The Metz MZ 54-4i and 58 AF-1 / 58 AF-2, the Sigma EF-530 DG Super and EF-610 DG Super, and the Promaster 7500EDF can produce multiple visible flashes per exposure to produce a multiple-stop-motion effect in one image. These multiple flashes must be at lower than full power.
The Metz flashes can fire up to 50 flashes at speeds ranging from 1hz to 50hz at a maximum of ¼ power. The Sigma EF-530 DG Super can fire up to 90 flashes at a frequency from 1hz to 100hz, with the limits changing depending on the power level selected (again, at maximum ¼ power). And Sigma EF-610 DG Super can fire 100 flashes as rapidly as 199hz, although that peak is only reached when power is decreased to ¹⁄₁₂₈th.
The Promaster 7500EDF can fire up to 10 flashes at seven choices of frequency ranging from 1hz to 100hz, at ¹⁄₁₆ power only.