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20mm vs. 50mm

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/10/2007 at 17:36
tucker View Drop Down
Optics GrassHopper
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You guys gave great advise last time so I'll fire off another one!!!   How much difference is there between a 20mm and a 50 mm scope...as far as letting light in.  I worry about scopes much under 40mm because I fear I won't be able to see well thru them the last few minutes of legal time.  Please include the smallest objective that ya'll would use for hunting around dusk.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/10/2007 at 17:42
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Optics Master
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The formula for the area is area = pi X radius squared but that is only one factor in light transmission, you really need to do a side by side comparison in low light, the quality of the scope makes a difference with small objectives.
 
Duce Smile
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/10/2007 at 17:52
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Optics Jedi Knight
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depends on the magnification
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/10/2007 at 18:09
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Optics Master
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Heres a handy chart to give you a quick overall idea. First depending on your age and general eye condition your exit pupil size will be 5 to an absolute best of about 7. Unless you're quite young figure about 5-6 now look at the objective diameters you're comparing. It shows how much power you can use for your eyes exit pupil. Now all things being equal the higher magnification will allow you to see an object in low light better simply because its larger in the sight picture. This of course has to take into account that you can hold the rifle and scope steady at higher power. Now the brightness and resolution gets mixed in by taking into account the actual optical quality of your chosen scope. Not a simple one answer fits all kind of thing.....


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/11/2007 at 06:20
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Optics Apprentice
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If you take two of the same scope models, but in a 3-9X40 and a 3-12X56, the 56 will be brighter at higher powers.  When the exit pupil is above 7 on both scopes you will not be able to tell a difference in brightness.  When you get above 5.5x on the 40 you will see that the 56 is brighter on up to 8x.  8x is your best shooting power on the 56 and 5.5x is your best shooting power on the 40 as fas as brightest high magnification.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/11/2007 at 14:51
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a 3-9x40 is plenty of 'light' if you keep the magnification around 5 or 6 when it gets dark.
 
if you are hunting longer ranges where magnification is important, go 50-56mm if you want the most light - BUT it's a huge objective lense that may look funny on your rifle.
 
J
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