Your eye is not as calibrated as you think…
Scope reviewer often pride themselves on telling you which high end optic out there has the “Best Glass”. They devise all sort of ways to demonstrate the glass quality of a particular scope, in hopes of lending credibility to their observations. Is Scope A truly better to see through than Scope B ? That is the first question when a new scope hits the market. Doesn’t matter it retails for $4000+ people want to know about the glass.
I am here to tell you, for 90% of the scopes out there, particularly the higher end ones, you’ll never see the difference. We are talking microns and nanometers when it comes to quality differences.
Over the years Sniper’s Hide has put less focus on the quality of the glass and more focus on the mechanics of the scope. Why do I constantly dismiss the glass quality question ? Well that is very easy to answer. I have seen behind the curtain and know better than to comment on something like glass quality. These are optical prescriptions designed by engineers to meet a spec, and with modern techniques, machines and computers, they can hold tolerances in the 25 to 5 Micron Range. To me, that far beyond what an eye test can determine.
Make no mistake, if you are looking through a scope at an object or chart, you doing nothing more than a glorified eye test. What you have determined is how well “You” the end user can see that object under the current conditions. It’s no different than going to your eye doctor and choosing “Better or Worse” but with a lot less variation.
Everything out of the box looks great … it’s how you use it determines whether that optical design is suited for your needs.
Thankfully, Vortex Optics gave Sniper’s Hide a 3 day behind the scenes tour of the factory in Madison Wisconsin. They have a state of the art facility and this being our 5th scope factory tour over the years, I can tell you from first hand experience they have pulled out all the stops when it comes to investing in equipment.
Being able to visually see and demonstrate what some of us have known for years is huge. They have all the latest computer controlled testing equipment which goes way beyond what the human eye can register. They opened their doors and allowed our cameras inside, explaining each step along the way. Nothing was off limits.
One machine can tell you everything you need to know about a scope in the time it took me to write this paragraph. Not only do they use this type of equipment to test their products, but they also test other companies scopes to compare. It’s this comparison that many manufacturers use to help level out the competition. They all know who is considered the top scope, and they all work to meet or exceed those tolerances.
Regardless of the amount of time spent behind a machine or in the room with all that high end testing equipment. Not one engineer wings their opinion about a particular optic. It’s all left to the equipment and nothing is taken for granted. If you look at the desks around the Vortex Factory, each one has a collimator on them. I saw a man walk off the street and hand over a scope he thought might have an issue. The first step was to put it on the collimator sitting 10 yards from the main door. These are calibrated units designed specifically for rifle scopes.
Where Errors can exist which detract from the Optical Quality
Now nothing I’m saying is meant to be a blanket statement. There are exceptions to the rules and you can find a scope that will have a problem which degrades the optical quality. That can come from poor assembly practices which misalign a lens cell, or from a very low quality scope that just was not spec’d out as well in order to save money. The later are usually sub $800 scopes but even then, it’s not a guarantee. Most of the current manufacturing processes do not index the lenses on the parallel faces but rather use the rough edges for mounting. This can cause variations in the cells. That use of the edge mount can account for small degrees of misalignment, giving Scope A a better picture than Scope B. Not the lens package but the mounting and assembly.
The glass used is pretty consistent, how they design the optical prescription for that scope matters. The coatings will determine whether you can see better at dawn or dusk when comparing scopes, but overall in the bright light of day, We’d be hard pressed to see the difference. So if you’re gonna review a scope, do the optical test as the sun is setting and see which retains the light better than the other. Remember settings and adjustments matter.
The biggest issues when one finds one scope working better than another of similar quality is usually how it has been set up. Each person is different, so the scopes have to be properly adjusted to work as advertised. Understand the Ocular adjustment to focus the reticle can alter the magnification of the scope by as much as 5x or more. Yes you read that right, if you don’t adjust the ocular lens for the user, you can effect the optical design so one scope will “look” inferior to another who’s adjustments might not be altered. We can take two of the same scopes with measured compatibility and by moving the ocular adjustment of one, give the other a noticeable advantage. That is why those unfamiliar with the mechanics of a rifle scope can choose a scope of lesser quality.
It’s important to know what is in our power to check and what is beyond our reasonable comprehension. In my opinion, glass, under normal circumstances is not worth discussing. We can create a situation like lowlight, to tell if one will work for hunting vs another, but before you do, read up on the exit pupil size of the scope. You may find one scope will work on 10x for lowlight shooting and other needs to be at 8x. And just by lower the power of any scope you might find a better sight picture than you thought.
We’ll talk about glass more moving forward and explain why one optical design with lenses from Schott is no better than another designed with lenses from Hoya. It’s really not about the source of the glass but the combination of lenses within the prescription as both will use glass elements of different types to add and subtract from. It’s not the source, but the how the engineer assembled them. In many cases what people believe to Schott Glass is actually only used for prototyping and not for the production model. Once the design is established it’s pretty easy to source glass of the same spec from other places.
Check your scope’s mechanics, do tall target tests, see if it repeatable on a known distance target. Riflescopes are a sighting system and not used for bird watching. The mechanics matter more as I can say with more years behind a scope than I care to admit, very rarely did the glass quality cause me to miss a shot. To take it one step further, the Unertl MST–100 was originally sold to the USMC for $700, do you think the glass quality of that scope was on par with today’s $3000+ scopes ? Doesn’t matter to a collect the MST–100 can go for more than $5000 at auction. What matters was, it was built in a barn in Pennsylvania with no real clean room or modern machinery to speak of… yet it served from 1978 until the early 2000s. People covert this scope and nobody ever questioned the glass quality.