When On is selected, the camera will time photographs to reduce banding, areas of under- or over-exposure, or (in photographs taken in continuous release modes) uneven coloration caused by the flicker of such light sources as fluorescent or mercury-vapor lamps (note that the frame rate may drop while flicker reduction is in effect, and that the frame rate may slow or become erratic during burst shooting).
“Flicker Reduction Shooting” in the Photo Shooting Menu
Flicker reduction can detect flicker at 100 and 120 Hz (associated respectively with AC power supplies of 50 and 60 Hz). Flicker may not be detected or the desired results may not be achieved with dark backgrounds, bright light sources, or decorative lighting displays and other non-standard lighting. Depending on the light source, there may be a slight delay before the shutter is released. The desired results may not be achieved if the frequency of the power supply changes during shooting.
Flicker detection will not take effect at shutter speeds slower than 1/100 s (including Bulb and Time) or when Continuous H (extended) is selected for release mode or silent photography, HDR, or exposure delay mode is enabled.