Optimized Rear Curtain Sync
We’ve added Optimized Rear Curtain Sync capabilities with the ability for you to set the shutter speed at which rear curtain sync is engaged. To access this setting, plug your transmitting ControlTL radio into the Utility and click the Flash tab. Use the drop down menu to choose when you would like rear curtain sync to begin, then check the "Optimized Rear Curtain Sync / Manual Shutter Speeds" box. Please see the Wiki page for more details.
We found in testing that the Canon system rear curtain sync timing is actually not at the precise end of the shutter opening, but actually slightly before (Fig 1). We have been able to improve on this timing to put the flash at the very end of the exposure (Fig 2).
|Fig 1: Rear Curtain Sync using Canon's technology. Note: streak below golf ball. Camera: 7D; Shutter Speed: 1/10th; Aperture: f/5.6; Lens: EF 50mm f/2.5 Macro|
|Fig 2: Rear Curtain Sync using PocketWizard's technology. Camera: 7D; Shutter Speed: 1/10th; Aperture: f/5.6; Lens: EF 50mm f/2.5 Macro|
You do not need to set anything on your flashes including Canon’s own Second-Curtain Sync button. Toggling the setting on the flash will not change the setting in the radio.