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Hi, new member. And a questions.

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2010 at 09:45
Dunc View Drop Down
Optics GrassHopper
Optics GrassHopper


Joined: July/11/2010
Location: Buckinghamshire
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Hello all.  Fairly experienced shooter (40+ years!!!) but have an optics question that I can't get an answer to so hope you don't mind my first post being largely a question! Howdy
 
I use a high powered air rifle for squirrel shooting in a wood - a rimfire wouldn't be safe as most of the shots are into the tree canopies.  And as I shoot in a wood, light gathering is important as the most productive times for me are dawn and dusk.
 
But as most shooting is at relatively short range eg 15-20 yds, my scopes are always on minimum magnification ie x3 or x4 depending on scope.
 
My question is however, assuming the scopes are identical and the lens quality and coatings are the same etc etc, will I get more light and hence longer shooting at dusk with a 50mm objective lens than say a 40mm lens?  Reason I ask is that 4mag divides into 40 10 times and by some rules of thumb, this is greater than the exit pupil so is there any need for 50mm?   However, intuitively, at night, surely you want to grab all the light you can get?
 
Thanks in advance!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2010 at 09:59
stork23raz View Drop Down
Optics Journeyman
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If everything about the scope is the exact same quality,  then the larger the objective then the more light should be allowed in therefor the brighter. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2010 at 10:23
ckk1106 View Drop Down
Optics Master
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I don't think the 50 mm will be any brighter than the 40 mm at 3 or 4 X.  I think larger than 7 ish exit pupil is just wasted.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2010 at 10:30
pyro6999 View Drop Down
Optics Retard
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OT TITAN

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Originally posted by ckk1106 ckk1106 wrote:

I don't think the 50 mm will be any brighter than the 40 mm at 3 or 4 X.  I think larger than 7 ish exit pupil is just wasted.  

exactly, if we were talking about 14-24x then we would be cooking with gas.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2010 at 10:47
Dunc View Drop Down
Optics GrassHopper
Optics GrassHopper


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Originally posted by ckk1106 ckk1106 wrote:

I don't think the 50 mm will be any brighter than the 40 mm at 3 or 4 X.  I think larger than 7 ish exit pupil is just wasted.  
Thanks all, so far.  And this (above quote) is exactly the issue.  Although just doesn't 'seem' right when we're in darkish conditions! 
I could save some useful weight by changing my Walther 4-12 x 50 for something in the 40mm range.
Thanks again.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/23/2010 at 16:23
stickbow46 View Drop Down
Optics Master Extraordinaire
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+1 with ckk
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/03/2010 at 05:57
billyburl2 View Drop Down
Optics Master Extraordinaire
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The reason an exit pupil above 7mm is "wasted" is the iris of our eyes only open to 7mm. Thus any light coming through the exit pupil of the scope can't be transmitted through our eye.
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