So first, it is important to remember that the original image needs to be in decent focus. If you have an image that is in poor focus it would be near impossible to save it.
But of course we don't always get that in perfect focus image when we take the shot, so here a couple ways to sharpen your images.
Now when we sharpen images all we are really doing is increasing contrast across pixels. Well at least that is a simple way to put it.
To sharpen an image using the unsharp mask is pretty simple. All you have to do is select the layer you want to sharpen. By the way, it is a good idea to work with a copy of the layer you are wanting to sharpen so that anything you do can be undone if necessary.
To apply the unsharp mask select: filter - sharpen - unsharp mask
Once the unsharp mask is selected use the sliders to play until the desired effect is achieved. And there you go... you have a sharpened image!!!
But what if I don't like the noise that has been added to the rest of the photo?
What if I only wanted to sharpen certain areas of the photos?
What if there was an endless supply of ice cream? .... sorry distracted ....
So if you want to apply selective sharpening to an image it is very simple. Follow the normal steps to sharpen the image, and then apply a layer mask to the layer that has the effect. From there you simply paint with white to reveal the effect in the area that you want to be sharp. And done...