The fastest shutter speed at which a camera with a focal plane shutter can use normal flash. On many cameras it is about 1/160 to 1/250 second.
At faster speeds the shutter curtains never open the whole frame at once, so part of the image would be dark. High-speed sync works around this. See also flash synchronization.
Martin Kaninsky
Martin is the creator of About Photography Blog. With over 15 years of experience as a practicing photographer, Martin’s approach focuses on photography as an art form, emphasizing the stories behind the images rather than concentrating on gear.