Lens coatings have become as much of a concern as the lenses themselves, these days. There’s plenty of choices when it comes down to it, and you really want to know what it is that you’re buying, and what kind of performance you can expect from it. This is where it does make sense that the ‘brand name’ coatings are popular. They give you a better idea of what you’re going to be able to expect from the way the product behaves when it’s out there in the real world. One thing that this mentality leads to, however, is confusing consistency with quality.
Quality vs Consistency
Consistency can be a great thing, but you need to know what your limits are when you’re considering how it applies in any given circumstance. For example, if you know that your brand-name coating is definitely going to craze when you leave sunglasses on the dash of your car – well, that’s consistent. You don’t want them to do that, of course, so maybe in that instance having consistency isn’t a good thing. It lets you manage the failure when it happens, of course. I told you not to put them on the dash of the car!. But you don’t really want to be in that situation in the first place. You want the lenses to work and not have a problem. No matter what kind of abuse they get subjected to, you really would prefer the coating doesn’t get scratched, crack, craze, or do anything.
You can usually get a pretty consistent meal from whatever McDonalds or other fast food chain you go to. No matter where you get it from, you’re getting the same thing. Which is again, both good and bad. You know what you’re going to get (more or less), but you also know where the quality of it is going to be. It’s not like you’re going to order your usual McHeatAttack at a different restaurant and they’re going to suddenly going to use real meat instead of compressed cardboard and newspaper. No – ingredients and process remain the same, so that way consistency and ‘brand integrity’ is maintained.
As with AR coatings – your branded products need that same consistency from lab to lab, and usually a lower standard of quality is easier to maintain across multiple locations. If you look at the ‘top tier’ of branded products from some manufacturers, for example, you can see this. Most labs are only allowed to produce the ‘lower tiers’ in-house, and have to outsource the highest-quality stuff to a central location to get produced. That’s an indication that the process may be a little too involved and costly for your every-day lab to manage. If it’s quality that you’re really looking for, then it makes sense to find labs that can do a top-tier coating themselves, since that can be an indication that they’re committed to producing the best quality they can, and not just the middle-of-the-road options.
Not Created Equal
One problem is that there is often a very broad brush when it comes to AR coatings. We have maybe three major brands, and then everything else that’s not a ‘name brand’ gets lumped together into one category. Usually with some negativity attached to it. This is very common for ‘house brand’ AR coatings. For some reason, trying the house brand of a lab once, ten years ago, is enough for someone to classify “all house brand ARs ever are terrible”. This just seems to make very little sense to me. Obviously, you can get bad stuff. But that doesn’t mean that all places product the same kind of product. Just because it doesn’t have a fancy name attached to it doesn’t mean that it’s junk.
A Solid Base
Hard coating plays a very large part in the AR process, whether or not you knew that. That’s the ‘bedrock’ of the AR coating, and it makes a huge difference on how any coatings that are applied to it behave. There are really two types of hard coat processes – a ‘spin coat’ or a ‘dip coat’. Generally, the spin is quicker, but can be more prone to problems during the life of the lens. The dip coat process takes longer, but can yield much better long-term performance for lenses.
Knowing what kind of processes your coating uses can help give you an idea of how it might perform in the future. The dip coating tends to be a more uniform thickness, which helps it be more resistant to crazing. This happens because heat (like being left on the dash) can cause the hard coat to expand. If the coating has larger variances in thickness, it expands unevenly. This makes the AR coating on top of the hard coat more likely to crack.
When the hard coat layer is even, the coating will expand at a more uniform rate, which reduces the likelihood that the AR coating on top will have a problem. A dip coating also tends to be more scratch-resistant, as the coatings using in a spin coat are normally cured using a U.V. light source, while the coatings used for a dip coater are usually baked in an over. This allows them to use different hard coating chemicals with different properties and performance characteristics. This is something that you should be aware of – all ‘hard coating’ and ‘AR coating’ are not the same. It’s just like saying that one pair of ‘glasses’ or ‘frames’ is the same. There’s a lot more that goes into it, and you are better served by knowing the differences so you don’t get an inferior product.
Process is King
The process that’s used in applying AR coating can vary wildly depending on where you get it from. This is what matters. The sticker on the bag doesn’t mean anything – it comes down to how well the lab applying the coating knows what they are doing, and how well their process is set up. If they cut corners, you’re going to have a bad time, no matter what kind of equipment they have.
If we look at dip-coating, for example, the lab is going to need a process for making sure the coating sticks to the front as well as the back of the lens (since it’s getting completely dipped in coating). That means a lot of know-how has to go into making sure every lens from every manufacturer works, because all of THEIR hard coats are different. This has to be done, otherwise there’s a risk of coating failure, which nobody wants.
Even cleaning can be a problem. AR coating basically deposits very thin layers of materials on the front of the lens. Even a tiny speck of dirt on the lens, and it gets trapped there forever. Like a mosquito trapped in amber, except in this case it can’t be used to create new dinosaur populations. It just pisses you off because it looks like a pit in the lens.
If you have a lab that has a ‘big brand’ coating as well as their own ‘house brand’, you can usually tell the quality of the house brand really isn’t any worse than the big name brand. That’s because it’s not about the AR coating itself – it’s about having the mentality to correctly process the coatings and not have problems. Often, big brand names will help get a lab ‘up to speed’ or to a minimum level of standard. Once they get the process down, the actual brand of the coating they sell becomes less relevant, as they have all the building blocks of successful coating in place.
The take-away from this is that coatings are going to be different from every single lab. The only way you’re going to know what you are going to get is to try some out. You shouldn’t just assume that they are going to have a bad product just because you haven’t heard the name. Or because maybe you didn’t like it five or ten years ago. At the rate processing technology is changing, a lot can change in a short period of time, especially when it comes to improving quality and process control.
If you’re thinking about trying a new product – then do that. Do your homework on what a lab can offer you. Get an idea of what kind of equipment they have, and how good they are at doing things. If you educate yourself about how coatings work, you can make sure you’re giving your patients the best quality products. You don’t need to jump in blindly, but go ahead and take a lens coating from and independent lab and put it up against a brand name coating. See how they work for you and make your own decisions.