The FM2 is a mechanically-controlled manual focus SLR with manual exposure control. It is operable without batteries and only needs the two S76 or A76 batteries, or one 1/3N battery to power the light meter, which consisted of an internal 60/40 percent centerweighted system linked to a center-the-LED exposure control system. The exposure control system used vertically arranged +/o/– light emitting diodes (LEDs) on the right side of the viewfinder to indicate the readings of the meter versus actual camera settings. This metering system can be traced back to the Nikkormat FT (aka Nikomat FT) of 1965 and its center-the-needle system. The viewfinder also had Nikon’s standard interchangeable focus screen with various focusing options.