B & W offers three filters for infrared photography, each with its' own unique features. #092. This dark red filter is primarily for black and white infrared films. It filters out light below 650 nm. With color infrared film it produces pictures of a pure red image while making good use of the relatively low sensitivity of infrared films. Filter factor is approx. 20 - 40. #093. This black infrared filter will filter out the entire visible spectrum. It is used with black and white infrared films with a sensitivity up to 1000nm. Filter factor is determined by the film sensitivity. #099. This orange colored filter blocks the blue and blue-green portion of the visible spectrum up to 500 nm. It reduces the excessive sensitivity of color infrared films in this spectral range, separates colors more evenly thereby avoiding a blue tint. Filter factor depends upon the film's sensitivity.