« on: December 17, 2012, 11:40:20 PM »
Mt. Spokane, it's 60Hz. (That's the frequency.) 120 is the voltage. So the shutter must stay below 1/60. Impossible to do so the effect must be dealt with in post.
Here's a great write up on the issue...
While the power line frequency in the US is 60 Hz, the blink rate IS 120 Hz.
The definition of one cycle is when the voltage starts from zero, goes to a peak, then back through zero to a peak in the opposite direction and then back to zero. Thus the light starts at off, goes to a maximum, goes off again, then goes to another maximum (then back to off, but that last off is the start of the next cycle). Hence the light blinks twice per cycle.
Incandescent lamps don't blink badly because the filament doesn't have time to cool sufficiently between peaks, while fluorescents and discharge lamps do have time to cut off.
LED's (the future) may or may not blink depending on the power supply they have. LED's run on DC (which shouldn't blink), but some of the power supplies are simply AC rectified (all the humps are on one side of zero), which on average looks like DC, but which to a fast acting LED is (again) 120 peaks per second.
At 1/60 shutter speed you should get you a full exposure. 1/125 could get you 1/2 of what you want, if the capture takes place around the zero crossing.