I noticed something strange when I used my PAL camcorder with my Macbook 15 in the background. The keyboard was flickering in the viewfinder - but not when I looked with my own eyes.
I have seen this before, when I was in Europe with my US camcorder recording at 30fps (60 fields per sec) it wouldn't sync with the fluorescent lights which flicker at 100Hz - twice the cycles of the main power US=60Hz EU=50Hz. The flicker I saw in my trip to Italy footage was caused by the 60 fields per second (two fields = one frame) not syncing with the 50Hz of the lighting.
But here int he US I acquired a PAL camcorder with uses 25fps (50 fields per sec) and for some reason the keyboard appears to be operating at 60Hz.
Why? If I took it to Europe and plugged it in would the keyboard run at 50Hz? I would think it operated on DC since that's what the AC adapter does - converts AC to DC for the machine to run on, but for whatever reason that's not the case.

Obviously there's nothing wrong - I'm just curious how this works.