"With film images, sharpness is generally determined by the quality of our equipment and the film in use - so long as we hold the camera steady. Almost always the post-processing in lab or darkroom is aimed at retaining the sharpness we managed to get on film, though occasionally we may use some diffusion for effect. With digital images - and this applies to some extent to scanned film images - we have other considerations and far greater possibilities for sharpening after the event. In general this is not a way to make up for our deficiencies in taking the images (although it can sometimes help) but more concerned with getting the most out of our digital images."This article explains the different types of sharpening as well as looks at some of the tools and options for sharpening, including native Photoshop and two plugins, PhotoKit Sharpener and FocalBlade. Definitely worth a read.