DESC: Electronic Flash EF-500 DG SUPER is designed to work with both AF 35mm SLR and Digital SLR cameras of popular manufacturers, for advanced flash photography. It has a maximum guide number of 165 in feet or 50 in meter at 105mm focal length (ISO 100). The projection angle of the flashlight is set automatically to match the lens’ focal length ranging from 28mm wide-angle to 105mm medium-telephoto. It also incorporates a built-in diffuser that expands the angle of illumination down to that of 17mm lens.