The bw 58mm black 093 infrared filter blocks the entire visible spectrum so to our eyes it looks completely opaque iit 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 sensitisation 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