Irregular Webcomic! #692

The middle panel shows an image processing effect known as edge enhancement, while the last panel uses an effect called edge detection. Most graphics software has filters that do these operations. Slight levels of edge enhancement (less obvious than what I used in the middle panel) can often make a photographic image look "sharper" and superficially more pleasing to the eye. If you look closely however, you can see the sort of artificial effects introduced around the edges of objects (as seen here quite obviously). So to people who know about it, edge enhancement is often considered a distraction rather than an improvement.

This is important for modern digital images, such as those found on DVDs. Some production studios apply edge enhancement to the film frames, believing that the audience will prefer a sharper image. On good quality home theatre equipment, this effect can often be seen and can be an annoying distraction from the film viewing experience. If you ever see a DVD image that looks "unreal" or "too sharp to be true", particularly where there is a sharp edge between foreground characters and background scenery, then you will see why edge enhancement is not always a good thing.

2014-01-14 Rerun commentary: Lest you come away form this comic thinking that edge enhancement is always a bad thing, it isn't. Applied judiciously, it can sharpen the appearance of photos and video without causing perceptible artefacts. Furthermore, it has uses beyond conventional photography and video.

Medical images in particular are routinely sharpened, to make small details stand out more for diagnostic purposes. You want your pathologist to have the best possible chance of spotting tumours and other nasty things in your CT scans and MRIs and x-rays - and edge enhancement is one of the tools they use.

And the other processing method mentioned here, edge detection, has numerous important uses in computer vision and image processing. It's often a first step in analysing an image to look for objects in the scene, which has applications in all sorts of fields, from film production to surveillance to robotics and navigation.