Digital sharpening produces its affects by accentuating contrast, both of texture and of contour. The accentuation of contrast along contours is produced by creating both a dark line and a light halo. While the filters used to sharpen images, such as Unsharp Mask or High Pass, don’t offer independent control of the light and dark components of a contour, you can control them separately using layers. It will take two layers to separate halo from line; one for the halo and one for the line. Filter the two layers differently to produce different thicknesses (Radius) and intensities (Amount) of halos/lines. Then, you can use the Blend If sliders of layers to specifically target either high or low values by moving either the shadows (black triangle) or highlights (white triangle) sliders of This Layer, making those values no longer visible. Some people like to set the Opacity of these two layers to 50% before filtration, so that they can conveniently readjust the intensity of the affect, moving the opacity slider up to make it stronger or down to make it weaker. If you do this too, remember that only the filter’s Radius setting can adjust the thickness of the contours it produces.