Not all ND filters are created equal

Arri FSND filter
Neal Romanek
August 24th 2017 at 1:03PM : By Neal Romanek

The new pro filter features hydrophobic and oleophobic coating, and a reflectivity rating of 0.2%

Arri has released its own FSND external filter. Arri Australia will have the first demo set of the new neutral density filter in September.

The Arri FSND filter comes in 6.6in x 6.6in and 4in x 5.65in sizes. The optical quality, Schott B270i glass used in the Arri FSND filter is polished completely flat on both sides of the filter with completely parallel surfaces. Plane parallelism is especially important when using a wide-open telephoto lens, as otherwise areas of the focal plane can become soft. FSND filters reduce the amount of light entering the lens, allowing the filmmaker to shoot at wider t-stops under bright conditions without overexposure. FSND filters also make it possible to blur moving elements such as water or traffic in bright conditions.

The edges of the Arri FSND filters are curved to reduce glass chipping and to allow for easier and safer mounting. The filter edges have also been coloured black to prevent the scattering of light. Close to the filter’s edge, the glass surface also features an engraved unique Direct Product Marking (DPM) which will improve inventory security at rental houses and with individual owners. This GS1 bar code, which is readable by most camera-based bar code readers, makes rental check-ins and check-outs easier, provides proof of ownership, and eliminates the need for stickers that can fall off or leave residue on the filter.

Multiple layers of ND coating, anti-reflective (AR) coating, hydrophobic coating, oleophobic coating, as well as a final “hard” coating have been applied to both sides of the filter. A normal air-facing filter has a 4% - 6% reflectivity rating at each air-glass surface, but ARRI has been able to achieve 0.2% reflectivity.

The additional coatings, hydrophobic and oleophobic, keep water and grease, respectively, from adhering to the glass, cutting down on cleaning time. The hard coating, used to prevent scratches on the filter, is durable and resistant to wear and tear.