An Art Form That's Precise

But Friendly Enough to Wink

By Matt Lake

 

You may not have heard the term before, but the chances are strong hat you've seen a lenticular image or two. In fact, it's almost impossible not to go past one without stopping cocking your head and swaying back and forth to get a better look. They've been stuck on cereal boxes, advertising awnings, department store displays, postcards and buttons- and even, in a very crude form on CD covers. And in every case they contain some kind of eye--catching animation or 3-D perspective.

Since these images don't need a special viewer to display their optical illusions, they are sometimes called auto animated and auto stereo images. Some go so far as to call animated 3-D images 4-D images because they add the dimension of time.

The most common misperception is that these pictures are holograms. They're not. While both types of technology can add depth to two-dimensional pictures and create animated effects, they look different, work differently and are used for different purposes. Holographic images are created by lasers, can be printed on very thin metallic or transparent sheets and typically display a rainbow sheen like the reflection on a puddle of oil.

Lenticular images are much thicker because they have a ribbed plastic surface, and they are generally clearer and brighter than holograms.

Lenticular images have been around since just after World War II, when developments in plastics made it possible to create the ribbed sheet that sits on top of every motion -image card and auto stereo image, these ribbed sheets are called lenses, or lenticular sheets, because they are actually dozens of optical-grade cylindrical lenses sitting in parallel lines on top of several specially prepared images. The lenses reflect the images beneath them so that as your point of view changes, the image you see changes- creating the illusion of movement.

The three-dimensional effect works on the same principle as view master stereoscopes: each eye sees its own version of the same scene, each taken from a slightly different angle - just as each eye sees something a little bit different when viewing something that is actually three dimensional - so the brain perceives the scene in three dimensions. On a lenticular sheet, each cylindrical lens refracts the different pictures to different eyes without the need for the viewer to look into a device.

From the outset, the lenticular technique was used for gee-whizz value. The company that pioneered the process in the 1940's, Variview, started by making animated political campaign badges with he slogan "I Like Ike!" and moved on to animated cards that were stuck on boxes of Cheerios. The techinuqe was apparently too successful - cards were so frequently ripped off he boxes that the company had to put them inside the boxes. Throughout the 1950's and 1960's, the lenticular process was used to produce sublime and ridiculous images, from flicker-image novelty rings and animated postcards of a winking girl to a 3-d devotional picture of Jesus.

In recent years,since Variview closed its doors, other commercial studios have continued the tradition. ... Depthography Inc. based in Manhattan, offers a large catalog of magnets and lenticular images designed to be hung on walls. It has developed window displays for Macy's and is working on a 45-panel animated display for a moving walkway at Kennedy airport.

While these projects are often generated from computer graphics, the lenticular process doesn't inherently rely upon microchips or computers. But Panasonic has recently released a computer printer with Windows software that prints animated sequences of images from computer files onto lenticular sheets the size of credit cards.

Precisely how lenticular images are prepared is a closely guarded secret. Variview did not patent the process because it's founder, Victor Anderson, didn't want to reveal his trade secrets. The original lenticular cameras expose images to photographic film through numerous lenses of a lenticular sheet, which creates an interleaved image that is ready to develop photographically and apply to lenticular sheets. Now a lot of lenticular images start life as three-dimensional computer models or flat digital photographs, which are processed by computer and printed on a commercial printer.

Not all lenticular images are created equal. The earliest examples were literally auto stereo images: two images that either gave a parallax perspective on the same image or switched between two images. Panasonic's motion -image printer takes six discrete images and prints them in strips beneath lenses.

But advertising-quality lenticular images cram dozens of frames on a single image. Beneath each lens in a Depthography image, for example, could be lines from 30 to 50 images. The lenses magnify each line; together, they form a full-size image. If the sight of a lenticular picture isn't enough to make you stop in wonder, the fact that it's made up of that many different images surely should be.

 

 

Card Deconstructed

If you draw a fingernail across the surface of a motion image card, you'll feel ridges in the plastic. These are actually rows of optical grade lenses that focus light on different strips of the surface at the back of the card and magnify whatever is there. When you look at the card from different angles - by moving the card or your head - you see different images, so the figure on the card seems to change or move.

Interleaving the Images

To make a lenticular image, as motion-image and autostereo cards are called, each image is divided into parallel strips (optically, by photographing it through a lenticular sheet, or mathematically, using software) and distorted so each strip is squashed thinner. The images are interleaved so one very thin strip of each image is printed next to a strip from the next. That requires very precise positioning, especially since most motion-image prints are color photographs that need to be printed in four separate color passes. The more sophisticated lenticular images can have dozens of images aligned beneath each lens. To make sure that these precisely printed images are precisely aligned with each lens, they are often printed in mirror image directly onto the back of the lens sheet.

 

ILLUSTRATION BY MIKA GRONDAHL

COPYRIGHT 1999. THLINKS TO DEPTHOGRAPHY'S SITE

 


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