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Help Me Decide Between Kahles 8X42 and 10

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/03/2006 at 17:35
Capphd View Drop Down
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I have read and researched this decision ad nausem.  I have read every post on this forum that has to do with the models I considered.  I have narrowed it down to the two Kahles models.  I use my binos for deer hunting in north Louisiana and in the Texas Hill Country.  Low light performance is important.  Also, I have no trouble holding 10X binos steady.  Will I lose much dawn and dusk performance if I go with the 10X?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/03/2006 at 18:54
lucznik View Drop Down
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Actually, you will quite possibly gain low-light viewing ability with the 10X.  The exit pupil (calculated by dividing the objective lens diameter in mm by the magnification power) is the much touted term in relation to overall light "transmission" and a lot of people go strictly by this figure. Of equal (and possibly even greater) importance is what's known as the "Twilight Factor." It is calculated by taking the square root of the sum of magnification times the Objective Lens diameter in mm and is supposed to indicate a binoculars theoretical level of performance in low light.

 

Thus you get:

 

Exit Pupil

10X42 = 4.2

8X42 = 5.25  (Advantage to the 8X)

 

Twilight Factor:

 

10X42 = 20.49

8X42 = 18.33 (Advantage to the 10X)

 

Which one of these two factors is really more important to measuring low light ability is up for debate. However the Twilight Factor (in theory) was developed specifically to represent a binocular's (or other optic's) relative low-light performance level and so, should probably be given some serious weight in the decision.  I personally think that they are both important and that each has merit.

 

In reality, assuming you are buying a good, high quality binocular (and the Kahles definately qualifies in spades) I doubt that one or the other would ever provide either measurably superior or inferior performance at dawn or dusk under any conceivable hunting situation. Certainly not enough to warrant choosing one over the other.  Neither my  8X Pentax nor my 10X B&L demonstrate any noticable low-light virtues above the other.

 

I think you might be better off focusing on issues such as FOV (the 8X will be wider, but by how much and do you care are different issues) and whether or not you like to "be" just that much closer to the object in question (advantage to the 10X.) And possibly even cost.

 

In the end neither one will prove to be a mistake and you will provide excellent optical performance over any and every field conditions imaginable.

 

 



Edited by lucznik
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/03/2006 at 19:18
Roy Finn View Drop Down
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Capphd, lucznik pretty much summed it up and if it were me I would go with the 8x42 over the 10x42 because it will be easier to hold steady and it will be brighter. The optical terms "relative brightness" and "twilight factor" are confusing in that the 8x42 will have a higher relative brightness factor than the 10x42 and the 10x42 will have a higher twilight factor than the 8x42. The 8x42 will have a brighter image. The 10x42 will have a larger image. See what I mean, confusing isn't it. Also, if you were to give weight to these terms which are constant, you would (could) falsely conclude that a, for example, Simmons 10x42 is brighter than a Zeiss FL 8x42. I am not trying to diminish what lucznik is offering. I would just get the 8x42 and be done with it.

 

 



Edited by Roy Finn
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/04/2006 at 00:07
chasseur106 View Drop Down
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I agree, though I don't do all the calculations that other guys might do on these binoculars to determine what I want to buy.  The reason I say go with the eights (8X42mm), is that you will be able to pick up game that much quicker with the 8X42mm's because you will be able to see more of the woods. 

            If your only desire is to see more of the animal, then I would leave the rifle at home, and just watch deer to your heart's content.  I am not being sarcastic here.  I am trying to make the point that, like a rifle scope left set on too high of a magnification, a pair of binoculars can make finding game difficult at ranges closer than 300 yards if you have to scramble with the high power optics through lots of ground clutter, before seeing the animal.  I don't know about hunting competitiveness in Louisiana, but here in PA, you don't always have a great deal of time from the point of seeing the animal to the point of shooting at the animal.  And most areas good for deer are great with ground clutter and so I don't personally think that seeing with 10 powers are better than seeing with 8's, because of this.  I would personally leave the 10's for a hunt out west where you have a great deal of terrain to cover and very little if any trees and forests to pierce through with binoculars.

         Do you get my drift?  I hope that this helps you in your decision.

                 Scott

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/04/2006 at 08:36
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I hunt in North LA and used to hunt the Hill Country a lot.  I never felt like I needed 10X, but there have been lots of times I was glad I had the field of view of the 8X.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/04/2006 at 09:30
Capphd View Drop Down
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Great information, guys.  I really appreciate it.  You made my decision easy.  I decided to go with the 8X42.  I called SWFA to order a pair in Loden Green and they were backordered.  I was able to find them elsewhere, but I hated that.  I really like doing business with SWFA.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/04/2006 at 10:35
lucznik View Drop Down
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Not that it matters to your question now but:

 

Roy's makes an excellent point about using the equations for theoretical performance and applying them to binoculars of different makes (i.e. Simmons vs Zeiss, etc.) These equations truly only represent an optic's theoretical performance level and do not take into account build quality, or the type, quantity, & quality of lens coatings, etc. all of which dramatically affect the optic's abilities and thus value. In fact, despite what the equations would seem to indicate on the surface, I would rather hunt with an 8X20 Zeiss, Leica, Swarovski, etc. than a 8 or 10X42mm (or even 50mm+)Simmons, Tasco, Barska, etc. any day of the week (and twice on Sunday.)

 

When using these equations the first you must understand that they apply only to an optics theoretical performance and then you must also understand that they only apply when comparing optics of equal quality.

 

As far as the 8X vs 10X issue; I don't find that I can hold my 8X better (more steady) than my 10X but that may be because the 10X is a porro prism and has different ergonomics. I hunt with some people who swear by their 8X and others who wouldn't be caught dead without their 10X.  Actually, if I could trade away my 8X DCF WP and get one in 10X (or better yet a 10X Discoverer,) I would do it. This is not because of  any defect or lack of optical or build quality in the binocular itself but, I hunt out west and have come to really appreciate that little bit of extra magnification. In the end, as long as you have made your choice based on an honest appraisal of what you think matters most to you, I don't think either is a mistake. 



Edited by lucznik
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: January/08/2006 at 08:54
gremlin View Drop Down
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I love the dialogue and find merit in everybody's points.

Which means...

"8x Versus 10x" discussions are pretty much the same as .270Win vs. .30-06 discussions.  Everybody's always right because they make a decision between two excellent choices.

But I still love the discussion.

Just my two cents.
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