As a photographic property, sharpness has been given new meaning by digital imaging software. Programs such as Adobe Photoshop offer an extraordinary degree of control -- after the fact -- over the apparent sharpness of an image. Photoshop has always offered a choice of built-in sharpening tools, all found in the Filter > Sharpen submenu. Until Photoshop CS2, the best choice (confusing name aside) has been Unsharp Masking. Unsharp Masking is a powerful tool, but thanks to new algorithms and expanded controls, CS2's new Smart Sharpen filter produces even better results. Smart Sharpen is slower than Unsharp Masking, but it offers far greater control -- and for my images, quality trumps speed. Now I find myself using Unsharp Masking only when I'm pressed for time.
In imaging programs, sharpening involves an edge-detection process: Wherever the software finds an edge, it exaggerates it by making the darker side of the edge even darker and the lighter side even lighter. The Smart Sharpen filter allows you to specify how much lightening and darkening you want. Once you find a setting with which you're particularly happy, you can click a button to save it for reuse on other images. This speeds up your workflow.
There are two modes in the Smart Sharpen interface, Basic and Advanced. Advanced mode incorporates all the choices and settings in Basic but adds the ability to lessen or eliminate the dark or light halos often caused by overzealous sharpening. Here's a rundown of the options available in each mode.