A while ago Ian Homewood started using the High Pass method of sharpening because he was never satisfied with the results he achieved using Photoshop's USM. Here he explains how to use High Pass and why it's more controllable and less susceptible to sharpening artefacts than other methods.
Once you have finished editing your image and have resized it as required, the following steps will apply High Pass sharpening.
1) Make sure the background is editable
If you have created multiple layers, use Layer>Flatten Image to return to a single layer.
Double click the background layer, the following dialogue box will appear.
Give the layer whatever name you want, then okay it. This will save the layer and make it editable.
2) Create a layer for the high pass filter
Duplicate the existing layer by dragging it onto the create new layer icon
3) Applying the High Pass filter
From the menu bar, select Filter>Other>High Pass, the following dialogue will appear.
The radius you need to set will depend upon the size of the image and the type of detail. Finer details need a smaller radius to avoid becoming over sharpened. A good rule of thumb is to adjust it so the edge details are visible without being too well defined. Once you are satisfied with the setting, okay it.
4) Blend the layers
At this point, only the high pass layer is visible, to obtain the sharpening you need to change the blend options on this layer.
The blend mode I use most often is Soft Light, shown below.
Hard Light gives a much harsher effect, which is sometimes useful where there isn’t much detail in the shot.
5) Fine Tuning
To check the effect the sharpening layer is having on the image, hide it and then make it visible again. You should see a very slight overall lightening of the image and fine detail will become more distinct.
If, when you make the layer visible, too much sharpening appears, turn down the opacity or select a different blend mode. Soft Light is the most subtle.
NB For the purposes of this article I have deliberately used high settings, to emphasise the change.
Words and Pictures copyright Ian Homewood