High Speed Sync Flash
Understanding High Speed Sync Flash and Shutter Curtains
Before we can talk about high-speed synchronization (sync), we need to discuss what flash sync is. Flash sync is the computer-controlled feature in which the flash and the shutter release are synchronized such that the flash light output illuminates the subject for the specific moments that the shutter exposes the image sensor. The flash instantaneously lights up the subject (it does travel at the speed of light), so the flash doesn't last nearly as long as the shutter remains open even though this is very fast (1/60s, 1/125s 1/250s, etc.). There is a limit to the shutter speed, and this is the camera’s native sync.