Aaton - 25fps - 180 degree shutter - in doubt about whether light sources will flicker

Stephen Perera · May 2

....so there I was happy as a clam as they say and I was shooting my Aaton with Vision3 500T 16mm film inside in a room that was lit with a couple of overhead LED tube lights.....plus one light that I brought along.....so day two of shooting and the person I'm shooting tells me......when I record video with the mobile the light flickers, no problem with your camera right........so I went blank and carried on......but with that doubt in my mind hahahah.......I know MY light won't show flicker......but the two overheads????? we're in Europe obviously.....

Can anyone share wisdom on this with me without any of the deep science......

Simon Wyss · May 2

The shutter of your camera must be in synch with the pulsating light. Therefore you use a synchronous motor run off the same grid sector as the lamps or a crystal controlled motor plus a phase shifting unit. You can also observe the light in the reflex viewfinder, it should be at a minimum while adjusting the motor. Then the maximum happens during exposure. No need of adjusting anything with LEDs on DC or well smoothed-out AC.

Stephen Perera · May 2

thanks for the reply but far too technical for me im afraid.....hahaha....I dont see any flicker when I look through the viewfinder of my Aaton...I don't use a monitor....plus I cant adjust anything on the Aaton either.....it's 25fps at 180 degree shutter and thats it.....it's a modern LED light strip on the ceiling and overhead thats im asking about.....

Simon Wyss · May 2

You were asking something technical, so you mustn’t abhor the answer. It is not as simple as it's 25fps at 180 degree shutter and thats it. Is the motor crystal controlled or by some electronics (which is not my field at all)?

You won’t see flicker but slow increase and decrease of light intensity. I think it’s called interference pumping.

Stephen Perera · May 3

I never abhorred the answer merely stated I am not technical in understanding what you described. Thank you for taking the time to answer I appreciate it very much.

Uli Meyer · May 5

I shot film footage before in a similar situation and it flickered.

Simon Wyss · May 5

It is a technical topic. A crystal controlled motor runs very steadily, an LED array on grid follows the mains frequency which varies all day long. Or it is electronically controlled but you don’t know to what frequency. Finally, the phases should be in coincidence so that you have the most light on film. It’s perhaps 50,006 Hz and 49,979 Hz one against the other, something like that. As I’m typing this, the grid frequency is 50,026 Hz here. https://www.swissgrid.ch/de/home/operation/grid-data/current-data.html