Select On to reduce noise (bright spots, randomly-spaced bright pixels, or fog). Noise reduction takes effect at all ISO sensitivities, but is most noticeable at higher values. The time required for processing at shutter speeds slower than about 1 s roughly doubles; during processing, “l m” will flash in the viewfinder and photographs cannot be taken. Noise reduction will not be performed if the camera is turned off before processing is complete.
If Off is selected, noise reduction will only be performed as required; the amount of noise reduction is less than that performed when On is selected.