Tungsten fixtures in the range of 1000 W and below can show pulsing light. Typically this is not visible with the human eye, and it is also hard to see in the viewfinder, but it can result in visible flickering effects on the recorded footage when shooting with high frame rates. Depending on shutter/exposure time, this may be true for frame rates above around 100fps. Tungsten fixtures of larger size do not show this effect, as the light pulsing is more sluggish here.