An infrared (IR) filter blocks visible light, permitting only wavelengths in the infrared spectrum to enter your camera. These filters allow you to capture unique images that look entirely different than visible light photos. A typical infrared filter has a cut-off wavelength of 720 nanometers, which is just beyond the visible part of the electromagnetic spectrum.
While infrared photography is something I absolutely enjoy, I don’t use filters on my regular cameras. That’s because all digital cameras have an IR-blocking filter covering their sensor to prevent artifacts such as sensor-bloom (early digital cameras were prone to this problem). As a result, if you put an infrared filter on a normal digital camera, you’ll need to use ridiculously long exposures even at high-ISOs to capture an image.
One place where infrared filters are useful, however, is when paired with a full-spectrum or super-color converted digital camera (590nm or less). These filters allow you to use different cut-off wavelengths to get a variety of looks from a single camera.
Verdict: Useful with certain infrared-converted cameras but difficult to use with standard digital cameras.