With a powerful guide number of 200' at ISO 100 and 105mm, the?Sigma EF-610 DG ST Flash?works with Canon E-TTL / E-TTL II and offers users the ability to illuminate the subject or scene both on camera and off. The unit also has a zoom range of 24-105mm with full frame cameras and has a wide-angle panel that will extend this to 17mm. The head will tilt from -7 to 90? and rotate right 90? and left 180? for full bounce capabilities. And, it has wireless master and slave TTL functionality.