Sharpness is a combination of two factors: resolution and acutance. Resolution is straightforward and not subjective. It’s just the size, in pixels, of the image file. All other factors equal, the higher the resolution of the image the more pixels it has the sharper it can be. Acutance is a little more complicated. It’s a subjective measure of the contrast at an edge. There’s no unit for acutance you either think an edge has contrast or think it doesn’t. Edges that have more contrast appear to have a more defined edge to the human visual system.
There are three main reasons to sharpen your image: to overcome blurring introduced by camera equipment, to draw attention to certain areas and to increase legibility.RAW files from any modern camera are always slightly unsharp. Every step of the image capturing process introduces blur. As the light passes through the lens elements—no matter how well made—some definition is lost. When the sensor processes the photons falling on it, the sharpest transitions are averaged out and slightly blurred. When the three different color channels are interpolated to create the final image, again, a small amount of blur is introduced. Second, human eyes are attracted to contrast. When we look at a photo, we are drawn to the sharpest details. If you’re trying to direct a viewer, selective sharpening is one of the best ways to do it.
Finally, sharpening an image makes it easier to see important details. Text becomes easier to read, individual leaves stand out and faces in a crowd become more distinct.
You should about one thing about sharpening…
Sharpening: every photographer knows they should be doing it to their images but very few understand how it works and why it’s important.
lets see how sharpen a picture by photoshop cc