SWFA's 2009 Scope Rating Scale

[MCMXI]

Well first of all the 6500 glass in is not multicoated it is fully multicoated. Secondly why does leupold saying the mk4 lenses are index matched mean they are better optically than the Bushnell 4200/6500 glass? This is not the first time that someone has claimed the Bushnell elite 4200/6500 glass is better than VX-III glass so it should not be too much of a suprise.

First off, INDEX MATCHED is superior to FULLY MULTICOATED ... even Leupold acknowledges that.

The non "tactical" 6500 have 78 adjustment moa while the mk4's have 100 (I believe)

According to Bushnell's own web site, the 6500 series (4.5 to 30X) and their new "tactical" series has 50 inches of vertical adjustment at 100 yards ... why they specify 100 yards I don't know ... perhaps it's to indicate that their adjustments are IPHY. Either way, that equates to 47.7 MOA at 100 yards. Mark 4 8.5 - 25X scopes have 75 MOA adjustment at any distance.

 

[Zak Smith]

I am personally more interested in objective tests vs. marketing materials...

 

[lipadj46]

First off, INDEX MATCHED is superior to FULLY MULTICOATED ... even Leupold agrees with that.

Are you sure you know the difference between what index matching is and what fully multicoated is? Because the mk4's have fully muticoated optics too as do all high end scopes. Index matching really does not mean much except they are going to be clearer than other leupold glass with the same coating that are not index matched.

According to Bushnell's own web site, the 6500 series (4.5 to 30X) and their new "tactical" series has 50 inches of vertical adjustment at 100 yards ... why they specify 100 yards I don't know

Because 1 moa = 1 inch at 100 yards. Yes their tactical scopes have less adjustment than their non target models but then I am not sure who is buying a 6500 tactical. They are really hunting scopes and 78 MOA of adjustment is great for a hunting scope.

 

[Zak Smith]

[Because 1 moa = 1 inch at 100 yards.

Not exactly.

Of all people who should be precise about 1 MOA vs. 1 IPHY, it should be scope manufacturers! One might be surprised how often they screw that up.

Doesn't matter? It does when you dial 29 MOA for 1000 yards instead of 27.75...

 

[MCMXI]

I am personally more interested in objective tests vs. marketing materials...

That was my earlier point ...why aren't there scientific tests of the "clarity" and "brightness" of the scopes in question. They're always going to be subjective at best.

And why does index matching mean that the mk4 glass is better? How do you know that the 4200 and 6500 glass is not index matched?

Read up on index matching of lenses and you'll soon discover that it's THE WAY to go to achieve the least amount of refraction, dispersion, attenuation and absorption of light all of which are detrimental to scope performance.

 

[MCMXI]

Are you sure you know the difference between what index matching is and what fully multicoated is? Because the mk4's have fully muticoated optics too as do all high end scopes. Index matching really does not mean much except they are going to be clearer than other leupold glass with the same coating that are not index matched.

Are you kidding me? Of course the Mark 4s are fully multicoated, but they're ALSO index matched which not only means that they're brighter and clearer than other Leupold non-index matched scopes (I know since I have them), but they're also clearer and brighter than non-index matched scopes from OTHER manufacturers.

If Bushnell Elite scopes had index matched lenses, believe me, they'd mention it on their web site.

 

[benzy2]

I don't mean this as a ding against Leupold, just a comment. Would index matched coke bottle glass be better than the 4200/6500 glass? As I understand it all index matching does is put a different, supposedly optimized, coating on each lens instead of the same coating on all lenses. As far as I had seen Bushnell states their fully multicoated lenses have all surfaces having multiple layers of coating. They never say that every surface gets the same amount of layers. Personally I had thought all companies top lines that were fully multicoated were done the way the index matching is done and that the term index matching was just a marketing device. This states nothing of the quality of the glass as well. I'm not picking sides as to if the Mark 4 should be higher or not. That wasn't my point. Out of curiosity does anyone have the light transmission numbers for the mark 4 and for the 4200/6500 line? I bet they are right in line with each other from what I remember.

EDIT: And no if Bushnell "index matched" their scopes they wouldn't have it on their site because it is a registered phrase that Leupold owns.

 

[lipadj46]

Read up on index matching of lenses and you'll soon discover that it's THE WAY to go to achieve the least amount of refraction, dispersion, attenuation and absorption of light all of which are detrimental to scope performance.

I guess we will have to agree to disagree on what Leupold calls it's proprietary brand of optical coating compared to other manufacturer's proprietary lens coatings (what is Leupy calling the VX-3 and VX-7 coatings these days?). I know some do not like to think that a lowly Bushnell may have better optical performance than their mk4 but unfortunately many think so. I know that many rabidly disagree though.

 

[MCMXI]

From Nightforce's web site ...

"Every lens in a Nightforce scope is matched and aligned by hand perfectly to its partners. This technique, called optical indexing, yields the highest possible optical performance. Because it takes time and considerable expertise, many manufacturers don't bother. We've done it this way since the beginning."

Optical indexing of lenses is the same as index matching of lenses.

"All air-to-glass surfaces receive our proprietary broadband multi-coating; applied to tolerances of 1/4 wave deposition or .000005 inches, exceeding the toughest Mil-Spec abrasion test. You will see the difference in low-light situations.

A scope’s objective lens determines resolution, light transmission and exit pupil size. To maximize these attributes, every Nightforce objective lens assembly utilizes a multi-element design like those found in the highest quality telescopes. Our lens system focuses light rays more precisely for exceptional image clarity and color accuracy.

Nightforce tubes are machined from solid bar stock 6061-T6 aircraft-grade aluminum alloy, not extruded or formed like those found on lesser scopes. They are two to three times thicker than other riflescopes. This means less overall stress, greater thermal stability, a consistent zero and a virtually impervious shield for the precision optics within."

Both Nightforce and Leupold use proprietary multi-coatings AND index match the lenses. In addition, both machine their scope tubes from billet aluminum. Bushnell touts the fact that their scopes are "hammer forged" which Nightforce refers to as a technique used in "lessor scopes".

 

[lipadj46]

Are you kidding me? Of course the Mark 4s are fully multicoated, but they're ALSO index matched which not only means that they're brighter and clearer than other Leupold non-index matched scopes (I know since I have them), but they're also clearer and brighter than non-index matched scopes from OTHER manufacturers.

If Bushnell Elite scopes had index matched lenses, believe me, they'd mention it on their web site.

Leupold makes some tasty kool-aid don't they

I believe you are talking about 2 different processes now. Optical indexing via measurements and matching lenses with other lenses is different than the index matching via coatings. You better believe all high end optic companies have proprietary coatings Leupold just happens to like claiming their multicoatings are special and name them something neat for folks to suckle up.

In addition, both machine their scope tubes from billet aluminum. Bushnell touts the fact that their scopes are "hammer forged" which Nightforce refers to as a technique used in "lessor scopes".

Well it is a more expensive process I will give you that.

 

[benzy2]

No index matching as Leupold states is putting different coatings on the lenses. That is it. Index matching is nothing more than putting different coatings on different lenses or lens surfaces which they claim makes for a brighter and higher resolution picture. What does NF mean by matched? They are even more vague than Leupold. Not to say they aren't better but to just say I match and align everything doesn't mean squat. Again I will ask if you are so big that index matching makes things better do you have resolution chart results and light transmission results from even one Leupold scope to another to state if there is potentially any truth to these trade mark terms or are you just going based on the marketing that a cool term must be good?

 

[MCMXI]

Leupold makes some tasty kool-aid don't they

Again I will ask if you are so big that index matching makes things better do you have resolution chart results and light transmission results from even one Leupold scope to another to state if there is potentially any truth to these trade mark terms or are you just going based on the marketing that a cool term must be good?

So why is it that high-end astronomical telescopes rely heavily on index matching of lenses? All you have to do is read about index matching on astronomy related sights where noise is a BIG problem to realize the benefits of index matching.

Multi-coating all of the lenses and then stacking them up in the scope is not the same as taking the time to match the lenses either by selecting specific refractive indices or coating lenses to obtain specific refractive indices. These matching systems are proprietary and there's no doubt that Nightforce, Schmidt & Bender, US Optics, Leupold etc do it in slightly different ways, but their objectives are the same ...

lipadj46, what scopes do you currently own? How about scopes that you've owned in the past. I've made no secret of the fact that I have a number of Mark 4 scopes and I've owned quite few low-end scopes over the years.

This might help to shed some light on the benefit of index matching.

"When light is focussed by passing it through a lens made from ordinary glass, such as crown glass, each wavelength of light bends a different amount. This is the reason, we are able to see light separated into its spectrum when it passes through a glass prism. This different bending leads to a problem, because each wavelength focusses at a different point. The result is a focal zone rather than a focal point. When a bright object is viewed through such a lens, it is blurry and has a fringe of false colour. Technically, this is referred to as chromatic aberration. Reflectors don't suffer from this effect because their light rays don't pass through any glass. A second problem, called spherical aberration, occurs when optical surfaces of lenses or mirrors are not properly figured or shaped. As with chromatic aberration, the focal point becomes a focal zone ...

... a second approach is to add another matching lens of a glass having a different refractive index. For example, when positive, low-index, BK7 crown glass is matched with negative, high-index, F2 flint glass, the light rays are bent again so that all wavelengths focus near the same point. The result is called an achromatic refractor and the matched lenses may either be cemented together, or air-spaced by mounting them in a cell which holds them in their correct positions. The two-element lenses used in today's achromats greatly reduce the chromatic aberration. For example, it has been brought to low levels in Sky-Watcher 1201EQ5 and 15012EQ6.

In the ongoing search for the perfect telescope, lens makers produced other lens element combinations and special types of glass, in order to remove all of the false colour. These developments have resulted in semi-apochromatic (almost without colour) and apochromatic (corrected in three colours) refractors but these are very expensive compared to achromatic refractors."

 

[lipadj46]

I know what it means, I took an optics class at Columbia University back when I was in engineering school there.

This is what Leupold is talking about when they say index matched:

Index Matched Lens System A Leupold® exclusive, this system has nearly perfected Leupold’s already impeccable light management. Leupold engineers specify different coating materials for each lens surface in the riflescope, based on the lens’ index of refraction, placement and function, layering each coating to eliminate reflections and maximize light transmission. The result is unparalleled brightness and extremely sharp resolution across the entire visual field.

Which sounds very different from this:

Every lens in a Nightforce scope is matched and aligned by hand perfectly to its partners. This technique, called optical indexing, yields the highest possible optical performance. Because it takes time and considerable expertise, many manufacturers don't bother. We've done it this way since the beginning

Like I said Leupold not only has very skilled engineers but also very savvy marketting gurus.

Forgot to add the last Leupold scope I owned was a mk4 10x back in 2002 on a Serbu .50 BMG, also had a Super Sniper at the time in 10x which was also a good scope for the money also had a couple varix-III's. I sold most of my stuff to pay off my ex wife and because I was living in NYC at the time and traveling a lot. Now I own a 4200 on a M1A and a Monarch on a ruger hawkeye plus a bunch of other random scopes like prostaffs and weaver classics on a 336 and shotguns. If I do buy another tactical scope it will probably be an IOR.

 

[MCMXI]

How do you think Nightforce MATCHES their lenses? The SAME way as all the other high-end manufactures that MATCH their lenses ... by varying the type, number, order, and thickness of their coatings. That's what INDEX MATCHING IS ... controlling (matching) the index of refraction for lenses so that they work together to have a minimal effect on the light that passes through them. So in fact, those two methods with different names refer to the same process with the same objectives. The added time and effort are reflected in the cost and quality of the final product!!

As for the terms fully-multicoated or multicoated lenses, these ARE NOT matched by definition alone.

The pity here is that Bushnell probably makes a very decent scope at an affordable price for many people with enough features and sufficient performance for most shooters. Sadly, that's not enough for those people. They have to convince themselves (and others) that their Bushnell is every bit as good, or better than a Mark 4 and anyone with a Mark 4 is a sucker or a victim of Leupold's "savvy marketting gurus". However, for all the hype, no military unit uses them, they're not battle-proven, long-range competitive shooters don't use them, they're not on the podium at long-range events, heck, they're not even featured, so why not be content with the Bushnell for what it is and leave it at that?

 

[benzy2]

I guess I just don't get how a company comes up with their coating formula if it wasn't using index matching. How else would you develop a coating than the way described? Did they just randomly make up coatings before until one looked decent and stuck with that? I'm serious what other way would you develop a coating system? I don't have as much knowledge here so I'm asking. Wouldn't you design different coatings and number of layers for each lens to make the image as bright and with the most resolution possible? I thought that was the goal of fully multicoating? I guess I just don't see what other way you design coatings.

 

[MCMXI]

From Schmidt & Bender ... the last two paragraphs are particularly interesting.

"It is impossible for any scope to "gather" light. It can only transmit existing light. And, regardless of advertising claims you may have heard, there is no riflescope made that can transmit 100% of available light.

As light enters the objective end of the scope, before it reaches your eye it passes through several lenses. Each lens absorbs a small quantity of light. Residual reflection from the individual lenses will also prevent a certain amount of light from passing through the scope. In addition, undesired reflections within the metal tube can hinder the quality of the viewed image and the transmission of light.

Each lens has two surfaces. Thus, the total number of lenses within a scope (a variable-power scope can have between seven and ten) is multiplied by two, then multiplied by 0.25% to determine the amount of light lost in the transmission. Simple multiplication is not accurate, however, as each succeeding lens progressively reduces the total amount of transmitted light. It is a favorite technique of some scope manufacturers to claim light transmission values of nearly 100%. Of course, they're measuring the first objective lens only, conveniently forgetting about the other eight or nine!

Any higher transmission levels are physically impossible to achieve with current technology, and claims to the contrary are to be discounted. What does light transmission mean in practical terms? An average scope may transmit 85% or so, and inferior scopes substantially less. The human eye can distinguish transmission differences of 3% or more. Consequently, there is a very real difference in what you can see through a superior scope versus run-of-the-mill optics.

The very best rifle scopes human beings can create will transmit to your eye—under perfect conditions—a maximum of 94.5% to 95% of available light. There are but a handful of scope companies remaining that produce optics approaching these levels, Schmidt & Bender being one of them.

Under hunting conditions, when you might be trying to distinguish a target at absolute last light, these differences can be critical. It can determine whether you bag your game or whether you have long since called it a day.

The quality of the coatings utilized on rifle scope lenses (and the skill of the company applying them) are one of the most critical factors in determining the light transmission properties and low light performance of a scope. Good modern coatings are known as "broad band" coatings because they transmit a broad range of the visible light spectrum (i.e., 350 to 780 nm) with a high degree of efficiency. The weighting and mixture of different values of visible light are calculated as "day value" and "twilight value."

Lens coatings are carefully guarded secrets, formulated by skilled physicists. We calculate the makeup of our coatings in direct relation to the physical composition of the glass to which it is applied, since glass can react in differing ways to the same coating. Our coatings are weighted in favor of certain nanometer (color) values, giving preference to certain wave lengths which are most beneficial to the hunter under actual field conditions (see "what is light").

A simple test that will help you determine the quality of a scope's lens coatings is to look into the front objective lens as you would with a mirror. You should not see yourself. If you do see your reflection, it indicates that light is being reflected back instead of passing through the scope. "

Since according to Schmidt & Bender, average scopes transmit 85% of light and excellent scopes transmit up to "a maximum of 94.5% to 95% of available light", I would think that this would be a relatively easy scope test to set up to give OBJECTIVE, SCIENTIFIC data regarding clarity and transmission at least. The representation of colors could be established with a standard color chart at fixed distances under controlled lighting conditions.

Zak, sounds like this could be your next article.

 

[Zak Smith]

I could do that if I got my hands on some optical equipment. As it stands, I'm stuck with a Snellen chart @ 100 yards and several sets of eyes. (I do have a last-2-year LR scope roundup in the works now.) However, this is somewhat irrelevant for the kinds of scopes I'm interested in. The ones that have the features needed for practical LR shooting usually have pretty good optical quality anyway.

Although it's a pleasure to use super clear glass and I can notice a difference switching between SB/USO and other scopes, there are other things that are honestly more important to making hits, like: reliability, zero-retention, design to prevent human error, consistent tracking, etc.

 

[MCMXI]

Although it's a pleasure to use super clear glass and I can notice a difference switching between SB/USO and other scopes ...

Zak, Schmidt & Bender makes the point that ...

"Our coatings are weighted in favor of certain nanometer (color) values, giving preference to certain wave lengths which are most beneficial to the hunter under actual field conditions (see "what is light")."

... so how much is our perception of scope glass quality a function of how we react to the "color scheme" selected by each scope manufacturer?

 

[Zak Smith]

I couldn't say but it's also apparent on a Snellen chart (eye chart) which is black and white.

 

[benzy2]

That's where actual data would be important because Bushnell claims their 4200 line transmits 95% of light at 550 nm. I thought they claimed the same for the 6500 line and 92% for the 3200 line but I am having troubles finding that info right now. I knew Bushnell claimed 95% light transmission and I hadn't heard many other companies claim greater than that. I don't know if Bushnell's claims are true or not. My point was from the beginning was that it is a big claim to say the "index matching" results in a brighter scope than those spec'ed at 95%, which by manufacturer claims the Bushnell is. I would trust Bushnell's marketing department as little as I trust Leupold's though I will say giving numbers instead of a system certainly is a claim that can be tested and either accepted or refuted to be true.

 

[lipadj46]

I would trust Bushnell's marketing department as little as I trust Leupold's though I will say giving numbers instead of a system certainly is a claim that can be tested and either accepted or refuted to be true.

Also Bushnell tells you at what wavelength of light that there is 95% transmission (~550nm As I recall which is in the visible spectrum obviously) which gives it credibility that it actually is a real number spit out of an instrument. That is obviously the the max transmission and it is less at other wavelengths. I do not know what the average transmission is as I also do not know what Leupold's peak transmission is and at what wavelength becasue they do not report it on their website nor the average.

"Our coatings are weighted in favor of certain nanometer (color) values, giving preference to certain wave lengths which are most beneficial to the hunter under actual field conditions (see "what is light")."

That is exactly what the 95% at ~550nm (visible spectrum) from Bushnell means. It will be the same for every scope. They will transmit some wavelengths better than others. Hopefully the ones they transmit the best are the wavelengths you see the best. And also some companies may report 99% transmission but it is in the UV spectrum that we cannot see at all.

I guess I just don't get how a company comes up with their coating formula if it wasn't using index matching. How else would you develop a coating than the way described?

They do and that is my point (and your I guess)

 

[kyle1974]

I'm guessing that the index matching refers to matching the specific refractive index of a particular solid. Air, water, glass, minerals.... they all have a refractive index. I would guess that by matching the refractive index values exactly, the result is a sharper image. I don't think this is done with coatings, but instead by actually matching different pieces of glass to another.

 

[TRGRHPY]

If this is supposed to have a slant towards hunting, why does durability carry such low weight score?

 

[MCMXI]

I'm guessing that the index matching refers to matching the specific refractive index of a particular solid. Air, water, glass, minerals.... they all have a refractive index. I would guess that by matching the refractive index values exactly, the result is a sharper image. I don't think this is done with coatings, but instead by actually matching different pieces of glass to another.

In the case of optics, every decent scope manufacturer uses some form of multicoat system. Once all the lenses are coated, they will all have varying refractive indices due to variations in glass, coating thicknesses, small (or large) variations in coating chemistry etc .... can we at least all agree on that? If you take the time to measure the refractive index of each COATED lens, and then assemble the lenses in SETS where the refractive indices are ideally MATCHED, then that is called INDEX MATCHING. Not all scope manufactures do that.

If this is supposed to have a slant towards hunting, why does durability carry such low weight score?

... or military application where scope durability can mean the difference between life and death!! That list is BS as I've already mentioned.

I've been reading about the Bushnell Elite 6500 and reports from folks that have bought them claim ONLY 44" of vertical adjustment which is even less than the 50" claimed by Bushnell. Now convert to MOA (divide by 1.047) and it's even less ... about +/- 21 MOA!! At around $800 to $900 for the Elite 6500 that's just not good enough. If you must have a Bushnell, surely the tactical line would be better if you can figure out Bushnell's ridiculous web site with conflicting data at every turn.

http://www.bushnell.com/general/riflescopes_elite6500_65-2164t.cfm

http://www.bushnell.com/general/riflescopes_tactical_65-2164t.cfm

So which is it ... a 44mm or 50mm objective. Why report the 6500 to have 50" of adjustment when it only has 44"? Combine that with Bushnell's obvious errors with their use of MOA for IPHY gives me little confidence in anything they report on their web site.

lipadj46, so what's the difference between the 4500 line and the 6500 line in terms of optical performance, technology etc?

 

[benzy2]

I called Leupold today asking about their index matching. I hung up even more confused than before. I asked about index matching and was told that the coatings were specific to a lens type and material. Then I was told they were coated based on the lens index of refraction, though it was specified if it was for individual lenses or not. After that I was told the coatings may slightly vary from scope to scope, which I don't know if they meant it was their tolerance or if it was due to each lens being individually coated to its own slightly different spec. I think I will email them to hopefully give them a bit of time to prepare for the question and give me a straight answer.

As for the Bushnell, yep they do have limited turret adjustments. Always have. It is why I skipped them on my rimfire range rifles. I need too much adjustment for my shooting than to go with one. To the average hunter though it isn't going to mean much as a lot of guys set it and forget it. The listing is geared towards hunters, not tactical shooters or the range warrior. If you want to make a tactical shooter scope classification go for it. Being upset because a tactical scope didn't rate well as an average hunter's scope is what it is. There are certainly things the Mark 4 does better than the 4200/6500 line, but most of this is really only beneficial to the tactical shooter which this rating system isn't set up for. I believe the extended magnification is a big part of why the 6500 line did so well. For the average hunter I would have to believe that is far more important than being able to dial in 100 MOA of vertical. As for the glass in the 6500 I believe it is 4200 glass with the same coatings. Actually I believe that all of the glass from the 3200, 4200, and 6500 is the same, just that the 3200 isn't fully multicoated while the 4200/6500 is, but I haven't seen that verified so take that for what it's worth.