For years there have been novelty cards that display one image when held at one angle and another image when tilted slightly. The principle behind these cards, called lenticular photography, was first demonstrated by Gabriel Lippman in 1908. (Lippman also developed a color photo process for which he was awarded the Nobel Prize for Physics in 1908). Depending on how the underlying photographs are taken, lenticular images can convey the illusion of 3D and/or video motion. You may have seen them on CD jewel cases, movie posters, Pok�mon cards, souvenirs and novelty items.

With a digital camera it's possible for you to create lenticular images yourself or have them made for you at a reasonable price.

How it Works

A lenticular image has two components; a printed image and a lenticular lens screen through which the image is viewed. There are three simple steps from beginning to end.

1. Capturing the images. Since a lenticular image displays one image after another as you change your angle of view, it creates animations much like an old fashioned flipbook. For this reason, each image is called a flip. The more flips you use the more complicated planning and preparation become. For two flips, the process is quite straightforward. The basic rule is that the images must be the same size but they don't even have to be related. As you increase the number of flips the more movie-like the animation becomes. The number of images you can use is partly dependent on the size of the image. Smaller images can have more flips because the angle of view changes little from one side to the other. On larger images, when the angle of view varies a lot across the face of the image, the strips must be wider to prevent "ghosting" when you can see more than one strip. It's said that smaller images can contain 3⁶ or more flips or frames, about 1 second of full-motion video.

2. Interlacing the images. The interlacing software takes the selected images and cuts them into very narrow strips. It then interlaces these strips like a perfectly shuffled deck of cards. If two flips are being created, the first band is a strip from image 1, the second from image 2, the third from image 1, and so on. The software then saves the interlaced image in a file ready for printing.

3. Printing and mounting the images. The interlaced image can be printed on any high quality printer. The print is on or later mounted behind the lenticular lens screen—a sheet of plastic on which a series of cylindrical lenses are molded in parallel rib-like rows. Each or the lenses, called a lenticule, has a focal length equal to the thickness of the clear plastic sheet on which it is molded. Each lenticule magnifies a very narrow strip of the image placed behind it. If you change your angle of view, the strip that is being magnified also changes.

Taking Images

The way images are captured determines what form the final lenticular image will take. Here are some of the possibilities:

• Flip images are any two images that flip back and forth as you turn the lenticular image.
• 3D images are created by shooting the same object or scene from different angles much like a stereo pair. One way to do this is to attach your camera to a slider bar mounted on a tripod. Between shots, you keep the camera facing the same way but move it along the slider from left to right. When the images are interlaced, you'll seem to peer around the object as you turn the card.
• Video effects are created by shooting a sequence of images from the same position much like object photography of a still object, or a moving subject captured with a camera's continuous mode. For example, you can easily use your camera's continuous mode to capture the frames needed for a short video to be displayed on one of these cards. Alternatively, you can create a morphing effect and use those frames.