It allows pictures of a pure red image while making good use of the relatively low sensitivity of infrared films.
Filter factor is approx.
This black infrared filter will filter out the entire visible spectrum. Filter factor is determined by the film's sensitivity. This orange colored filter blocks the blue and blue-green portion of the visible spectrum up to approximately 500 nm. It reduces the excessive sensitivity of color infrared films for this spectral range, helps avoid a blue tint and differentiates colors more evenly. Filter factor depends upon the film's sensitivity.