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Binoc Light Brightness vs Riflescope

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/05/2007 at 20:58
sage1 View Drop Down
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I'm hoping one of you more experienced optics guys can help answer a question for me. Tonight I was out until dark trying to call in a few coyotes (no
luck). When the light was low I compared my binocs (Leica Ultravid 10x42) to my Zeis Conquest 3x9x40 rifle scope fully expecting the binoc's to be much
brighter in the low light. Surprisingly the rifle scope was much much brighter. I thought the light gathering capabilities of the Leica's would far surpass
the scope but not so. If there's a technical explanation of why a scope would be brighter than binoculars can someone explain it to me ?

My thanks in advance

Sage1
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/05/2007 at 21:24
lucznik View Drop Down
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I can think of two things that would at least partly explain what you are seeing.

 

1. Your binocular has an exit pupil of 4.2 mm.  Your riflescopes exit pupil ranges from a low of 4.44 mm to a high of 13.33 mm.  Higher exit pupils generally equal more light. (Some variations can/will be seen depending on the type, the quality, and the quantity of the lens coatings used.)

 

2. Some of what you are seeing can be chalked up to a simple optical illusion.  Take a paper towel tube and look through it and you will see that the image you see through this "optic" will appear brighter than the same scene with the "naked eye."  This is due to the fact that the cardboard tube limits the field of view and creates a dark-tunnel effect that makes the viewable image look brighter because of the contrast between it and the tube's dark edges.  Because riflescopes (generally) have much narrower fields of view than binoculars (largely due to their use of only one eye) they are much more susceptible to this illusion.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/05/2007 at 21:53
Roy Finn View Drop Down
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What lucznik stated is right on the money as usual. A simple way to make things comparative is to recreate the scenario with your Conquest set at 9 power thus creating closer exit pupil values. I am betting in that comparison that the Leica binocular will allow you to see more than the riflescope will show, two eyes vs.one.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/05/2007 at 22:49
sage1 View Drop Down
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Thanks guys, that makes sense. S1
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/06/2007 at 08:24
SAKO75 View Drop Down
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I have compared my 8x42 ultravids to a diavari 2.5-10x50 and a 3-9x40 conquest and its not even close, the ULTRAVID blew them both away
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/06/2007 at 15:15
sage1 View Drop Down
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Sako

 

What the difference was is the scope was on 3x and the binocs are 10x. If the scope had been on 9x the exit pupil size would have been closer to the exit pupil size of the binocs and most likely the scope would have been darker than the Ultravids.

 

S1

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/06/2007 at 20:05
tbone1 View Drop Down
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This is a classic example of how side by side testing is sometimes flawed.  I agree with lucznik on this.  I guess it is an optical illusion.  All I can tell you is that I haven't compared them side by side to see which one looks brighter, but I have been in numerous hunting situations in low light (too many to describe) in which I have been trying to take an animal that I can see fairly well through the binos that I couldn't see at all through the scope (Leica binos vs Leupold, Conquest, Swarovski.)   I can assure you that in a hunting situation the binos will outperform the scope regardless of how bright they may "look" in side by side testing.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/07/2007 at 07:54
ND2000 View Drop Down
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I totally agree with tbone1 on this.  I've had more occassions than I care to remember where I could see my target through the binoculars but not via the scope, or certainly not as clear.

 

ND2000

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2007 at 13:07
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Assuming similar exit pupils I would have expected binoculars to do better than a scope, as two eyes are better than one, but there are other differences.

 

I don't know what model years you have but current, good rifle scopes could be better than older binoculars, especially some of the older roof prism models.

 

'Brightness' is a perception, which is why it's nice to see wavelength vs transmission charts of optics. Zeiss acknowledges that they have elevated blue transmission, which could often end up appearing brighter even if it's not.

 

  

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