This is the 52 mm Infrared and UV Blocking Filter (38) from Heliopan. It cuts UV below 300nm and infrared above 800nm. It is designed for use with black and white and color films that are sensitive to certain values of infrared and UV 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.
CMOS and CCD sensors and chips are very sensitive to infrared and UV light because of the coatings on these surfaces. Even if your camera has a built-in IR filter, there can be noticeable color shifts or incorrect exposures due to any number of factors. However, Heliopan provides specific filters that completely block infrared and UV rays resulting in more precise color control. In order to achieve correct exposure, testing is strongly recommended since infrared contamination can vary depending on time of day and the conditions under which you are shooting. In the black and white mode you can see the proper exposure in the camera display. In the color mode you can see it in the histogram display. This applies especially for the red channel.
