The concept of morphing involves creating smooth transitions between two different images. The smoother the change, the more convincing the effect. The artist works to establish common points between images that do not move and aligns the images on those points. For a man-to-werewolf morph, for example, the artist places the man's eyes, nose and mouth in the same locations as those of the werewolf. These common points stabilize the transition, reducing horizontal or vertical jitters that spoil the illusion of change.
With a cartoon animation, the artist has control over the images because he draws all of them. If he wants a morph effect in a scene, he draws the "before" and "after" images and determines how much time the transition will take. Film movies use 24 still frames of images for each second of action, so a two-second morph needs 48 images. The first frame begins as the before image. The artist then draws 46 transitional images, each one looking progressively more like the final one. The after image becomes the 48th in the series. Though this involves a great deal of hand labor, it is no more laborious than producing two seconds of any other scene in the animated feature, since the artist already creates it all by hand. To cut down on the amount of work, an artist now uses a computer to automatically generate the transitional frames.
The 20th century saw many new techniques developed to create dramatic special effects for film. Technicians were limited to what they could do with lenses, light and photographic effects for most of that period. Early attempts at morphing, such as in the 1941 movie "The Wolf Man" and "The Mummy" film of 1932, used a technique called the lap dissolve. An actor sat or stood in a certain position, and the crew shot a foot of film, then stopped the camera. A makeup artist worked on the actor, adding a few features. The actor would then assume the same position as before and the crew would shoot another foot of film. They repeated this process until they completed the entire transition scene. Movies and video continued to use the lap dissolve until computer image processing offered a better alternative in the 1980s.
A computer program can automatically produce the in-between images needed to make a convincing morph scene. Each image consists of thousands of tiny dots called pixels, each having a certain brightness and color. The artist uses the program to identify the "before" and "after" images and the key points to align the images. The software examines each pixel and creates a series of gradually blended images, resulting in the "after" shot. A modern computer and software generate a morph in a few seconds or less. Because the technique is quick, the artist can gradually refine the key points and details, repeating the morph process several times until he or she is satisfied.