ND filters are designed to continuously reduce light transmission.

The absorption factor of these filters is approximately 9 stops.
Thanks to their quality, Hoya filters are totally free from color casts.

Hoya HD filters represent the "state of the art" in photographic filters, and are characterized by:

• 8-layer anti-reflective coating on both surfaces of the optical glass.
• 4 times higher resistance to breakage than a conventional photographic filter. This result was achieved thanks to the adoption of particular hardening treatments that Hoya has developed to make its ophthalmic lenses compliant with ANSI Z80.3.2001, required for the marketing of prescription lenses in the USA. This hardening treatment is also very effective in preventing scratches.
• Stain-resistant treatment that makes the filter surface much easier to clean and resistant even to indelible inks.
• Ultra-Slim frame made of high-stability aluminum, treated with "black-alamite" external finish. The filter is therefore suitable for mounting even on ultra-wide-angle lenses, without vignetting at the edges of the image.
• Black lacquer on the outer edge of the filter, which prevents internal parasitic reflections even in the most treacherous backlighting.
• Knurled edge that facilitates the mounting and removal of the filter.
• Front thread that allows a second filter or lens hood to be mounted.
• Round filter case with bayonet closure.