The Tiffen 4 x 4" Hot Mirror IRND 0.9 Filter is a combination of both a hot mirror infrared control filter and a 0.9 neutral density filter. A hot mirror IRND is ideal for HD cameras, which have greater low-light sensitivity and, subsequently, an increased susceptibility to IR contamination. When using a standard neutral density filter to counter the increased light sensitivity afforded by the HD sensor, the effects of infrared pollution become more apparent. This filter combines an ND filter with a comparable IR control filter to eliminate the spill of infrared light reaching the sensor while still maintaining the extra exposure benefits of a neutral density filter. The hot mirror filtration incorporates a dielectric mirror in order to combat the effects of both near and far infrared regions of the spectrum.
This filter is constructed from Water White glass and is made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding flat to a tolerance of 1/10,000th of an inch. This filter measures 4 x 4" / 101.6 x 101.6mm.