Flash sync speed is the fastest shutter speed at which a camera can be used with an electronic flash without causing part of the image to be underexposed. Using a shutter speed faster than the sync speed can result in dark bands or partially exposed areas because the shutter may close before the flash has fully illuminated the scene.
Photographers can safely use shutter speeds below the flash sync speed to maintain proper exposure, while higher-end cameras and flash systems may offer high-speed sync options for faster shutter speeds. Understanding flash sync speed is essential for achieving correctly exposed images when combining flash with ambient light, especially in outdoor or high-speed photography situations.