What are lenticular images, and why do they look so awesome?

What are lenticular images, and why do they look so awesome?

    Every day, there are hundreds—perhaps even thousands—of advertising messages knocking on your head trying to

gain access to the part of your brain that decides to buy things. With so much money at stake, it's hardly

surprising that advertisers go to such extraordinary lengths to catch our attention. The only trouble is, our

brains habituate: they quickly get used to seeing the same thing over and over again. So the advertisers have to

keep thinking of new tricks to stay one step ahead. One of their latest ideas is to print posters, magazines, and

book covers with lenticulars—images that seem to change as you move your head. Let's take a closer look at

how they work!

    Nothing! Lentils are tiny orange, green, or brown pulses popular with vegetarians and—no—they have nothing

to do with how book covers work. The connection between "lentil" and "lenticular" is simply a

matter of words. Lenticulars are so-called because they use lenses, which are pieces of plastic or glass that bend

(or "refract") light to make things look bigger or smaller. Lenses got their name because some of them

just happen to look a bit like lentils! You can find more in our main article on lenses (we even tell you how to

make a lens of your own, in about 5 seconds flat, from a drop of water).

    How do you make something like our book cover up above? You take your two different images and load them into

a computer graphics program. The program cuts each image into dozens of thin strips and weaves them together so

the strips from the first image alternate with the strips from the second. This process is called interlacing. If

you look at the doubled-up image printed this way, it's just a horribly confusing mess, but not for long!

Next, you place a transparent plastic layer on top of the doubled-up image. This is made of dozens of separate

thin, hemi-spherical lenses called lenticles. These refract (bend) the light passing through them so, whichever

side you're looking from, you see only half the printed strips. Move your head back and forth and the image

flips back and forth too like a kind of "visual see-saw".

    For all this to work properly, everything has to be printed with incredible precision. The lenticles have to

be exactly the same size as the printed strips underneath them and lined up with them exactly. Not only that, the

image has to be adjusted and printed so that it looks exactly right when viewed through a certain piece of

lenticular poster(with a certain "pitch"—or

number of lenticles per inch) at a certain viewing distance. (That's a fiddly technical process and I

won't go into the details here, but you can find out more in the articles and videos in the further reading

section below.)

    Nothing says lenticulars have to flip back and forth between just two images: some have as many as 20

different images or "frames" (as they're sometimes called, using the language of moviemaking). You

could have half a dozen different images designed to point in slightly different directions, so an advertising

poster slowly and subtly changes its message as you walk past! You can also use lenticulars to create amazing 3D

images similar to holograms.

    For a basic flip image that changes as you move your head, you need to arrange the lenticles so both eyes

always see the same image; as you move your head, both eyes then switch simultaneously to the other image. Adding

more images, it's possible to create a basic illusion of movement (a bit like a flip book) and a zooming

effect, so the image appears to get closer or further away as you move the

flip lenticular poster back and

forth. With a slightly different arrangement of lenticles, arranged vertically, we can send one image to one eye

and the alternate interleaved image to the other, giving the illusion of a three-dimensional picture.

    Lenticular images are the neato transforming pictures that often came on trading cards in the 1980s and 90s.

They were handy for freaking out young children or filing your nails. Turn them one way and they show one picture.

Turn them another and they show another. How? A trick of the light. And plastics.

    Lenticular images are the kind of things they used to give out as free promotional material. They were best

suited to things like trading cards of Transformers, because when looked at from one position, the card would

display an image of the untransformed robot, while from another angle, it would display the image of whatever it

transformed into. (On the back could be a description of why transformers transformed into cars with passenger

compartments even when there weren't people to be passengers on their world.) The cards were covered with a

piece of ridged plastic.

    The images take advantage of light's tendency to bend, and only bend a certain amount. The ridges of

plastic essentially 'block' parts of the image from the viewer. Light from certain parts of the image is

reflected or bent away from the viewer. Each ridge, across the page, directs certain slices of the image back to

the viewer. As the viewer moves, they are exposed to different parts of the ridges and see different slices of the

page.

    The image underneath the ridges is a series of interlaced slices - a little like a colored bar code. Each

slice matches up with a section of ridge, and the slices come together to make the full image. Early lenticular

images generally only had two pictures and flipped back and forth. More modern ones will be a little more

complicated, with many different images, each corresponding to a different segment on the ridge. Some will even

present a 3D picture, by showing slightly different image slices to each eye. For example the right eye could see

one angle of a face, and the left eye could see another. This is how the eyes regularly build 3D images in the

mind, and so the two images combine into a 3D picture. All it takes it the right kind of sectioning, and, of

course, plastic.

    This dialogue by Shakespeare very likely refers to 5D lenticular pictures — those accordion-pleated creations that show different images

when you look at them from the left or right. In Shakespeare’s time and in the 20th century, lenticulars were

manufactured as amusing distractions. Today, the technique is finding a home in fine art — including this month

at The Art League.

    One of the first examples of a lenticular picture

still in existence is the Double Portrait of King Frederik IV and Queen Louise of Mecklenburg-Güstow of Denmark by

Gaspar Antoine de Bois-Clair, signed 1692.

    As you can see in the photo, this type of 3D lenticular picture uses a corrugated structure to achieve the effect. Look at it from

the left, you see the king; from the right, the queen; and if you look at it straight ahead, you get a mish-mash

of both.

    Starting in the 1950s, companies like Vari-Vue were able to mass-produce lenticular images through lenticular

printing — a novelty you’re probably familiar with from Cracker Jack boxes and baseball cards:

    These flickering images are the result of the same principle but a different process: the images are behind a

small, ribbed plastic lens that shifts what’s in focus.

    Lenticulars as fine art

    Artists such as Roy Lichtenstein and especially Yaacov Agam have used lenticular design in their artwork.

    Photographer Sally Canzoneri began creating lenticular prints for a specific exhibit proposal: it was to be

displayed in NoMa, a DC neighborhood that was undergoing a lot of change. While considering how best to show that

change, Canzoneri happened to see this tutorial on creating lenticular images.

    It was a match.

    “I’ve found that people get drawn into them in a way they don’t get drawn into my flat pictures,”

Canzoneri said. The way viewers engage with the content “comes — at least in part — from the fact that the

viewing experience is broken up and blended in an unusual way.”

    It can also lead to happy accidents. In the print seen in the video at the top of this post, women’s marches

from 1913 and 2017 intersect. Because of the way the images overlap, when viewing the black-and-white image, you

can see a slight pink glow above the 1913 marchers’ heads.


    How it works

    Canzoneri’s prints use the old-fashioned accordion style, not the plastic lens. It’s a more hands-on

endeavor, and one that took some experimenting to refine.

    It starts, of course, with two images. Using Photoshop, Canzoneri stitches together strips from each image,

for a final product that looks like this when printed:Then, using a carpenter’s square, she carefully folds it

into the accordion shape. After a few tries, Canzoneri found the right type of paper to use and the correct fold

depth (about an inch).

    Double Takes

    Which brings us to “Double Takes” — Canzoneri’s exhibit of lenticular photographs on view now at The Art

League. You can catch these images through February 4, 2018.

    Bring your walking shoes — the better to interact with the artwork. And, Canzoneri says, she hopes the photos

encourage viewers to “go outside and look around with fresh eyes.”

    Have you ever walked past an exhibit graphic that seemed to move? Or maybe the image suddenly shifted? Your

eyes weren’t playing tricks on you … the graphic was playing a trick on your eyes.

    These types of graphics are known as lenticular prints.

    What Are Lenticular Prints?

    Today’s lenticulars aren’t the moving image stickers you used to get at the doctor’s office as a kid (or

adult—no judgment here). You know the ones: if you swiveled it a bit it looked like She-Ra was raising her sword,

or a transformer was … transforming. Well now that same concept makes things that do this:One of the advantages

of lenticulars is that visitors can get a nice pop of 3D or animation without needing any additional equipment. As

cool as everyone looks wearing those 3D glasses, it’s a bit of waste to supply those for one panel. Lenticular

prints simulate motion and/or dimension using specially fabricated two-dimensional prints.

    HOW DO THE 2D PRINTS MAKE IT LOOK 3D?

    It’s called stereoscopy. It’s a visual effect created by providing slightly offset views to both of your

eyes at the same time. When your brain mushes (technical term) the two visuals together, you see the combined

image with additional depth and volume. In other words, your brain takes Image 1 and Image 2 and turns into a much

more awesome optical illusion. To do that, the designer has to interlace the images.

    One of the advantages of lenticulars is that visitors can get a nice pop of 3D or animation without needing

any additional equipment. As cool as everyone looks wearing those 3D glasses, it’s a bit of waste to supply those

for one panel. Lenticular prints simulate motion and/or dimension using specially fabricated two-dimensional

prints.

    HOW DO THE 2D PRINTS MAKE IT LOOK 3D?

    It’s called stereoscopy. It’s a visual effect created by providing slightly offset views to both of your

eyes at the same time. When your brain mushes (technical term) the two visuals together, you see the combined

image with additional depth and volume. In other words, your brain takes Image 1 and Image 2 and turns into a much

more awesome optical illusion. To do that, the designer has to interlace the images.

    Other than they’re really fun? Lenticular prints add impact to displays of static photographs and other

images. They can also create a depth of content. By layering images on top of each other, a lenticular can show a

before and after, or a variety of images on a theme in a way that shows shifts. Recently, Smithsonian Libraries

worked with SIE to create lenticular prints for their exhibition Magnificent Obsessions: Why We Collect. Visitors

could see the image of a prized possession, and then it would shift, showing the collector. Visitors can see a

visual connection between the two images, and figure out that the stories behind those two images are intertwined.