This is probably something for the tech guys here?



There is a discussion in a Swedish forum about ”why are LED lights flickering on film, when they look OK for the human eye and brain, live?” The basic reason could be poor rectifying drivers, i.e. a LED is not powered by ”pure” DC. The human brain doesn’t catch the flickering, however the camera does.

The short solution is to adjust the setting on the camera according to your region’s electric power system:

E.g. USA = 60 Hz AC -> set camera to NTSC or 30 or 60 fps.
E.g. Europe = 50 Hz AC -> set camera to PAL or 25 or 50 fps.

However, as a digital train is not powered by a sinus wave AC, but with a ”square wave DC” with different frequences for receiving ”1” or ”0”, i.e. 8.3 kHz and 5 kHz respectively:

Why does it seems as if my camera setting of 25 fps - as I’m in Sweden - also prevents train LEDs from flickering on film?