Certain light sources, including mercury vapour and fluorescent lighting, cycle on and off at the same frequency as the alternating current that powers them (50 Hz or 60 Hz). The flicker generated by these light sources appears as horizontal banding in live view and in movies during recording and playback. These horizontal bands usually seem to drift upwards a long distance, making movies appear to flicker.

Selecting "50 Hz" or "60 Hz" for this option in the "Live view" menu in the shooting menu reduces flicker caused by this phenomenon. If the users know the frequency of the alternating current, they can select the appropriate option. The recommended course of action if they do not know the frequency is to select either option, take a test shot, and view the results. This option does not reduce flicker not caused by alternating current.