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50mm vs. 40mm Objective

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EdSy View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote EdSy Quote  Post ReplyReply Direct Link To This Post Topic: 50mm vs. 40mm Objective
    Posted: May/07/2020 at 05:50
Hi:  This is my first post.  I've been reading the forum for several weeks, while shopping for a better dawn/dusk scope for my deer rifle.  I hunt whitetail deer in the woods from tree stands.  I've used mostly Leupold scops for decades.  They work fine, but recently have wondered how much benefit I might realize if I move up to a 50mm objective.  At the same time, I'd upgrade to a VX-3 or VX-3i model.  I understand exit pupil, and its "shrinkage" as magnification increases for a given objective lens diameter.  Since most of the deer will be at 100 yards or less, having a variable scope set at its highest power is not necessary.  So, my question is: how much brighter would a 50mm set at about 7X be, than a 40mm set at around 5.5X? These magnifications were chosen to realize a 7mm exit pupil in the respective scopes. Many thanks, Ed
-Ed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2020 at 08:03
Light transmission is the advantage of 50mm vs 40mm... under your hypothetical, you would have roughly the same brightness at the higher power with 50mm as the lower power at 40mm... all other factors being equal (glass quality/coatings, design, etc).  You lose some depth of field with the 50mm.   The larger objective will also require a bigger, heavier, less wieldy (to some) scope and can create some issues addressing the scope/rifle.  
For your purposes, the 40mm will probably meet every need.  Remember, numbers on paper do not necessarily translate to visual perception.  Just because numbers are "better" does not mean the eye can perceive or translate it.  

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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2020 at 15:24
There is an advantage to a 50mm objective, but under 100 yards, I do not know if I would necessarily be going bigger for regular hunting hours use.  If you shoot pigs in the middle of the night, that's a different ballgame.

If you are looking to get better performance, I would probably be inclined to stick with the 40-42mm objective and step up to something with higher optical quality.

ILya
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shenko Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2020 at 15:25
In that scenario, the 50mm at 7x will be significantly brighter than the 40mm at 5.5x. For better dusk/dawn performance, go with the bigger objective, and experiment to find out what magnification works best for you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2020 at 16:47
If you use 5.5x with a 50mm objective, you will definitely see a brighter "picture".  At 7x, most will not be able to recognize a difference.  

Here is Leupold's version (since you are looking at their scopes) of it (however, they DO have their numerator and denominator reversed):

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Travis299 Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2020 at 07:46
Semper Fi
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