A method of focusing where focusing distances are set automatically. In 35mm SLRs, a passive phase detection system that compares contrast and edge of subjects within the confines of the autofocus brackets in the viewfinder and automatically sets focusing distance on the lens. Autofocusing motors may be in the camera body or the lens itself. Active IR (infrared) autofocusing systems may also be in 35mm SLRs in the form of beams in dedicated autofocus flash units, or, in a few models, built into the camera itself. Commonly found in amateur lens/shutter cameras. These beams are emitted from the camera or flash, bounce off the subject, then return and set focusing range.