The Chinon AF 50 mm f /1.7 is the first serial lens equipped with the the infrared autofocus system.
Autofocus operations start after pressing a big yellow button on the left side of the lens. Then, as is seen from the scheme, an infrared Light Emitting Diode (E) is turning in the direction of a receiving sensor (S) until it receives the beams reflected back from the object (O).
Since the emitter and the lens are linked mechanically, the angle of deviation is in accord with the focusing distance. Successful focusing is indicated with the green LED and audible signal.
Infrared beams are well absorbed by any dark object and and reflected by a light-colored one, that's why the attempts to take a photo of a person in black suit with a white stone as a background may confuse the focusing system.
Posted by: nukemall Date of publication: 06.03.2011