The Metz Mecalux 11 is amongst the very best of purely optical slaves. Like all optical slaves, it triggers an auxiliary flash from a main unit without a directly wired connection. But the Mecalux 11 has a little more going for it. Many slaves only feature a flash shoe, but the Mecalux 11 can be used with a hot shoe connector or a standard PC cord. On the side of the unit there is a pc female socket, and on top there is a standard hot shoe connection.
Unlike most slaves which have both a hot shoe and a pc socket, the Mecalux 11 will simultaneously trigger flashes connected via its pc socket and its hot shoe-usually if one is enacted, the other is cancelled out. The Mecalux 11's hot shoe rotates 360°, and the bottom features a "cold" flash shoe as well as both 1/4"-20 and 3/8"-16 threaded female sockets.
Fastest compatible shutter speed of 1/300th second for focal plane shutter cameras