One of the flash features often lost when going wireless is the ability to sync the flash at the end of a (longish) exposure. Second curtain sync is very useful to give the correct sense of direction to moving subjects when photographed with a combination of a long shutter speed and flash.
The Canon wireless system disables the 2nd curtain flash synchronization feature when the flash is set to either master or slave. Other wireless triggering systems such as Pocket Wizards or Elinchrom Skyports can’t sync on the 2nd curtain neither when used on Canon bodies.
The fact is that, on the Canon system, there’s a direct connection needed between the camera and flash to trigger the later a split of a second before the shutter curtain closes and the exposure is ended.
A workaround for this limitation can be found on the latest 580EX II. The newest EX Speedlite (finally!) features a PC socket to allow it to work with external trigger systems. One classical way to trigger flashes is an optical trigger, sothat one flash triggers the others in an light-speed chain reaction.
The trick to achieve wireless second curtain sync is to use a flash on camera that will signal others with its flash burst at the right moment. Using an optical trigger on the 580EX II will allow it to sync with the timing of the on-camera flash, participating in the second curtain synchronized flash exposure.
I used an optical trigger from FlashZebra connected to the 580EX II threaded PC socket. This flash is set to Manual and a power level is selected to match the desired exposure of the subject. One piece of advice is to set this flash to slave mode. Although not strictly necessary from a functional perspective, setting the flash to slave mode will keep it from entering into battery save mode and ready for the action.
The trick to make all this work is to set the camera-mounted flash to “wired” (not master or slave) and in Manual power mode. If the camera-mounted flash is left on E-TTL mode, its pre-flash will prematurely trigger the slave flash, causing an incorrect calculation of the exposure and the slave might be still recycling when its time for firing comes with the 2nd curtain closing.
The power setting for the on-camera flash will depend of the effect desired. If (almost) no exposure contribution is desired from the on-camera flash, set it to the minumum possible (1/128), otherwise use the power setting needed for the subject and effect intended.
… and for the best effect, choose a dark background and some continuous light source on the subject.
-Gerard.
Thanks Gerard! You had helped me solved this rear curtain problem without the need to buy an expensive pocketwizard gadget. Thanks again!