As you probably know, the standard way of sharpening an image in Adobe Photoshop is to use the Unsharp Mask filter. (I have always loved the fact that you use the unsharp filter to sharpen things.) There is, however, an alternative sharpening method that allows a lot of versatility even after you have run the filter. Here is how it works.

Make a copy of the image by putting it on to a duplicate layer. Set the duplicate layer’s blending mode to overlay, and then run the high pass filter. It can be found under Filter|Other|High Pass. Adjust the slider to control the strength of the effect. Press ok to accept. That is it! But, now you have even more possibilities.

You can decrease the amount of the effect by reducing the opacity of the layer. You can also limit the effect to certain areas by adding a layer mask. Painting the layer mask with white reveals the full effect, painting with black removes the effect, and painting with 50% gray will decrease the effect by 50%. This way you can vary the effect of the filter in different parts of the image.