Sharpening is necessary with digital cameras to offset the small
amount of blurring that occurs because of the color filter
array. Actually, sharpening doesn't sharpen anything. What it
does is increase local contrast (particularly along edges). The
human eye interprets that increased contrast as sharpness.
Conventional wisdom holds that sharpening should be one of the
last steps performed on an image. This is so because other
process steps can decrease the sharpness of the image. If an
image is sharpened and then edited, the sharpening may be
decreased during the editing. Also, since sharpening adds a
certain amount of image degradation, it is not a good idea to
sharpen multiple times (there are exceptions to this, but you
have to know what you are doing; the exceptions will not be
dealt with in this article). This is not a problem for raw. Raw
files are not sharpened in the camera. As a result, it is up to
the photographer to determine the best point at which to sharpen
the file (e.g., in the raw converter