glass, than it is to get a 50mm scope with cheaper quality glass.

Zachary

[keyway]

Thanks for the information Zachary. You confirmed what I suspected. I just purchased a 204 Ruger bolt action, the clerk tried talking me into
purchasing a 50mm scope for it. I told him that II have a brand new Leupold VX-III 3.5-10 to put on it and tried to sell me a 4.5-14x50. I am
not a magnification freak but the 14 power would be nice on this gun for say a 250 or 300 yard shot. I didn't think the 50mm was nesicary because I usually have the scope at 6power or lower. Thanks for the reply.

[Zachary]

It's funny how 20 to 30 years ago most big game hunters had fixed 4x scopes on their rifles, and varmint hunters had fixed 6x, and they were just as successful getting game as hunters are today.

Today, we have all been taught to believe (including myself) that you must have a 2,500x - 10,000x - 100mm scope to be a good varmint hunter.  That just ain't so.  Granted, I personally generally like higher magnification scopes, but I have realized that I was sucked into the hype that has brought on over the last 15 to 20 years.  I used to think that a 4x-16x scope is perfect for everything because 4x is low, and 16x is great for the shooting at the moon.  Actually, I still think that I am right, but it all comes down to weight and length and extra price.  I may use my 16x scope at full 16x at the range, but I never use it that high when hunting, so what's the point?  You really should use a rifle scope as a spotting scope - especially when the gun is loaded.

Granted, I am not going back to the other extreme of getting a 1.5x-4.5x (although I did for my .375H&H but that's an exception because you must have low magnification on such a big gun shooting dangerous big game up close), but the 3x9ish range scope really is all any big hunter needs - even for varmints.  Unfortunately, I still have some hype left in my blood  so I'm gonna at least keep the higher mag scopes that I have.

Zachary