Invented in 1931, a strobe light is a light that flashes repeatedly at a set rate. In photographic work, most strobe lights use a flash tube powered by a capacitor; the capacitor is discharged in response to a power from a trigger transformer. In stage lighting, strobes work directly off of AC power. Typically, a stroble light flash is around 200 microseconds long and may occur as fast as hundreds of times a second.
A strobe light will seem to stop or freeze repetitive motions, to create slow-motion effects, and to create other special lighting effects. The “stop motion” visual effect is used for many applications, including tuning guitar and bass strings.
In certain cases, a strobe light may trigger an epilptic seizure. The speed of the strobe seems to be the defining factor in these cases. At 10 flashes per second, 65% of sensitive people may be triggered. At 5 flashes per second, only 5% of sensitive people may be affected. Even for those without photosensitive epilepsy, more than 30 seconds of continuous strobe lighting effects can cause disorientation.