Haloless Sharpening Tutorial
By Mathias Vejerslev

I was writing this up for a friend somewhere else, and thought I might as well post it here for those that are not aware.

Advanced Layer Blending in Photoshop can be used for a great many things. Amongst those are halo less sharpening. I think I became aware of ALB about two years ago, and I have used it since in many different techniques.

Here´s how to reduce halos when sharpening (its a quick example, mind you):

The lower of the three is unsharpened. I duplicated that layer, and obscenely oversharpened with USM (middle).

Then I right-clicked that layer, and set the blending options like this:

Which resulted in what you see on top (still a little too sharp, but you can simply reduce the opacity of the layer to taste).

You do this by Alt-dragging the triangle sliders to create a semi-transparent blend of the extreme whites and extreme blacks, in order to emphasize the midtones of the current layer. You can quickly determine how far you must go by simply dragging the endpoints to where the annoying halos dissappear, then split the endpoint to this position to blend it.

You can use this technique with other layer based sharpening techniques such as High Pass sharpening and others with great effect, as you can sharpen much more without visible halos.

This is a variation dubbed midtone sharpening.

Enjoy

Mathias