Front and Rear Curtain Synchronization
Some cameras offer the option of rear curtain synchronization (Rear mode) triggering the flash unit at the end of the exposure time. Rear curtain synchronization is particularly advantageous when using slow shutter speeds (slower than 1/30 sec.) or when shooting moving objects that have their own source of light. Rear curtain synchronization gives a more realistic impression of movement because the light streaks behind the light source instead of building up in front of it, as is the case when the flash is synchronized with the front shutter curtain. Depending on its operation mode, the camera uses shutter speeds slower than its sync speed.
For Type PEN flash: You could select the synchronization mode as either front curtain (
) or rear curtain ( 
) at the back of the flash. The flash will fire according to the mode selected to match with the camera shutter.
For Type CAN, NIK, OLY, PANA, SON flashes: The camera controls front or rear curtain synchronization, therefore no setting is required to be changed on the flash.
Note: The rear curtain synchronization is only possible on cameras with this feature. See your camera’s instruction manual for details.