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ED glass vs. other features

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/29/2009 at 15:39
jonoMT View Drop Down
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Seems from what I've been reading and the (limited) comparisons I've made between optics that have ED glass to others that ED should be a higher priority than other features. In other words, having a lower magnification ED bino or scope would be better than getting an optic with more magnification or a larger objective. Wouldn't it be correct to assume that combining lower magnification ED optics with a greater exit pupil and less susceptibility to trembling or mirage (as well as lower weight) might yield better results in the field?

For example, compare these two Kowa models, the 60mm TSN-603 and the 82mm TSN-82SV (both with the TE-9Z eyepiece). They are $25 apart ($1040 and $1065, respectively). The 603 weighs half of what the 82SV does and has Kowa's XD lens coating, which the 82SV does not. Eye relief is the same. FOV is slightly better in the 603. Length is 12" vs. 15". The 82SV has a max. exit pupil of 3.9 vs. 3.0 for the 603. I'm wondering how much the XD lens coatings make up for the 25% less exit pupil. As far as weight and length go, there's no contest. I'd consider taking the 603 backpack hunting but the 82SV weighs over 3 lbs.

Here are direct links to compare features:
http://www.kowa-prominar.com/product/spotting/tsn600/index.htm
http://www.kowa-prominar.com/product/spotting/tsn82sv/index.htm



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/29/2009 at 17:52
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Well first, XD (or HD, or ED, or whatever moniker a given manufacturer is using) is not a system of lens coatings.  It is the actual type of glass being used in the lenses' manufacture. 

Second, the use of such glass does not increase the amount of light that the optic "transmits" through the system.  It simply allows for better control of that light.  Thus, while image quality and fidelity are somewhat improved, brightness is not. 

Because of this, you are really trying to make an "apples to oranges" comparison.  ED glass comparisons can really only be fairly and objectively made with units of like-specifications and quality.  For example, a 60 mm HD Swarovski is certainly better than the non-HD version of the same or other similarly-sized non-HD scope.  However, is it better than the non-HD 80mm Swarovski spotter?  That's going to be tough to evaluate as the 80mm lens, even without HD glass, is still going to be significantly brighter and have a better theoretical resolving capacity (due to its larger objective lens) than the 60mm scope.  Thus you are trying to compare the relative value of a single item within a cohort of products wherein you have the unmistakeable influence of a relatively large number of variables with which to contend - a situation which the scientific method will tell you is the very hallmark of illigitimacy.

So too with the 50mm class of scopes.  The Nikon ED50 is the clear frontrunner in terms of image quality from such tiny scopes and in bright light it even holds its own against much larger scopes, even ones with ED glass.  But bring on twilight and/or some less-than-favorable weather conditions and these tiny scopes just don't have the "light gathering" capacity to (optically) compete directly against larger scopes.  When you're looking at low-light performance, there just is no substitute for exit pupil.

Objective, verifiable, legitimate comparisons of 80mm vs. 60mm vs. 50mm scopes are pretty much limited to discussions of size, weight, cost, and overall utility.  Discussions of the relative value of HD-type glass must be restricted to comparisons of otherwise-similar scopes in order to remove any bias that might be introduced by other variables.    
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/29/2009 at 18:58
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Good post, lucznik!

Jon,
From your post, it sounds to me that you value a lighter, more compact scope anyway.  I think the 60-65mm spotters are a good compromise between the handiness and "packability" of a small scope and the light transmission and resolving power of a big objective scope.  I truly don't think you will find one of the better quality 60mm class scopes  lacking in image quality in any meaningful way, and the Kowa Prominar certainly competes with the best.  In low light, even the huge 80mm class scopes have tiny EPs beyond 40X -- at or below 2mm.  Everything is a tradeoff.  To gain one advantage, such as light transmission, you sacrifice another, such as increased mass.  If you plan to haul your spotter around a lot and still want top drawer image quality, a 60mm class HD/ED/APO spotter is a good way to go.


Edited by RifleDude - July/29/2009 at 19:02
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/30/2009 at 22:20
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lucznik, I could have obviously made a comparison between HD and non-HD versions if I'd wanted to isolate down to one variable, since there are numerous examples of scopes and binoculars that come in either. However, I am trying to gauge whether HD glass in a scope with a smaller objective compensates for the loss of exit pupil, i.e. is a sharper, dimmer image better than a blurrier, brighter image, and pointed out that the smaller scope has many advantages, particularly in size and weight. Perhaps since Kowa glass is so good in general, its non-HD 82mm option might still outshine the 60mm scope in resolution as well as, most certainly, brightness.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 08:52
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jonoMT, 

Sorry, I apparently didn't answer you question as well as you would have liked.  My bad. 

Originally posted by jonoMT jonoMT wrote:

I am trying to gauge whether HD glass in a scope with a smaller objective compensates for the loss of exit pupil, i.e. is a sharper, dimmer image better than a blurrier, brighter image
  If you were to compare two scopes like the 50mm Nikon ED50 to a non-ED 80mm Barska scope, then the answer would be, "it might."  But, that's just because Barska is generally such total crap in the first place that even your naked eye is probably better. 

The differences between the image from two otherwise-equal-quality scopes wherein the only variable is that one uses HD glass and the other does not are not all that great.  They are visible to be sure, but they are still quite small.

The HD glass does help to improve the scope's resolving performance, but still, only to get closer to the theoretical maximum resolving limit dictated by the objective lense's size - which is still going to be significantly lower than that of a similarly-high quality scope with a larger-size objective. HD glass is good for enhancing the already good properties of a particular scope's design, not for making a small scope perform equal to a large scope.  

There just is no substitution for exit pupil.

This is not to say that a scope with a smaller objective will not serve your specific purposes.  It very well might, depending on what you are expecting it to do. And ED glass in that scope will help it to perform at its highest potential.  It just won't make your 60mm scope (optically) perform as well as an 80mm scope.



Edited by lucznik - July/31/2009 at 09:12
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 10:09
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What the ED/HD/APO glass does is reduce or eliminate chromatic aberration or color fringing.  This provides a slightly sharper, cleaner image with better detail resolution.  It does not by itself improve light transmission.  In that regard, given equal quality coatings, there is no substitute for a larger objective.  An ED 65mm scope can in some cases provide a sharper, more defined image than an 85mm non ED scope, depending on the 2 scopes being compared.  Assuming both are high quality scopes, the difference will not be that great.  If you are willing to live with a smaller objective for more "handiness," a 65mm ED scope will give you reasonable light transmission, and the image quality provided by the ED glass will for the most part make up for the difference in objective size.
 
So, the choice basically boils down to whether you value slightly better low light performance, or easier portability.  You can't have both.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 14:36
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This is an interesting topic with no simple answer.

I think I will write up a little note on it and post it in a different thread.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 14:40
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Thanks to both of you for the thoughtful and informative replies. The conundrum over low light performance vs. portability is a difficult one. I have a pair of 8x24(or 25) Leupold binos that I got for $49, which under bright light are almost as effective as the glass in my Swaro rangefinder (8x30). However, even as a monocular, the Swaro is less fatiguing because of the better quality glass. Neither is great for low-light usage.

Low light performance is a good issue to consider, since there can be significant opportunities early or late in the day when hunting. Personally, I've found that animals are less wary coming off their nocturnal feeding than they are later in the day. So having a good pair of easily accessible 8x42/3 binos is enough since I can get close enough (400 yards or less) to establish if that is the animal I want to shoot. I'm interested in a better spotting scope but mainly for target shooting out to 600 yards. Through my current low-budget Bushnell 18-36x50, I can see and interpret .30 cal bullet holes out to 300. So it sounds like a larger objective scope maybe made less expensive by lesser glass would do fine. But the 60-66mm range would be more portable and I can't imagine how a 20-60X 60mm Kowa couldn't significantly outperform the Bushnell. As it stands, I have to set the spotting scope up half way between and walk out to it to check my results. That is time consuming, although it allows the barrel to cool between groups and I usually take the .22 along to plink while I'm walking there and back (this is not at an established range).
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 14:47
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I would be very surprised if the Kowa you mentioned didn't outperform the small Bushnell scope.  I'm not skilled enough to be shooting at things 600 yards away so; I've never tried to see bullet holes on paper that far away. 

Edited by lucznik - July/31/2009 at 14:47
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 17:46
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Originally posted by lucznik lucznik wrote:

I would be very surprised if the Kowa you mentioned didn't outperform the small Bushnell scope.  I'm not skilled enough to be shooting at things 600 yards away so; I've never tried to see bullet holes on paper that far away. 


I know from shooting out to 600 yards (and occasionally beyond) that I am not skilled enough nor do I have the right rifle to target large game at that distance. It does help build confidence for shorter-range shots though. Now 100 yards is like nothing and 300-400 yards is feasible if the winds aren't too tricky. Smile
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 20:34
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I have watched the whole "ED" phenomenon for some years now, and been able to compare many optics both before and after ED (or whatever kind of glass) was added to the mix. In general I have been underwhelmed. There have been some slight differences seen in some optics, but none that were so earth-shaking as to make glassing any more productive with the so-called ED version at least 99% (and maybe 99.9%) of the time.

In general new engineering of the rest of the system is probably at least as important. But once one manufacturer started using ED glass (or whatever it is called by whomever) then every other manufacturer had to follow. Otherwise they'd be left in the advertising dust.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/31/2009 at 23:50
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I'm eagerly awaiting Koshkin's ED thread. Meanwhile, the more I've researched spotting scopes the less it seems a new one will be of much value to me, especially compared to all the other hunting-related things you could spend money on that would probably be of more use. I think I'd rather have a great pair of binos or get more reloading supplies and just get in more range time.

This article in particular - http://www.6mmbr.com/spotterreview.html - puts the kibosh on one of my goals: a spotter capable of resolving .30 cal holes out to 600. If mirage is going to be a problem for the uber-alpha scopes then it is going to be a problem for anything within my budget. Just two days ago, while shooting across an old clearcut at 6100' on a 75 degree day I detected slight mirage through my scope on 10X. I can only imagine what it's like viewing through 60X magnification on a 95 deg. day.

That said, if John is right about the "ED" hype, then here's a scope I think could be a good deal - the ugly-a** camo version of the Kowa TSN-602: http://swfa.com/Kowa-60mm-Spotter-P8062.aspx. At $379.95 for the body, it's $60 less than the plain model and for just under $750 you could have that with the 20-60X eyepiece. But I'll just keep walking and plinking my way back and forth for those long-range shots and figure out which binos will make all my hunting dreams come true.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/01/2009 at 08:50
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Originally posted by John Barsness John Barsness wrote:

I have watched the whole "ED" phenomenon for some years now, and been able to compare many optics both before and after ED (or whatever kind of glass) was added to the mix. In general I have been underwhelmed. There have been some slight differences seen in some optics, but none that were so earth-shaking as to make glassing any more productive with the so-called ED version at least 99% (and maybe 99.9%) of the time.

In general new engineering of the rest of the system is probably at least as important. But once one manufacturer started using ED glass (or whatever it is called by whomever) then every other manufacturer had to follow. Otherwise they'd be left in the advertising dust.



Thanks for the exellent post.  I've often wondered this very thing.  How much is hype just to increase sales, and how much practical advantage would it give me in actual hunting conditions?  I think this post by JB sheds some very important light for me. Thanks to all.
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