This B+W Infrared Filter blocks the entire visible spectrum, so to our eyes it looks completely opaque. Unlike the infrared filter described above, it makes pure infrared photographs possible without the visible red component. Its transmission only begins to exceed 1% at 800 nm, rising to 88% at 900 nm, and remains that high far beyond the upper limit of sensitization covered by infrared films. This filter is used less frequently in pictorial photography because of the dramatic loss of effective ISO. But in the scientific field, materials research and forensics, the limitation to a strictly infrared range is often important. The filter factor is very dependent on the illumination and on the characteristics of the film.