Although Photoshop does have a Sharpen filter, better results can be obtained using the High Pass filter, and you have the control over how much or how little you sharpen your image. In this quick tip I will show you how to sharpen all or some of your image.
Image from sxc.hu
Open the image and duplicate the background layer.
Change the layer mode to Overlay – this will increase the contrast greatly, but that will be corrected in the next step.
With the High Pass settings window open, make sure you have the Preview box checked so you can see the results.
It depends on the size of your image, the amount of sharpening required and the final effect required as to how much or how little you apply with the slider.
For this image, at full size you will get a good result applying 2.0 pixels, but if you reduce the size as I have to 580px wide, you will need to apply around 4.0 pixels.
You can also apply a layer mask to your High Pass layer so that you sharpen selectively. In the image below, the houses and flowers in the foreground were quite sharp enough, so I used the High Pass filter, added a layer mask and masked out everything except the sea and mountains in the background.
I hope this quick tip helps you with your photography post-processing for your future projects.