This B+W Neutral Density Filter reduces the light by two f-stops (log density 0.6), and it is the most popular ND filter in photographic work. It offers many benefits, for instance f/4 instead of f/8 for selective sharpness instead of a great depth of field, or 1/15 s instead of 1/60 s for a flowing instead of a “frozen” waterfall. It has excellent color neutrality, costs less than the denser filters, and is recommended as part of a basic outfit. The filter factor is 4x.\n\nSingle Coating\nEach glass surface is vacuum coated with one layer of Anti-Reflection coating. This single layer helps to prevent internal ghosting and reflections. It also improves light transmission from approximately 92% (uncoated glass) to over 98%.\n\nThis filter uses our standard B+W F-Pro filter mount, which has a front accessory thread and is made of brass. Compared to the earlier standard mount introduced in 2001, the F-Pro mount has become thinner. Now it can be used with wide angle lenses, including most 24mm focal lengths on a full frame body, without vignetting. Another advantage of the F-Pro mount is it's modified retaining ring, which is no longer threaded in from the front, but holds the filter glass in place from the back. When removing a filter or lens hood that has been screwed on too tight to the filter, the retaining ring is not at risk of loosening.\nNOTE: diopters are mounted in the older mount due to glass thickness.