Tired of blurred vision due to a defective lens surface?
You are not alone… As the most popular laboratories in the country have this problem, we decided to withdraw and offer our customers anti-reflective and anti-scratch coatings from Hoya Japan.
One of the most important things to understand about this subject is that lenses have what is scientifically called a coefficient of thermal expansion. It's an elegant way of saying that lenses expand and contract with temperature.
When the glass expands and contracts at a speed different from that of the coating, it can, and very often will, crack. Keep in mind that the ultra-rigid anti-reflective coating is very, very thin compared to that of the glass underneath.
What does the surface defect look like? Is it everywhere or located in the center and in the shape of a circle? Are the cracks vertical, horizontal, circular or sporadic? The shape of the cracks will tell what caused the cracking in this particular case.
A very good coating is not necessarily the hardest, but it expands at exactly the same rate as the base material. The more glassy the coating, the greater its possibility of cracking. Unfortunately, this is often the case. Several laboratories persist in selling treatments that are too stiff and inflexible.
Heat is the problem, almost always! Hot tap water has destroyed thousands of lenses in recent years. We understood this by asking the victims questions:
Q. Were your glasses left in the car? No.
Q. Placed in checked baggage at the airport? No.
Q. Worn in a sauna? No.
Q. Is there any reason why you might think they would have heated up? Well hmmmmm. I clean them every day under hot water. I let the water get as hot as possible, then I clean them.
Avoid, even with Hoya lenses ; )