The Tiffen 4 x 4" Full Spectrum IRND 2.1 filter is a combination of an infrared control filter and a 2.1 neutral density filter. An IRND is ideal for HD cameras, which have increased sensitivity in low light and, consequently, increased susceptibility to infrared contamination. When using a standard neutral density filter to counter the increased light sensitivity offered 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 infrared light leakage reaching the sensor whilst maintaining the additional exposure benefits of a neutral density filter. This filter is constructed from Water White glass and is manufactured using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and polishing it to a tolerance of 1/10,000th of an inch. This filter measures 4 x 4" / 101.6 x 101.6mm. - Infrared control filter helps block infrared pollution affecting colour fidelity of images; this allows for a wider colour gamut and more accurate colours, particularly noticeable in dark areas of the image. - 2.1 neutral density filter provides 7 stops of exposure reduction. - Water White optical glass for excellent clarity. Specifications