What is maximum flash sync speed? What does it really mean? When and why it is important for flash photography? To answer all these questions, let’s start by looking at the basic camera component related to flash photography.
The shutter
Most SLR cameras have a focal plane shutter. It consists of two shutter curtains (typically called 1st/2nd or front/rear curtain). When the shutter release button is pressed, one curtain will travel across the sensor and the second blade follows the first one after a period of time. Depending on the exposure time, there may or may not be a moment when the entire sensor area is fully exposed to the light. At short exposure time, a slit formed by the two shutter curtains will travel across the sensor, exposing the sensor by scanning through it. By reducing the slit width, the shutter can effectively produce a shorter exposure time otherwise impossible due to the limit of the mechanical shutter movement. The image below illustrate the shutter operations at long (top row) and short (bottom row) exposures.
