The ef 610 dg st is multifunctional shoe mount type flash featuring a powerful guide number of 61 and designed to work with the most popular digital slr cameras this flash unit provides fully automatic flash photography for digital slrs with automatic ttl exposure control it combines a convenient array of functions with ease of handling and includes an autozoom head that automatically sets the optimum illumination angle between 24 mm and 105 mm as well as offering bounce and swivel capabili