Two stage release button halfway pressing for auto focus Complete pressing takes the picture Lock the button for long exposures or continuous shooting Prevents the camera from shaking Compatibility: Nikon D7200 D5500 D3300 Df P7800 D5300 D7100 D610 D5200 P7700 D3200 D600 D5100 D3100 D7000 D5000 D90 D750