B+W's Series 8 Strong UV Absorbing Filter is a sharp-cutting, nearly colorless B+W filter that blocks UV radiation up to the limit of visible light. It is used in ultraviolet fluorescence photography for the prevention of unsharpness caused by the intense UV illumination (which is due to chromatic aberration in the UV range). It can also prevent the fluorescence that may occur in the cement between lens elements. Because of the usually rather colorful fluorescent subjects, the delicate yellow cast in color photographs is negligible. Its filter factor is 1.
This filter is uncoated. Uncoated glass is usually found with special effects filters and acrylic filters, where coating is either an impossibility or would work against the effect the filter is trying to attain.
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 its 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.
Note: diopters are mounted in the older mount due to glass thickness.