(Minor updates to this article were made in February 2019.)

Sharpening is a very important step for optimizing digital photograph files. If you let your camera save images in the common .jpg format (a compressed image format that is often used on the web) the camera is applying sharpening to the image produced by the camera sensor. If you use the raw format (a high quality format that retains the original sensor data of the exposure) you will find that the photograph looks soft until you apply sharpening during the post production phase.

Sharpening optimizes the visibility of details that are already in your photograph. It is a matter of more clearly revealing what is in the photograph than  a matter of creating detail where there was none. Most sharpening works by increasing the contrast between light and dark areas in the image — what we call sharpening as actually more about adjusting the relative brightness of adjacent portions of the photograph.

The image above is an example of a small section of a photograph.[1] It is a “100% magnification crop” of a tiny area from a much larger photograph made with a high megapixel DSLR camera. A “100% magnification crop” is an image displayed so that each pixel — or individual picture element — of the original photograph is displayed using a single pixel on the screen. (Things are a bit more complicated than that when using modern high-resolution monitors, though I’ll let that description stand for now.) 100% magnification crops let us look very closely at what is going on in photographas “at the pixel level.” In this case, the full original image from which these small examples were extracted would be equivalent to prints at a width of roughly 10-12 feet.

The right side of the example shows this tiny section of the photograph before sharpening. The left side shows the results of fairly typical sharpening. Continue reading Sharpening Basics: A Primer →