If flash is a brief burst of light, why does a Speedlite have a high-speed sync setting to freeze action?
Rich Moales, Tenbury Wells
BRIAN SAYS… Unfortunately, the terminology is causing confusion here. A typical Speedlite flash at low power levels is a very brief pulse of light, lasting less than 1/1000 sec, which freezes the movement of a subject. The flash fires during the period when both shutter curtains are completely open.
High-speed sync mode causes the flash to emit light for a longer duration, so that it can be used with shutter speeds faster than the camera’s sync speed. Portrait photographers often like to use wide apertures to separate a subject from the background, which regularly requires a corresponding fast shutter speed
