I was checking if my smart TV presented PWM using my smartphone's camera in super slow-mo. When doing so I could see the screen flashing very rapidly. After changing some settings in the TV, the flashing became more of a black bar moving super slowly horizontally, but it was so slow that the entire black bar blocked the view of what was being displayed like for 5 seconds.
The question is if flashing very rapidly means a higher PWM frequency that a slow thick black bar that moves horizontally but takes a lot of time to scroll through the screen.