The Tiffen 4 x 5.65" 80D Hot Mirror Filter is a combination of both a hot mirror infrared control filter and an 80D color temperature correction filter. HD camera's without an infrared control filter benefit from greater sensitivity to the red area of the spectrum, however in order to achieve this they are also more susceptible to infrared pollution; a hot mirror counters this by blocking infrared radiation from reaching the image sensor and maintaining truer color fidelity. This increased red sensitivity also results in overexposure of the scene when photographing under warmer, tungsten light. The combination of an 80D filter balances the light to daylight values with less exposure compensation required than if done in-camera.
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 5.65" / 101.2 x 143.5mm.