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HD - High Definitio

PHD COMP 2Hoya's HD filter range is uncomparable. By the quality of this filter class you can tell that Hoya is the world's eminent optical manufacturer. Their knowledge and experience and their unequaled production facilities come together in this wonderful product.

Hoya HD filters carry no less than 8 layers of coating. That is: on both sides of the glass. It must be clear why this is. High grade multi layered coatings greatly improve the filters characteristics. As a result the Hoya HD filter transmits 99,4% of the light. Which is far less obvious than you might think. The windows in your house may transmit no more than 70%. Of course the transparency depends greatly on the thickness of the plane (or tho planes in the case of isolation panes), but it's a fact that glass will never transmit 100% of the light. Hoya's 99,4 is an incredible good performance.

Hardened glass and hardened top coating

Due to the chemical composition and special production techniques, the Hoya HD glass is four (4) times more resilient than the glass types of other brands. So it is much harder to scratch and that is good news. Furthermore the top coating layer has been 'backed' on top of the other layers, which gives this coating nano-technology-like properties. It is much harder than an ordinary coating and without pores the surface is absolutely smooth. Grease, water drops, fingerprints, dust or mud, they all can be easily wiped off. With hardly any effort and (!) without much risk of scratching the surface.

Mount

Filters of other brands, and other Hoya classes, use springs or screw rings to mount the filter glass inside the ring. For the HD class Hoya employs a far more advanced and better technique: heated pressure mounting. In an impressive automated machine, the empty filter ring is heated as a result of which it will expand a little. The filter glass (already polished and coated) is held in the opening. Rims in the inside of the filter ring are then carefully compressed to the glass, which pinches the pane firmly and immovably into the ring. When the ring has cooled down, glass and ring have integrated into one strong unit. From the perimeter of the glass, assimilated in the ring, no light or moist can reach the edges of the pane. Especially for a polarizing filter this is a great advantage.
The high pressure mount also makes a HD filter ring ultra-slim. It measures no more than 4,25mm (5mm for a polarizer). This makes HD filters very well suited for (ultra) wide lenses.