You can use the tonal range
sliders by choosing Very Low Key Image, Low Key Image,
Middle
Key Image, High Key Image or Very High Key Image according
to the key of the image that you are editing. Else choose Rank1 ...
Rank 5 that will be applied all over the same.
Rank 1 is the same as the
common Min Max replacement filter. It removes spurious
isolated noise
pixels.
Rank 2 is slightly stronger
than 1st Rank but sill preserves edges.
Rank 3 affects to the edges
slightly but removes a lot of noise.
Rank 4 is almost as strong
as a Median Filter, but does not do as much damage.
Rank 5 replaces with median
of the neighbors. It flattens noise nearly as much as a Median Filter
(at radious 1) but preserves edges better, since it only replaces out of
rank pixels where median just applies the median everywhere.
All Adjusted selections enables
the tonal range sliders. They allow to specify different ranking based
on the average RGB value in the 3x3 (less the center pixel) convolution
matrix.