Typically, it matters in 2 areas that mostly have to do with 50 Hz vs 60 Hz:
- Maximum frame rate is usually 25 for 50 Hz, 30 for 60 Hz. This may change as firmware evolves, but that's the way it is on my current cams.
- Anti-flicker for use with fluorescents or LEDs. You get light/dark banding in the images if you use the wrong mode. This isn't an issue with incandescent lights.
I've got some Dahuas that are easy to find PAL firmware for, but not NTSC, so I'm tempted to try it out just to see.