The B+W ND.3 Neutral Density Filter attenuates the light by one f-stop (log density 0.3), which can be beneficial, for instance, for the correct exposure of high-speed films when the brightness of the subject is still too high for the fastest shutter speed and the smallest aperture. It is recommended especially as a complement to B+W Neutral Density Filter 102 for fine adjustments. The filter factor is 2x.
This filter uses the 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.
Each 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%.