Sigma EF 500 DG Super Electronic Flash for Pentax Mounts Includes S-TTL flash photography for Pentax Incorporates modeling flash mode for proper light distribution to check the shadow of a subject Multi pulse flash enables reduced power setting from 1/4 to 1/128 in 6 steps -- pulse frequency can be set from 1Hz to 199Hz Light Projection Angle is automatically set to match the lens between 28mm and 105mm Also covers 17mm wide angle when the built-in diffuser is deployed