B+W is a German optics company owned by Jos. Schneider Optische Werke GmbH. Basically, it's an interference filter that reflects and separates the InfraRed and UltraViolet light from the visible spectrum for purer transmittance of the visible light spectrum... 88% of UV waves are cut at 380 nanometers along with 95% of IR waves at 700 nanometers, helping to ensure that light hitting a camera sensor is limited to the visible spectrum. When used along with variable ND filters while recording with a digital sensor, potential infrared colour shifts are prevented and colour accuracy is preserved throughout the frame. Cameras converted to Full-Spectrum can still be used for regular colour photography with this filter. Please look at my other ads for more photo gear and call or text 780 554-7193 to arrange a convenient pickup time from my home.