About a dozen years ago, I engaged in the only cosmetic surgery of my life (so far!), LASIK. It corrected my far vision. But now that my aging crystalline lens is as impliable as a piece of beef jerky, I require reading glasses. And there’s not a thing Photoshop can do about it.
Photoshop is similarly incapable of correcting a photograph that was captured or digitized out of focus. Consider the following examples. In the first, the image is simulated to be out of focus using Photoshop’s powerful Lens Blur filter. In the second, I slather on a heaping helping of the Smart Sharpen filter with little evidence of positive transformation, not to mention lots of clipped highlights and shadows.
Compare that to the same image as it was actually captured by Jason Stitt of the Fotolia image library. With accurate focus at its disposal, the Smart Sharpen filter is capable of rendering tactile detail, even with a tiny Radius value (the number after the slash below).
The purpose, then, of Photoshop’s Sharpen filters is not to invent detail where none exists, but rather to enhance the detail that is already there. You can correct for source imperfections, call attention to facial features, enhance elements for effect, or add impact for output. And Photoshop supplies three filters to meet your needs: Unsharp Mask (the old-school approach), Smart Sharpen (great for detail-intensive images), and High Pass (best for portraits). Apply any one of them to a smart object, and you have the most flexible approach available to Photoshop.
I explain it all in this video how-to. Click the image below to open the video in another window: