nrs Noise Reduction Sharpen
Determines the amount of sharpening in pixels above the bound set by
nr, reducing noise in the image.
Valid values are in the range
100. If no value is supplied, the default is
Pixels with a luminance value that falls below the threshold are considered noise and will be blurred. Pixels above the threshold will be sharpened according to the
nrs parameter value.
nr is set, then
nrs will be set to its default, and vice versa. If neither value is supplied, then no noise reduction will be applied. Try setting
nrs=40 below to see the difference from the defaults.