When any shutter speed is manually selected, the shutter's operation and control do not require battery power. The user can release the shutter without batteries, but the camera's built-in exposure meter will not work. It also expands exposure control, which is particularly useful when shooting with high-speed film. Shutter speed can be selected from 1 sec. In A mode, shutter speed is controlled from 8 sec.
Bulb exposure is also possible.
The FM3 A 's fast flash sync speed provides a broad range of control to let you shoot from dim to bright scenes with fill-flash. The FM3 A features automatic TTL flash exposure control. When the sensor determines that the necessary level of flash light has reached the film, it signals the Nikon Speedlight to turn off. A TTL flash-compensation button on the FM3 A lets the user slightly reduce the Nikon Speedlight's flash output. This feature can be used to achieve a balanced fill effect or to avoid over-exposure associated with shooting a subject in backlight or one standing against distant background.