Noise Reduction Bound
Sets the threshold for noise reduction.
Valid values are in the range
100. If no value is supplied, the default is
nr value sets the threshold at which noise is removed. 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.