Edge Enhancement - Effects of Edge Enhancement

Effects of Edge Enhancement

Unlike some forms of image sharpening, edge enhancement does not enhance subtle detail which may appear in more uniform areas of the image, such as texture or grain which appears in flat or smooth areas of the image. The benefit to this is that imperfections in the image reproduction, such as grain or noise, or imperfections in the subject, such as natural imperfections on a person's skin, are not made more obvious by the process. A drawback to this is that the image may begin to look less natural, because the apparent sharpness of the overall image has increased but the level of detail in flat, smooth areas has not.

As with other forms of image sharpening, edge enhancement is only capable of improving the perceived sharpness or acutance of an image. The enhancement is not completely reversible, and as such some detail in the image is lost as a result of filtering. Further sharpening operations on the resulting image compound the loss of detail, leading to artifacts such as ringing. An example of this can be seen when an image that has already had edge enhancement applied, such as the picture on a DVD video, has further edge enhancement applied by the DVD player it is played on, and possibly also by the television it is displayed on. Essentially, the first edge enhancement filter creates new edges on either side of the existing edges, which are then further enhanced.