To focus using autofocus with manual override (M/A): Slide the lens focus-mode switch to M/A. If desired, autofocus can be over-ridden by rotating the lens focus ring while the shutter-release button is pressed halfway (or, if the camera is equipped with an AF-ON button, while the AF-ON button is pressed). To refocus using autofocus, press the shutter-release button halfway or press the AF-ON button again. The fast maximum aperture of f/1.8 performs brilliantly under any lighting conditions and delivers beautiful, natural background blur that brings out the best in any subject. Compatible Format(s) - FX, DX, FX in DX Crop Mode, 35mm Film.