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. Optimized Rear Curtain Sync requires a MiniTT1 or FlexTT5 as the transmitter, but you can use any PocketWizard as a receiver. You will need to plug your radio into the PocketWizard Utility to activate this feature. The default setting is set to "off". You can adjust the setting to choose where Rear Curtain Sync will engage in the PocketWizard Utility under the Flash Tab. You will also need to check the "Optimized Rear Curtain Sync/Manual Shutter Speeds" box directly below.
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).
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.
Rear Curtain Sync in the Nikon system is simply controlled by the on-camera setting. When using a ControlTL capable radio, this setting is respected for enabling and disabling Rear Curtain Sync. With a Nikon camera, the Rear Curtain Sync setting can be left enabled at any shutter speed.
However, the Rear Curtain Sync functionality actually begins at 1/125th, and is used at all slower shutter speeds when enabled.
Refer to your camera's manual for more information.
8 Second Limit
When using a MiniTT1 or FlexTT5 radio, the longest supported Rear Curtain Sync shutter speed is 8 seconds. Rear Curtain Sync exposures longer than this will not sync properly.
Rear Curtain Sync and Bulb
Rear Curtain Sync and Bulb mode cannot be used together, because Bulb exposures are terminated manually by the photographer. With rear curtain sync, the radio sends a signal to the flash to fire just before the shutter closes. In Bulb mode, the exposure timing is infinitely variable, and the radios do not receive commands indicating that an exposure is about to end.