ARRI says that they've been inspired by all the high expectations of modern durables, industry image quality and a growing demand for top-quality external filters to introduce their own external Full Spectrum Neutral Density (FSND) filters.
ARRI isn’t a stranger to FSDN filters, having created filters that come built-in to their ALEXA Mini and AMIRA cameras, but ARRI wants to push forward with their filters, in particular to prevent diminished perfromance of ARRI cameras due lesser-quality external filters.
So what’s different about ARRI’s filters? There are a lot of other external filter out there. ARRI believes that their filters will stand out because they are c-shaped instead of the typical square shape. “Different from most competing external filters which have square, bumpy edges, the edges of the ARRI FSND filters are perfectly c-shaped. This curved edge reduces glass chipping and makes for easier and safer mounting,” says ARRI
The glass of the filters is promised to be flat on both sides, meaning that the two sides are completely parallel to each other. “The glass 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 areas of the focal plane can become soft.” The filters are meant to reduce the amount of light entering the lens, which would allow for wider aperature — and therefore a shallower depth of field — in bright conditions while avoiding overexposure. That shallower depth of field makes it especially important that your filters don't inhibit accurate focusing across the image area.
ARRI’s new filters will also be colored black to prevent light from scattering and will use various coatings. “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.” All of these coats should prevent water and grease from actually sticking to the surface of theglass and also make the filters scratch resistant.
The filters come in a variety of stop ratings and sizes. You can get more info on arri.com.