Amount determines how much to increase the contrast of pixels. Typically 20 – 30%
Radius is used to identify how many pixels around edges to sharpen. Typically 40 -70
Threshold determines how far pixels must be from surrounding area in order to be considered an edge. Anything greater than 0 is useless.
Amount = 20 (also try 25 & 30)
Radius = 50
Threshold = 0