Graphics programs can be used to both sharpen and blur images in a variety of ways. Portraits often appear more appealing when softened, especially the background in order to make the subject stand out more. This is an example of shallow depth of field and can be achieved with a camera by using a large aperture, or artificially within software, by selecting the background portion of an image, and then blurring it. The red-eye effect, occurring when flash photos are taken and the pupil is too widely open (thus reflecting back the color of the blood-rich retina), can also be eliminated. Edge enhancement is an extremely common method used to make images appear sharper, although many discourage this believing the end result is less natural-looking.