Lenticular printing

Ever see one of those plastic cards with an image that changes when you tilt the card? That, my friend, was an example of lenticular printing.

How it works

A lenticular printed card has two components - the source images, and a ridged plastic covering which is actually made of many long, very thin (approx 0.3mm) lenses called lenticules. The source images are split into strips and arranged such that each lenticule covers several strips, one strip from each of the various images. A cross section would look like this:

/\/\/\/\/\
OXOXOXOXOX

O  = First source image
X  = Second source image
/\ = Lenticule ridge

Thus, depending on the angle that the card is viewed at, one or other image is visible. This example shows only two images but more can be used. However, the more images there are, the more they tend to blur into each other. A usual amount is somewhere between three and twelve.

Lenticular printing can be used to create two different effects - depth or motion.

Depth

If the lenticules run vertically on the image, a primitive 3D effect can be created, by using source images that are pictures of the same object from different angles. Each eye sees the card at a slightly different angle and thus the lenticular printing effect can send the appropriately different source picture to the eye.

Compared to a hologram, a lenticular image is less impressively three dimensional, and presents a blurrier image. On the other hand, it can be in full colour, whereas holograms are usually monochromatic, and it can be seen in almost any lighting conditions, whereas holograms need to be precisely lit.

Motion

If the desired effect is to create the illusion of motion when the card is tilted, it is better to have the lenticules arranged horizontally. Otherwise the same effect which is useful for 3D will damage the movement effect as each eye sees a different frame of the animation.

Uses

Lenticular printing is used almost exclusively as an attention-grabbing gimmick. The eye is drawn to motion, or to mysteriously three-dimensional objects on flat cards, so it's very effective. As a result you tend to see lenticular printing used in advertising, or even directly on products, particularly those aimed at children such as breakfast cereals or comics. It can be used for decorative purposes too, and advanced techniques even allow for lenticular printing onto fabric such as T-shirts.

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I'd like to thank amnesiac for goading me into writing this by insulting me repeatedly in the chatterbox.

Sources:

• How Stuff Works - http://entertainment.howstuffworks.com/question607.htm
• World Holographics - http://www.world3d.com/faqs.html

But wait, don't answer!

There is an application of lenticular printing that is not merely an eye-catching gimmick. A company called UrbanMapping produces a map called a DynaMap that layers three different views of Manhattan onto one surface:

1. Street Level (yellowish background with blue and black streets)
2. Subway system (blue background with subway colors matching the lines)
3. Neighborhood (shades of reddish-oranges)

Want to know the nearest subway entrance? Find yourself on the street map and tilt it. Your eyes are in the same place and can easily scan for subway stations, uncluttered by other map elements. Want to know where the Chelsea district is? Tilt it a little further, and the streets/subways vanish, showing only the neighborhoods and landmarks.

You can even bend or tip the map just so to slighty blend the images, so you can see exactly where on Broadway the G line stops, for example.

I've got one of them. It's beautifully executed, easy to use, and a brilliant use of an old analog technology.

It's also elegantly restrained. Modern lenticular technology can cram as much as 100 images into a single space. This works great for video-like displays, but trying to isolate a single image requires great precision in the viewing angle. DynaMap picked its three layers and stuck with them. They are now planning a series called PanaMap that will include San Francisco, Washington DC, Chicago and Boston.

It hints at a new style of layered, analog information/interaction design, in which information is related spatially, but distributed in time, in a low-cost, no-power (in use), hi-res medium.

I can't mention DynaMap without telling the sad part of the DynaMap story. It was designed by Ian White in 2001. Despite his good idea, earnest efforts, and 3 years of time and money investment, he was a lone designer against the shifty business world. Big Publishers are now stealing the idea and are in the process of producing knockoffs without compensating him for the use of his intellectual property. He hasn't the resources to fight. You can read a little about his frustrating journey at Core 77, URL below.
http://www.core77.com/reactor/11.03_ian_white.asp

You can also patronize the site at www.urbanmapping.com