The Fujifilm EF42 Shoe Mount Flash for Finepix HS-20 and X100 Cameras is a lightweight, portable on-camera flash with a 138' (42 m) guide number @ ISO 100. It has auto zoom that automatically matches the focal length of the lens (24-105 mm in 35 mm format), and can be set for APS-C or full-frame 35 mm use. Light output is adjustable from full power all the way down to 1/64 power. Exposure compensation of +/-1.5 EV in 1/2-stop steps helps you further refine your lighting. The flash head rotates 90° vertically, 180° to the left, and 120° to the right for total flexibility in directing your light. The EF42 is intended for use with the Finepix HS-20 and Finepix X100 cameras. It operates on 4x alkaline or 4x NiMH AA batteries. Batteries are not included.