Schneider 4x4" ND 0.3, Neutral Density Professional Glass Filter.
• Neutral Density: Schneider Neutral Density (ND) filters are designed to control exposure or depth of field under various lighting conditions without affecting color or contrast. Unlike other brands, Schneider Absorptive ND filters are a neutral gray, achieved with laboratory precision.
• Diamond cut from crystal-clear, water-white optical glass, Schneider filters are ground and polished to a precise flatness and plane-parallelism (exact parallel relationship between front and back filter surfaces). Then, to ensure perfection, this is verified by a laser interferometer. Schneider filters are then checked with a densitometer for consistent density, and tested with a spectrophotometer for proper light transmission. It's due to this ultra-high consistency, that allows cinematographers to swap like filters mid-shoot with no discernible variation in color or effect. What's more, the unprecedented purity, color saturation and repeatability of Schneider filters virtually eliminate the need for lab color timing correction.
• Schneider filters stand up to the most rigorous demands on set or location. Manyfeature Schneider's specially formulated hard anti-reflective (AR) coating to resist flaking, peeling and scratching. This proprietary coating also reduces light loss and flare to less than 1% per surface, compared to untreated glass that has a light loss of 4% per surface. Schneider screw-on filters feature virtually jam-proof brass precision mounting rings, while unmounted Schneider laminated filters are protected against delamination and edge-chipping by Schneider's unique Edge Seal, which also reduces edge reflection and edge flare.
• The common perception among photographers and cinematographer's is that filters should not be used in front of long length lenses, due to the critically short depth of field of these lenses. This belief is often confirmed when poorly made glass or plastic-resin filters are placed in front of a long lens, and the degradation of the image is visible simply by looking through the viewfinder. This degradation is caused by poor quality control, low-quality glass and poor glass grinding and polishing techniques used in the manufacture of such filters. Schneider filters have no such problems, and can be used in front of even the longest lens.