Have you ever wondered how do they test lens coatings? A lot of rubbing it turns out. Lenses are rubbed 20,000 times with a 'linear abrader' and microfibre cloth. Then the lens surface is measured in term of contact angle: the higher the score, the better the cleaning properties.

Hoya's Diamond Finish Coating has been selected as the best lens coating by NSL Analytical Services, an independent laboratory in Ohio. The results showed that Diamond Finish preserved its dust-, dirt-, water- and grease-repellent properties even after long use and repeated cleaning.

In rigorous tests of premium coated lenses simulating real-life wearing conditions, Diamond Finish out performed its competitors on all three features shown to be of primary consumer concern: durability, clean ability and scratch resistance. Lens performance is compared to an ISO reference lens and given a value in terms of scratch resistance. The final score, known as the Bayer value, was 29% more durable that the second place getter.

For us this confirms our experience - the Diamond Finish is a good performer, the best Hoya coating we have used.