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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/13/2012 at 20:31
matchetman View Drop Down
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Ok, currently have a leupold vx ii 3x9x50. Looking for something to go on a .280 with the main purpose of being able to see in lower light situations. Is the zeiss 50mm conquest worth $200 more than the 40mm objective if lower light conditions is the main purpose of my upgrade?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/14/2012 at 00:52
Alan Robertson View Drop Down
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The 50mm will buy you equal low- light performance with a 40mm, but at a higher magnification. If both were 3-9, as example, at 3x, they both have more visible light available to the eye, defined as exit pupil, than the human eye can use.
Exit pupil is the objective lens diameter divided by magnification. e.g. a 40mm obj. lens/8x=5 (exit pupil), a 50mm divided by 10x= 5.
The best (youngest) human eyes can make use of the light available from an exit pupil of 7. Old guys like me lose out and can maybe see only up to 5 or so.

Larger exit pupil also gives you better 'eyebox',  or a less critical eye position when looking through the scope. Greater exit pupil also translates into wider field of view.

The quality of the lens coatings (probably, the glass itself, also) means that a VX3 or Conquest will be brighter than a VX-II at equal magnifications.
Bushnell Elite 4200s, Sightron Big Skys as well as a few other scopes in the same price range are as good as the VX3s and Conquests in low light.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/14/2012 at 19:03
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+1 well said AllenExcellent
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/14/2012 at 20:20
matchetman View Drop Down
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Ok, in laymens terms, how many more minutes at dusk will the conquest 3-9x50mm give me thanthe conquest 3-9x40mm?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/14/2012 at 20:44
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Both the same but you would be able to keep the 50mm on a higher magnification. Not worth 200 bucks to me and plus you have to mount it higher. Which makes a difference to some.

Either way you are upgrading to better glass and will be better off.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/14/2012 at 20:57
Gil P. View Drop Down
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So with the 40mm to get a 7mm exit pupil you can have your scope set at a max of 5.7X. With the 50mm you can have it set at 7X. It wont be very different. I think the 40mm would be fine unless you want to mount your scope higher like RotoReuter says.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/15/2012 at 00:19
Alan Robertson View Drop Down
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Originally posted by matchetman matchetman wrote:

Ok, in laymens terms, how many more minutes at dusk will the conquest 3-9x50mm give me thanthe conquest 3-9x40mm?
In layman's terms, NO MORE MINUTES, if both have magnification set to have enough light coming through them- "exit pupil"- that your eye needs.
The only difference is that the 50mm will be able to use a slightly higher power setting to get the same amount of light through it than the 40mm, but that's it... the 50mm can use a bit higher magnification to see the same thing.

 If you have both scopes set on the lowest power, they'll both perform the same. If you have them both cranked all the way to 9x, they both become unusable because there won't be enough light getting to your eye to even see the target.

@ lowest power:
40mm/3x= 13.33 50mm/3=16.66 exit pupil... both are providing more light than you can see, since the human eye can only use light from 7 exit pupil.
At 3x mag, if you had a 24mm objective or a 56mm, there still wouldn't be any difference because there would be more light available than your eye could use.

@highest power:
40mm/9x=4.44   50mm/9x=5.55
As you can see, neither performs at it's best in low light at the highest power setting.

Gil P already did the math and showed the maximum power setting where each scope has it's maximum useable exit pupil.
He said: "So with the 40mm to get a 7mm exit pupil you can have your scope set at a max of 5.7X. With the 50mm you can have it set at 7X. It wont be very different"

Both scopes have maximum and equal light with the 40mm set at 5.7x and the 50mm set at 7x.
Below that power setting, there isn't any difference in performance. Above that power setting, and you might not even see the target, because there won't be enough light getting to your eye.

Are you starting to see how it works?

Here's another real- world example:
I have a 15-65x65mm telescope. I can spot a dim star at lowest power and try to zoom up in power to get a better look at it, but at some point, there isn't enough light coming through the 'scope to even see the star anymore, even though the magnification is greater, because I've diminished the light below the exit pupil my eye needs to see the star.

Hope this helps...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/15/2012 at 21:40
matchetman View Drop Down
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Cool. Thanks for the info.
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