The Rollei Bay 70 Infrared Blocking Filter from Heliopan block the infrared spectrum below 780nm. It is designed for use with black and white and color films that are sensitive to certain values of infrared light not visible to the human eye. Using traditional contrast filters such as a yellow 12, red 25 or green 15 will produce a color shift which may not be desired in the final image. Greens may become blue, red becomes green and yellow becomes blue/green and infrared becomes red.