Problem : Solution Use a brush with the Unsharp Mask filter
Apply the Unsharp Mask filter
Open the image you wish to work with.
Choose Filter » Sharpen » Unsharp Mask.
Click twice on the plus sign just below the preview window in the Unsharp Mask dialog box to increase the magnification to 300 percent.
Set the options as necessary. For our example, working with the snowboarder image, we chose 161 for the Amount, 1.2 for the Radius, and 5 for the Threshold.
Click OK to apply your settings.
Take a picture
A snapshot is a temporary copy you can make of an image to preserve a particular state of its progress. Snapshots are stored in the History palette. To take a snapshot of your image in its currently sharpened state:
Click on the Open state in the History palette to step backward and remove the effects of the Unsharp Mask filter.
Paint from memory
The final step is to use the History Brush tool and the history state saved in your snapshot to apply the Unsharp Mask filter effect only to the necessary area. To do this:
Select the History Brush tool from the Toolbox.
Click on the down arrow next to the Brush thumbnail on the tool options bar to open the Brush Preset Picker.
Double-click on the Soft Round 100 pixels tip.
Choose Normal from the Mode dropdown list and set the Opacity to 100% and the Flow to 30%.
Set Snapshot 1 as the source for the History Brush tool by clicking in the box to its left in the History palette.
Click and drag the brush over your image. Every time you drag the brush over the area, the filter is reapplied; so you only need to do this once. Otherwise, you might over-sharpen the image. As shown in our Solution image, your snowboarder is now crystal clear and the background's diffused appearance remains intact.
Make a difference
As useful as the Sharpen filters are, sometimes too much of a good thing is just that—too much. Not every image calls for clean, crisp edges. And sometimes, only part of an image needs sharpening. Using the technique we've shown, you can now create subtle differences between the foreground and background areas in your images.