The 4 x 4"Tru-Cut Ultraviolet (UV) Infrared (IR) 750 Blocking Filter from Schneider Optics has a completely colorless glass carrier coated with a number of extremely thin, partially reflecting layers with precisely computed thicknesses, similar to MC coating (multi-coating).
The Schneider Tru-Cut IR filter does not block by means of absorption, but by interference of the unwanted UV and IR radiation that is repeatedly reflected between these layers affecting the wavelengths on both sides of the visible spectrum with a steep cut-off. This filter is particularly effective when using high-density neutral density filters that help control depth of field. As the iris on the lens becomes larger, the danger from IR contamination becomes more prevalent. By using this filter, colors become more vibrant and true.
The purpose of this filter is to block all UV and IR 'light' from reaching the sensor. This is particularly useful with some high end video cameras on the market that leak IR and produce magenta blacks in low light - this filter will bring the blacks back to black. The filter is clear when you look through it at 90° but when you look at it from an oblique angle, it has a magenta or cyan cast due to the complex coatings.
Used mainly on digital and video cameras with CCD sensors without an integrated IR protection filter, because the IR sensitivity of the CCD sensor would otherwise cause color changes and unsharpness
That unsharpness results from the chromatic aberration of the lenses that are only corrected for visible light
In the visible range, the transmission curve is very high and straight