Rifle Scopes Why isn't glass objectively measured?

[dbooksta]

I'm so sick of reading subjective evaluations of glass quality in riflescopes. Why isn't this something that is objectively measured? AFAIK the only optical characteristics of a scope that matter are:

1. Resolving power
2. Light transmission across the visible spectrum
3. Distortion

We expect any decent company to list reticle adjustment range, exit pupil and eye relief. Why not these other parameters?

 

[ORD]

Re: Why isn't glass objectively measured?

Ah...if only life were so simple! ;-)

 

[glock24]

Re: Why isn't glass objectively measured?

It makes it hard for the manufacturer to amaze and mystify the paying customer when variable data is involved.

 

[bigwheeler]

Re: Why isn't glass objectively measured?

Digitals coming, don't worry.

 

[lightwind]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">I'm so sick of reading subjective evaluations of glass quality in riflescopes. Why isn't this something that is objectively measured? AFAIK the only optical characteristics of a scope that matter are:

1. Resolving power
2. Light transmission across the visible spectrum
3. Distortion

We expect any decent company to list reticle adjustment range, exit pupil and eye relief. Why not these other parameters?
</div></div>

Great question and I have wondered the same thing. However, after looking into it I don't see any simple solution. For instance:

1) Resolving power of what? Look up visual acuity or resolving power and you will find it is tied to the eye. It would also be subject to sample errors as well as consistency in the manufacturing process. The simple lens laws don't take into consideration all of the manufacturing issues. So, do I compare the lens law resolving power of an ideal lens, a lens made in China, or a lens made in the US? I can have the same theoretical resolving power for two scopes with one made by US Optics and one made by BSA. Does an equivalent lens law tell me they are the same?

2) Light transmission across the visible spectrum? Again manufacturing of coatings. How consistent will it be? Also, the eye is not of the same sensitivity to each wavelength. How do you take into consideration the proprietary coatings from each company?

3) Distortion? What kind of distortion? How will you measure it? Will it be from one of the manufacturers best lenses or from your scope? Will I expect consistency from a scope that costs $150 versus one that costs $2000? Look up distortion and you will find multiple kinds.

Don't get me wrong. I share your frustration. However, when it comes down to the bottom line you have to look through the scope.

 

[GUNNER75]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"><span style="font-weight: bold">Don't get me wrong. I share your frustration. However, when it comes down to the bottom line you have to look through the scope.</span></div></div>

 

[dcjs]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">1. Resolving power</div></div>Resolution is almost worthless without contrast. You can measure contrast at different resolutions as MTF curves over the image height, but you also have to be able to read those curves. There is a very good PDF guide about how to read MTF charts published by the Zeiss photographic lens division. It is 33 pages long.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">2. Light transmission across the visible spectrum</div></div>This is the only thing from the list that would be practical to measure and publish.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">3. Distortion</div></div>Most people don't even have a clue about the definition of "distortion" of an optical system.

There are hardly any simple measurements that you can read as "bigger/smaller number is better", and I'm afraid that those who ask the loudest for numbers would be those who wouldn't know what to do with them if they had them.

For example, if someone started publishing "maximum resolution" figures and people started buying the scopes that maxed out those tests, scope companies would start optimising their scopes for this figure, and since optics design is a big pile of multilaterally connected tradeoffs, the result would be scopes with high central resolution, crappy edges and low contast that you couldn't see shit with in many practical situations.

It's somewhat like asking the Guide Michelin to get rid of their testers and start using "scientific numbers" to rank restaurants.

 

[dbooksta]

Re: Why isn't glass objectively measured?

Of course I'm thinking of sample measures, not ideal or theoretical measures.

For example, an ideal rifle with ideal ammo shoots to the same point-of-impact every time. In reality there are a lot of variables, but we still have some manufacturers sending test targets with their guns, and many others who guarantee 5-10 shots within 1/2-1MOA with factory ammo. Compared to test-firing a gun a scope is easy, since for every single production piece you can plop it in a test jig and record:

1. A 2-D chart of light transmission by frequency. Useful summary number: min transmission within visible frequencies.
2. A 2-D distortion chart. Reasonably useful summary number: Max % sum-squared distortion.
3. A 3-D aberration chart. Reasonably useful summary numbers: Peak and sum-squared aberration.
4. MTF curves. Reasonably useful summary number: sum area under curve.

You don't need a profound understanding of those charts or numbers to determine:

A. Whether your scope meets the performance/quality specs advertised by the manufacturer
B. Whether one scope is of notably higher quality than another

 

[dcjs]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">3. A 3-D aberration chart. Reasonably useful summary numbers: Peak and sum-squared aberration.</div></div>I had my doubts before, but now I'm reasonably sure that you have no idea whatseover what you're talking about. That, or you are a genius and have somehow figured out how to display the various types of aberrations of an optical system in one meaningful visualization.

 

[rezmedic54]

Re: Why isn't glass objectively measured?

What did he Say??????????????????????

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: David S.</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">3. A 3-D aberration chart. Reasonably useful summary numbers: Peak and sum-squared aberration.</div></div>I had my doubts before, but now I'm reasonably sure that you have no idea whatseover what you're talking about. That, or you are a genius and have somehow figured out how to display the various types of aberrations of an optical system in one meaningful visualization.
</div></div>

Wow, no quarter here! I didn't mean to suggest I have a magic diagram that summarizes all optical defects and aberration effects in an optical system. I was just thinking some sort of profilometry on each lens or the system might be useful. If that sounds like a stretch then never mind; we'd all be better off than we are now with even one of the other 3 figures widely reported in a standardized form within the industry.

 

[lightwind]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">I'm so sick of reading subjective evaluations of glass quality in riflescopes. Why isn't this something that is objectively measured? AFAIK the only optical characteristics of a scope that matter are:

1. Resolving power
2. Light transmission across the visible spectrum
3. Distortion

We expect any decent company to list reticle adjustment range, exit pupil and eye relief. Why not these other parameters?
</div></div>

I hope you don't think we are just all piling on because most of us would like to have simple objective measures. However, read this information on optical resolution:

http://en.wikipedia.org/wiki/Optical_resolution

That will give you an idea of the complexity of just resolution. No scope is ever difraction limited. Instead, the limits are based on the manufacturing process. You can bet that every good manufacturer keeps those processes proprietary. That is the reason you get subjective responses from experts who use them. They will talk about contrast, resolution, clarity, "popping out" and other subjective responses. That is because every scope you look though has been through a slightly different process. We would all like something more objective, but the response of experts who look through the scopes is about as objective as you can get. That is one of the reasons you seem flame responses when someone's pet scope gets bad-mouthed. Not because they have something objecive to say, but rather they always have something subjective to say. So, should we start the traditional flame wars over manufacturers?

 

[bth87]

Re: Why isn't glass objectively measured?

JMHO, but does it really matter if a company can provide objective optical information for their scopes? In my mind all of the top teir manufactures put superb glass in their scopes and for me it is far more important that the optic be robust and mechanically reliable, who gives a shit if S&B or Premier or Henny has the best glass because they are all awesome. At the end of the day glass dosent hit the target, the mechanics of the optical system and a competent shooter does.

 

[SPDSNYPR]

Re: Why isn't glass objectively measured?

I think I have understood fewer things said in this thread than any other I have ever seen posted in the English language.

 

[bhoges]

Re: Why isn't glass objectively measured?

Why doesn't somebody who is optics savy come out with a standard to test scopes by? Thats what bothers me about magazines and writers nobody is willing to bash a company on their products for fear of losing an advertiser. Its conmplicated but their are ways to compare scopes that would help show differences.

 

[Killer Spade 13]

Re: Why isn't glass objectively measured?

Because everybody's eyes are different . . .

 

[XTR]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: David S.</div><div class="ubbcode-body">... wouldn't know what to do with them if they had them.

For example, if someone started publishing "maximum resolution" figures and people started buying the scopes that maxed out those tests, scope companies would start optimising their scopes for this figure, and since optics design is a big pile of multilaterally connected tradeoffs, the result would be scopes with high central resolution, crappy edges and low contast that you couldn't see shit with in many practical situations.
</div></div>

^THIS^

Great point in this post.

Take one look at the motorcycle business, peak HP sells sport bikes, but since that peak is achieved in the last 1000 RPM before the redline 99% of the squids who buy a 'busa (which won't turn much better than a Harley) or a Gixxer or any other sport bike for that matter have not the skill nor the locations to ride a bike that way. In the mean time something with a good wide midrange torque band that in real world riding is far and a way more useful will be ignored.

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bth87</div><div class="ubbcode-body">JMHO, but does it really matter if a company can provide objective optical information for their scopes? In my mind all of the top teir manufactures put superb glass in their scopes and for me it is far more important that the optic be robust and mechanically reliable, who gives a shit if S&B or Premier or Henny has the best glass because they are all awesome. At the end of the day glass dosent hit the target, the mechanics of the optical system and a competent shooter does. </div></div>

Right, this wouldn't be as interesting for comparisons within the top tier manufacturers, but rather for making informed trade-offs between the first-through-fourth tiers. For example, what do you get, <span style="font-style: italic">optically</span>, going from a $700 Nikon to an $900 Sightron to $1200 Vortex to a $1500 IOR to a $1700 Leupold to a $2200 Nightforce to a $3300 S&B?

If every scope above $700 has 96% light transmission across the spectrum that would be interesting.

If Sightron has edge-to-edge distortion comparable to Hensoldt that would be illuminating.

If Burris MTF curves are as high and level as S&B's, then wow.

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body">Take one look at the motorcycle business, peak HP sells sport bikes, but since that peak is achieved in the last 1000 RPM before the redline 99% of the squids who buy a 'busa (which won't turn much better than a Harley) or a Gixxer or any other sport bike for that matter have not the skill nor the locations to ride a bike that way. In the mean time something with a good wide midrange torque band that in real world riding is far and a way more useful will be ignored. </div></div>

Well at least they all list peak HP! Of course for "power" you care more about the torque curve, but (1) you can predict that pretty well based on engine type and size, and (2) some manufacturers actually advertise their torque curves, and anybody who pays as much attention to their bikes as we do to our shooting equipment will be looking at the torque curves.

For scopes pretty much all we get are assurances that "lenses are fully multi-coated for maximum light transmission." Some manufacturers will throw out an actual light transmission figure, but presumably that's at their peak frequency, not the full spectrum transmission curve. It's not expensive for them to sample and publish the full curve, and I'd love to see both level and smoothness of transmission curves. Instead of subjective evaluations like, "I think scope A has better low-light performance than scope B," we could just look at the curves and say, "Well, duh, that scope's transmission below 450nm is only 85%."

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brian</div><div class="ubbcode-body">Why doesn't somebody who is optics savy come out with a standard to test scopes by? Thats what bothers me about magazines and writers nobody is willing to bash a company on their products for fear of losing an advertiser. Its conmplicated but their are ways to compare scopes that would help show differences. </div></div>

Exactly. And like you said, this probably won't come from the writers who can never say anything negative or do an objective side-by-side that would make one of their advertisers look bad.

I'm just surprised none of the manufacturers -- especially the ones like IOR who probably are top-tier but don't have the franchise to charge a premium -- don't step up to the plate to differentiate themselves.

If Nikon or Zeiss threw down the gauntlet and published MTF curves and distortion charts on their scopes -- that would be like the first rifle maker who guaranteed his gun would shoot 1/2MOA and included a certified test target to "prove" it.

 

[noname]

Re: Why isn't glass objectively measured?

if your really interested -- go to the web on MTF (modular transfer functions) under a contributer first name norman (can't) remeber last. download his matlab program, get a digital camera (a really good one)take off the lenses build a jig take picture thru scope save in TIFF or readable file, run thru matlab for fourier and wavelet transforms and mtf. Get a model of every scope produced run data. Post data on SH.
Then get a post from someone who will tell you that due to the divisive gain built into the HVS (human visual system)your data is meaningless.

 

[Lowlight]

Re: Why isn't glass objectively measured?

The glass quality is a distant secondary, in consideration.

Accuracy & tracking is what matters the most. Especially in the mid range optics, because let's face it, they all look good enough when you take them out of the box. The test of glass quality usually isn't . It's a test of coating quality and any real test of that, glass and coatings are measured in the long term not the short. How well the glass and coatings hold up to exposure and use, or does it break down and cloud? Out the box, complete waste of time.

It's why a company like IOR as noted above isn't top tier, while they have very good glass overall their internals are not up to the task. While they may work well for people with limited range and experience because they are a good price and give the owner a wow factor looking through it, when te time comes to actually use it, well it seems to always be 50/50.

People who talk glass are just looking to impress their friends while staring through the scope out their living room picture window. I'd rather it be mechanically sound.

 

[valise]

Re: Why isn't glass objectively measured?

The OP has a point. We've done similar comparisons in photography for over 40 years. I think what's lacking in scope comparisons is what is happening in photography at places like http://www.dpreview.com/ (and it's not porn ;-) )where there's a routine of tests that have visuals accompany it.

It doesn't solve the buyer's dilemma but allows some more comparison shopping to be done when hands on to every model is not available.

 

[dbooksta]

Re: Why isn't glass objectively measured?

I didn't think those were factors anymore: Every scope from the mid-hundreds up is sealed, argon-filled, and warrantied for life. If a seal breaks you get a new scope. If the reticle sticks you send it back.

Granted you get more sample defects and weaker construction on the lower-end scopes, so if you can't afford to mail back a scope then maybe that's a factor. But if you're going into a situation where you can't afford to have a scope fail you should probably bring a backup anyway, because even the best can break or get broken.

 

[One Holer]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SPDSNYPR</div><div class="ubbcode-body">I think I have understood fewer things said in this thread than any other I have ever seen posted in the English language. </div></div>

Now that's funny...

 

[Bedlam]

Re: Why isn't glass objectively measured?

Lenses can be objectively evaluated for professional photography, so I don't understand why it cannot be so for scopes.

 

[Lowlight]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: valise</div><div class="ubbcode-body">The OP has a point. We've done similar comparisons in photography for over 40 years. I think what's lacking in scope comparisons is what is happening in photography at places like http://www.dpreview.com/ (and it's not porn ;-) )where there's a routine of tests that have visuals accompany it.

It doesn't solve the buyer's dilemma but allows some more comparison shopping to be done when hands on to every model is not available.</div></div>

They have software that will take a image from a digital camera and run it through I series of tests to give you a report.

There is a quantifiable product that can be produced with photographic equipment -- rifle scopes are not that easy. I have spoken to the Ph.D that developed the software used to test cameras and lenses. In order to do anything close you would have to have a verified and qualified digital camera, and then take a series of of through the scope images after which you would subtract the camera score to try and develop the scope score. Its not as easy as that... For years I exchanged emails with him regarding this very subject. In the end it didn't help.

Again it turns into a subject review because not all eyes are created equal.

Really if you look at this site, and the reviews I have done, good or bad the companies who care take notice and make changes. Vortex for example, my "con' in their Razor was the eye box sensitivity, they went out and updated the eye piece to reduce the issue. The new Razors are no where near as sensitive as the original model. SWFA with the new SSHD Line, they pin this site to the engineers forehead to make sure they don't have the problems read about. The results, the new SSHD line is an excellent scope for the money, one of the best dollar for dollar on the market.

My feelings are, if they want a review, don't be afraid of getting your feelings hurt because if I dont like I will tell everyone. So far nobody has gotten ugly over it. A few hurt feelings, but overall no real backlash against the place.

 

[Megacab]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SPDSNYPR</div><div class="ubbcode-body">I think I have understood fewer things said in this thread than any other I have ever seen posted in the English language. </div></div>


This.

 

[valise]

Re: Why isn't glass objectively measured?

If we can attach a digital to a spotter, then surely a digital can be attached to a scope on a bench for evalutation.

Resolution I think is the tricky one.

They already measure light transmission and advertise it.

Distortion is distortion - how hard it is to photograph an optical target of squares at various magnifications like they do with photography and post it? No need for software processing as long as the review procedures are consistent and stated.

I hear LL saying it's possible, just not practical, and/or the end result is still subjective. Agreed. All reviews are subjective - but the great thing about them is over time you start to realize the common perspective offered in a reviewer.

Some are more in line with your thinking and understanding, while others are in opposition, both are equally useful over the long run.

Reviews and stats are simply bolstering a purchase decision where hands on evaluation is impracticable.

(Gotta get my count up, so I can get WTB posted, LOL)

 

[bohem]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body">
^THIS^

Great point in this post.

Take one look at the motorcycle business, peak HP sells sport bikes, but since that peak is achieved in the last 1000 RPM before the redline 99% of the squids who buy a 'busa (which won't turn much better than a Harley) or a Gixxer or any other sport bike for that matter have not the skill nor the locations to ride a bike that way. <span style="font-weight: bold">In the mean time something with a good wide midrange torque band that in real world riding is far and a way more useful will be ignored. </span>

</div></div>


Well said, and on another note, this is why I still continue to ride a 2002 R1 instead of one of the newer ones with the peak-ier more track acclimated power bands.

 

[cyrekzz]

Re: Why isn't glass objectively measured?

Yeah - not knowing anything scientific about this stuff, I would think that maybe there could be some machine, for at least the measuring of the glass, that could cover both ends of the scope and shoot a light, or laser or both and measure from start to finish to give various details about the transmission/clarity/aberration based against a set of know values of perfect 20/20 clarity??? Just thinking out loud.

 

[noname]

Re: Why isn't glass objectively measured?

with the signal processing software available any image can be processed to "mine" for specific statistics. Filters ,low, high , bypass, contrast etc. Digital camera sensors can even be preprogramed to give as an example a deeper blue (Sony) than say Nikon. Camera lens don't have funny wire thingies in them that have to do the same thing every time some decides they aren't close enough to take the shot. Camera lens can also be selected because they produce distortion, (portrait lens softening the image). " Most camera len image are repeated in a storage devise that allows comparison in the time frame. (disregading real time digital signal processing for the moment).
Human Visual process require real time processing, with such things as vector displacement in the visual cortex, that gives the time and space relation that objects seen in the visual plane. This is different with each person, (and usually better with younger people- no old snipers,fighter pilotsetc. )Even in the perfect physical optical machine that could transmit the correct wavelengths and log gain in illumination the geneic difference in rods and cones between people would cancel it out.
Sorry for the long stuff, did someone write earier "peole have different eyes?"

 

[Early Cuyler]

Re: Why isn't glass objectively measured?

Riddle me this, Batman.... How much would this testing add on to the average scope? I would imagine at least 100 bucks with 200 being more reasonable. Granted in the world of S&B and $3200 scopes it isn't as big of a deal but translate that down to the Nightforces, Vortexes, etc. and that is a sizable increase. I'd rather go to the range, take a little time, and bug people running Razor HDs and F1s instead of basing my opinion on my fuzzy interpretation of data AND paying more....

 

[threetrees]

Re: Why isn't glass objectively measured?

subjects use it, subjects will have to test it on their own.

if it's for a camera, you can make sure that the ccd is identical in all cameras, size is the same, resolution fits, etc. for a pair of eyes, this does not work.

in this sense: you can easily quantify a scope/binos/etc. but because the enduser/final measurement device/your eyes will differ from others, it - from the beginning - makes little sense to do so.

basic example: dusk; young man looks through binos 8x56 - likes them. old man looks through them, says they are dark a goes back to his 8x40 and sees better/more. why: the pupille of the old man can not open up to 7mm (beam diameter of the 8x56) anymore (age, it will hit us all). everything that his pupils don't let through is wasted. here, the 5mm beam from the 8x40 can, for him (!!), be notably 'better'.

ps: despite what others may claim, transmission, beam divergence, etc and several parameters can be measured nicely.

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: halcyon575</div><div class="ubbcode-body">How much would this testing add on to the average scope? I would imagine at least 100 bucks with 200 being more reasonable.</div></div>

To run all of these tests on a sample specimen would be practically nothing. To run them on every scope produced would definitely be less than $100 at the upper limit: In the end you're just taking a bunch of digital pictures and running some straightforward signal analysis on them.

(And since camera lens makers don't run them on every unit I assume that production variations in optics is negligible, so it's probably fair to run and publish a production sample and say, "If your scope produces different optical results send the defective unit back and we'll replace it.")

 

[Lowlight]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: halcyon575</div><div class="ubbcode-body">How much would this testing add on to the average scope? I would imagine at least 100 bucks with 200 being more reasonable.</div></div>

To run all of these tests on a sample specimen would be practically nothing. To run them on every scope produced would definitely be less than $100 at the upper limit: In the end you're just taking a bunch of digital pictures and running some straightforward signal analysis on them.

(And since camera lens makers don't run them on every unit I assume that production variations in optics is negligible, so it's probably fair to run and publish a production sample and say, "If your scope produces different optical results send the defective unit back and we'll replace it.")</div></div>

they already do this, they dont all publish it, but most of the bigger scope companies do test.

For example, last year at SHOT I saw a new prototype scope with a new lens coating and the numbers were compared to a S&B 5-25x, which advertise a resolution of, better than 3 line pars, the test S&B was actually 2.8, the prototype tested out to 2.3... as an example.

Companies do it, you just have to know where to look. Like USO in their engineering catalog used to tell you the number of lenses and the light transmission for the combination. But it's a waste of their time as it's meaningless to the average person. Like David S above, who designs and builds scopes --- of course they test their designs, but they are not sampling them after the initial design. Zeiss, Leica, S&B, etc, all test their optics and know what they will do... go to SHOT and every guy in the Zeiss booth is a Dr. X Y Z, they can fill your head with every number you want. Most talk that way to start, and the average guy at SHOT glosses over and simply looks through the scope and goes "wow" never knowing what the guy said.

 

[azimutha]

Re: Why isn't glass objectively measured?

The hard parts are that judging scope quality is pretty subjective and few of us have access to a variety of scopes, let alone ones on the high end. For the most part, I go by the observations of reviewers like Ilya Koshkin (but I keep in mind that he doesn't hunt, so I will still happily trust my NF 2.5-10X32 for actually lugging through the woods and taking reliable, humane shots on game no matter what he says about NF glass). I also pay attention to what is said about scopes or brands around here and elsewhere.

Are people saying their scopes are durable or not? Is the customer service good? Then it's considering the overall balance of features. So far, I've felt really fortunate with the choices I've made, but I've also sold a couple of excellent scopes because I learned that weight and mag range really matter to me.

 

[koshkin]

Re: Why isn't glass objectively measured?

Interesting thread.

As a matter of background: I work for a company that makes optical and electro-optical test sets for all sorts of weapon sights, thermal cameras, etc.

I can build you an automated test set that will extract every bit of measurable information on optical quality.

The million dollar question, however, is the following: will that information be of any use to you? will you be able to use it to select a scope? For most people, the question would be no.

Taking a few things already mentioned in the thread:
- lets look at light transmission. Generally, it is the most discussed and the least important major metric. I can come up with a number of cases where a scope with a higher light transmission gives you poorer image quality than the scope with lower light transmission. Or how about a situation where average light transmission is the same, but spectral profiles are different. How will that knowledge help you?
- On MTF curves: you better know how to read them. If you average the area under the MTF curve, you will successfully destroy all useful information available in those curves.
- Resolving power: how do you know what the limiting factor of the system is? is it the riflescope? or is it your eye? how are you going to account for the variations in resolving power of your eye with respect to eye pupil dilation, hydration on that day, etc?
- Distortion: why do you care?
- Aberrations: which ones do you care about the most? the least?

And the list goes on. On top of all that, why would scope manufacturers release the data they have?

If you mean to have a third party do the testing, I looked into this a little while back. There is a money problem there: the equipment and testing are expensive. Howe do you suggest a third party pays for it?

ILya

 

[Lowlight]

Re: Why isn't glass objectively measured?

If you go to S&B website for example, they have a "facts" section that explains in some broad terms what to look for, like:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> 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.</div></div>

Also there is a Twilight Factor listed in the specs for the scopes giving you a number for that scope as well as a Light Transmission percentage, so basically everything is covered there, you just have to look.

But I would read what iLya said above, as well what is repeated from David.

 

[dbooksta]

Re: Why isn't glass objectively measured?

Thank you Ilya and the other optics pros who have commented.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
The million dollar question, however, is the following: will that information be of any use to you? will you be able to use it to select a scope? For most people, the question would be no.
</div></div>

Given the interminable discussions on this forum about optical quality I assume most of the people who come here would like to have this information. Specific examples follow.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
- lets look at light transmission. Generally, it is the most discussed and the least important major metric. I can come up with a number of cases where a scope with a higher light transmission gives you poorer image quality than the scope with lower light transmission. Or how about a situation where average light transmission is the same, but spectral profiles are different. How will that knowledge help you?
</div></div>

Maybe I do a lot of low-light shooting, so I would rather have scope A with higher blue-end transmission but less overall transmission than scope B. Or maybe I'm blue-green color-blind so I can save money buying scopes with peaky transmission on the long-end of the spectrum.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
- On MTF curves: you better know how to read them. If you average the area under the MTF curve, you will successfully destroy all useful information available in those curves.
</div></div>

If I told you that the MTF for scope A is always higher than the MTF for scope B would you need to see the curves to say you'd prefer scope A? Besides, why not provide the MTF curves. Those who understand them will appreciate the data and perhaps use them to illuminate those less nerdy.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
- Resolving power: how do you know what the limiting factor of the system is? is it the riflescope? or is it your eye? how are you going to account for the variations in resolving power of your eye with respect to eye pupil dilation, hydration on that day, etc?
</div></div>

Of course each person's eye is going to be a limiting factor. Perhaps on some of these measures even the best eyes are the limiting factor. It would be nice to say, "Even if you have 20/20 healthy eyes resolving power better than 3 arcseconds at this magnification/exit-pupil/whatever is indiscernable."

OTOH, I may not know much about my eyes, but I do know that one scope is $1000 more than another, and if it provides 50% more resolving power maybe that's worth it -- either in principle, or because even if my eyes aren't good enough I'll probably eventually share it or sell it to someone whose are.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
- Distortion: why do you care?
</div></div>

Depends on the price, but if scope A is nearly distortion free and scope B has substantial distortion I'll prefer A. I imagine that for some of the full-view reticles like the horus-style distortion would impede their performance. OTOH, maybe some people like scopes with pronounced barrel distortion. I don't know, but it's easy to take a picture of a grid and provide the data so buyers can make informed comparisons.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ILya</div><div class="ubbcode-body">
On top of all that, why would scope manufacturers release the data they have?
</div></div>

Because that's the way a healthy market works. We have plenty of competing products to choose from, including multiples of every feature set you can imagine. If a company is making a good product why wouldn't they want to support their brand by releasing objective performance data?

Put another way: Why <span style="font-style: italic">wouldn't</span> manufacturers release optical quality data? Only because the data are embarrassing and they know they're commanding a market premium that their product doesn't warrant.

 

[Lowlight]

Re: Why isn't glass objectively measured?

Hmm, I see you are talking and not reading or paying any attention

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Maybe I do a lot of low-light shooting, so I would rather have scope A with higher blue-end transmission but less overall transmission than scope B. Or maybe I'm blue-green color-blind so I can save money buying scopes with peaky transmission on the long-end of the spectrum.</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
Because that's the way a healthy market works. We have plenty of competing products to choose from, including multiples of every feature set you can imagine. If a company is making a good product why wouldn't they want to support their brand by releasing objective performance data?

Put another way: Why wouldn't manufacturers release optical quality data? Only because the data are embarrassing and they know they're commanding a market premium that their product doesn't warrant.</div></div>

Both of these were answered in detail:

Manufacturers offer it, not on "sales" websites but on "their" websites, you just have to look.

Examples,


Optical data
Magnification: 5 - 25x
Field of view @ 100m: 5.3m - 1.5m
Exit pupil: 10.95mm - 2.28mm
Eye relief: min 85mm
<span style="font-weight: bold">Twilight factor: 14.1 - 37.4
Light transmission: min 90% day & night</span>
Diopter setting: +2 to -3

or even better,

Everything you asked is provided by the manufacturer, at least some. you just have to look.

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Everything you asked is provided by the manufacturer, at least some. you just have to look. </div></div>

That's more information than I've found from any manufacturer anytime I've looked. Whose data are those, and where did you find them?

In any case, even that is less than what I (and others in this thread) suggested we should expect. 90% transmission is a lower bound I suspect all but the cheapest scopes meet, and they do not give transmission by wavelength. Resolution is a start, but in that domain we were looking for MTFs. No other optical quality specs are provided in what you found.

 

[S12A]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"> No other optical quality specs are provided in what you found. </div></div>

because nobody cares? optical clarity is great and all , but for tactical optics overall strength and repeatability are the important thing. its like rifle manufacturers offering certain MOA guarantees... just because it can shoot .25moa can you? just because a machine registers a level of optical clarity / distortion , will you be able to see it.

that is why people take the time to get their hands on scopes and review them individually , its the package that counts, not a number that the manufacturer is citing.

 

[calling4life]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">I'm so sick of reading subjective evaluations of glass quality in riflescopes. Why isn't this something that is objectively measured? AFAIK the only optical characteristics of a scope that matter are:

1. Resolving power
2. Light transmission across the visible spectrum
3. Distortion

We expect any decent company to list reticle adjustment range, exit pupil and eye relief. Why not these other parameters?
</div></div>
Why isn't glass objectively measured?

Let me answer that by asking you this; Why aren't women?

 

[dbooksta]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: calling4life</div><div class="ubbcode-body">
Why isn't glass objectively measured?

Let me answer that by asking you this; Why aren't women? </div></div>

Maybe you run in more refined circles than I, but whenever we discuss women the first questions most men I know ask (one way or another) are objective measures: Age, height-weight, Hip-Waist-Bust ratios, colors, etc.

Of course you're not going to marry a woman based on these alone, but they're the context we expect before discussing the more subjective features of a woman.

Like Anthony box said, it's the package that counts in the end, but I don't have time or access to test "the package" of all the contenders for my dollars out there. I appreciate the informed and expert opinions of those who do have time and access, but those are always colored by their budget, skill, and "utility functions" which may have nothing to do with mine. The more objective screening criteria I can weigh the better.

To his example: Even if I can't shoot .25MOA, I might buy a rifle guaranteed to .25MOA for several reasons:
1. I don't want my equipment to be the limiting factor in my performance.
2. It's a measure of quality. It not only helps me narrow the otherwise vast field of similar rifles, but it also helps me put the gun's price and value in a more firm context.

 

[koshkin]

Re: Why isn't glass objectively measured?

dbooksta, here is a question for you:

Let's consider two hunting scope that Kahles used to market here. There are identically configured: 3-9x42 with one inch tubes. One is Kahles KX and another is Kahles CL. Let's say, I take both to the lab and run light transmission tests on them. Afterwards, I provide you with two curves of spectral transmission. Those curves will look very similar to each other (these are fairly similar scopes), except the light transmission on the KX model will be slightly higher than on the CL model at every wavelength. Which scope would you choose out of these two for low light hunting?

ILya

 

[dbooksta]

Re: Why isn't glass objectively measured?

Without knowing anything else, the KX. (Though if I knew the prices and difference in transmission values I may still decide the KX isn't worth a premium.)

 

[koshkin]

Re: Why isn't glass objectively measured?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">Without knowing anything else, the KX. (Though if I knew the prices and difference in transmission values I may still decide the KX isn't worth a premium.) </div></div>

Actually, between the two, KX was a somewhat cheaper scope and while very good, in terms of actual performance CL was a better scope in every way possible. It had a more sophisticated optical system with a larger number of lens elements which was responsible for lower overall light transmission. However, it did provide better image quality.

Imagine you are a product line manager at Kahles and you have these two scopes. You've got a bunch of technical data on your hands. If you release that data, you will spend 80% of your time trying (usually unsuccessfully) to explain why your more expensive scope has lower light transmission.

Then you will field other questions with 95% of them being a result of user error. For example, the CL model is equipped with a side focus knob, while KX has fixed parallax. I can virtually guarantee that more than half of all complaints on the image quality of the CL model will come from a simple fact that an average hunter is too lazy (sometimes too stupid, but usually too lazy) to figure out how to properly set up eyepiece focus so that the side focus can be used properly. And if, God forbid, you release the MTF curves (for a few magnification settings), you might as well turn off your phone and stop checking your e-mail. The people who can understand the information in MTF curves can usually figure out if the scope performs to their liking anyway, while the people who think they understand MTF curves and really do not will drive you absolutely insane.

The biggest problem with all this is that the people who will give you the most trouble are usually the ones with the shortest attention span, so they are effectively not trainable. If you could tech people to understand technical data, perhaps it would be worth releasing. Unfortunately, in most cases you can't.

I gave a few talks over the years on how to pick scopes, what to look for and what is important from an optical perspective. As a result of those talks and of the typical questions I get on the subject, I wrote a 15000+ word article on the fundamentals of riflescopes. This is about as short as I can make it without either dumbing it down excessively or skipping major topics. I constantly get questions explicitly covered in that article from people who claim to have read it. Careful probing suggests that they briefly looked at it and were too lazy to put any effort into actually reading it. As it turns out, they have no actual interest in learning how to come up with the answer to their questions or to even figure out how to ask the right questions. They want answers and they want them immediately, usually before they know what question to ask.

These people are probably a small minority of all riflescope users. However, they are vocal and incredibly time-taking. If you tell them to go pound sand, they will be all over the internet slinging mud faster than you can imagine. If you give them a precise answer they will not understand it, so they will be all over the internet screaming that they just got told a bunch of mumbo-jumbo that made no sense to them.

It is damned if you do and damned if you do not. If I were a product line manager for a riflescope company, I would simply hide behind the "Proprietary" stamp vast majority of the time simply because it is the best option available out of a bunch of crappy ones.

I am not associated with any scope maker. I field a lot of question on scopes largely because I like talking about them. Occasionally, I get tired of answering the same question from the same person and ask him to look into what I wrote on the subject elsewhere or to start an open thread so that I could answer it there once and for all. More than half the time the person calls an arrogant bastard (or something along those lines), which tells me everything I need to know about instant gratification.

ILya

 

[dbooksta]

Re: Why isn't glass objectively measured?

Thank you Ilya. I think you've given good reasons why manufacturers haven't released technical data.

Note, however, that the data aren't "proprietary:" Anyone can take a sample and run it through all these tests. I like valise's mention of dpreview.com, which has done a great deal of this for camera glass.

And I like the way at least some camera lens makers have done a lot more in terms of publicizing this information. Why does one lens cost $1500 when another with identical speed and range costs $500? Here are the MTFs. Heck, they'll not only tell you how many lenses are in the system but even the type and function of each. Even if you don't understand these data at least you have something concrete backing up the experienced users offering their subjective, "that $1500 glass is way sharper at all apertures."

Granted, I imagine there are a lot more professional photographers than professional shooters, so maybe your point is that you need an expert user base of a certain size to make these data worth releasing. Heck, the camera user base is evidently large enough to support significant <span style="font-style: italic">third-party</span> objective testing of lenses. Are rifle scopes that fringe of a market?

If the reason manufacturers don't provide better optical data on 4-figure scopes is that shooters are, on the whole, too stupid or immature to handle it, then that's a damned shame. If the reason we don't have third-party analysis is that the market is too small, then shoot.

Perhaps we could provide a "safe-harbor" warehouse for this information online: Manufacturers, third-party testers, and anyone: submit your optical data to be served up by the scope warehouse, and then disclaim any responsibility for "supporting" those data. I.e., if somebody calls to discuss your MTF curves, do what you do to me when I call asking for even basic figures like resolving power: Say, "I don't know if we have those numbers; I'll try to see if somebody in engineering does and never get back to you."

Like you said, a lot of buyers never look for the data, and those who do may not know what to do with it. But there's a lot of us with engineering degrees and know-how who think long and hard before dropping 4-figures on a scope. And we don't all have the luxury of lining up $20k worth of candidates in circumstances where we can subjectively evaluate their relative optical merits. And we shouldn't have to given that objective measures can tell us what we're looking for.

 

[Lowlight]

Re: Why isn't glass objectively measured?

Cameras have a $300 program of which you run the picture through software, and it gives you the data you are looking at dpreview.

Again, you might be looking but you aren't paying attention. I spoke to the Ph.D author of the program used. I discussed at length the possibility of doing this for rifle scopes. In the end, it was not the same.

Here is his link, I spoke to this guy on several occasions

http://www.normankoren.com/Tutorials/MTF5.html

He has software for this, it's not a one step process, and when you put a scope between a camera and the subject you run into several negatives that are not related to the scope.

Here is the image test software link

http://www.imatest.com/

If you think you can do it, buy the $300 program called Image Test Studio and let us know how it works out for you.