#Front Curtain Sync
Front Curtain Sync is the default sync mode used with flashes by most cameras. The shutter opens and closes for a length of time determined by the shutter speed set. The shutter consists of a front and rear curtain. Front Curtain Sync is when the flash is fired at the beginning of an exposure, or at the front curtain. If the exposure is long enough to show motion after the flash, the motion is shown differently than in Rear Curtain Sync. Picture a person walking in a dimly lit scene (so that a long exposure can be used) from camera left to camera right. If they start walking at the left of the frame and the camera is fired in Front Curtain Sync mode, their image will be frozen at their starting place on the left and any motion will appear as a trail in front of them.