Flickering when doubling shutter speed I have a Nikon D750 and cannot figure out the logic behind video (or still photos in live view) and flickering. I live in Norway, so the electricity is 50 Hz. If I shoot video at 1/50 or 1/100 second I get no flickering when using indoors (1080p 24 fps). However, if my shutter speed is increased to 1/200, 1/400 and so on I get flickering again. Does anyone know why this is happening? I also tried to record video at 1/200 and play back (to ensure that it is "real" flickering and not just an issue with the live view preview) and the issue persists. I though any multiplier of 50 should provide a flicker free video, but this appears to just be the case for 1/50 and 1/100 second. Does it have anything to do with the readout time of the sensor/rolling shutter somehow?
Sadly this isn't how it works.
It could work with 25FPS and 1/200 if the shutter is precisly on the light impulse.

Also keep in mind that even if the electricity is 50Hz, the light could have a refresh of 100Hz.
Or you were just lucky that the shutter allways was on the light impulse.

Solution:
Well, sadly you don't really have a direcr solution for this one. But youbhave two Options:
1. Buy yourself some Video Lights (Sometimes also normal lights have a label "Flicker free" those should work too)
2. Do not shoot with such high shutter speeds.
If you know 180° rule and just do it for artistic reasons, skip this part:

You should allways record with dpuble the shutter of your FPS: 25FPS=>1/50 50FPS=>1/100
This will give you the most natural look.
If you choose a higher Shutterspeed, the footage will kinda look robot-erisch and unnatural.
If you choose a lower shutterspeed, it will have more motion blur and feel almost dreamy.

But you may want to use this for artistic reasons, a slow shutter for a dream sequence or a faster shutter for sport video where you wsnt to see everything and stop the video.