Stereograms 10% Art, 90% Magic

By Gary W. Priester

I first became interested-no, make that obsessed-with stereograms in the mid-90s when the Magic Eye books and posters were all the rage. Stereograms are images that at first appear to be just a random pattern, but when you view them correctly, a 3D image appears. At the time I discovered these magical images, an article appeared in Publish Magazine explaining how these images were made. The author lived in the San Francisco Bay area as I did. I contacted him and said I would pay for a few hours of his time if he would show me how the images were made. He agreed. It was one of the best investments I have ever made. The author knew only enough to write the article and create a few very simple stereograms, but his sparse knowledge was just enough to launch my career.

Soon I was creating my own 3D stereogram images. I designed a website to display my creations. A Japanese publisher who was launching a stereogram magazine saw my images and asked me to contribute. I have been one of two contributors for nine years. The TJ MOOK series is up to issue 16 and the series has sold over four million copies. My co-contributor and I have co-authored two books of stereograms. We like to think that we have significantly raised the bar since the old Magic Eye days.

How Stereograms Work

A classic hidden image stereogram is created from two images: a “depth image” that the stereogram software uses to build the hidden image, and a repeating wallpaper-like pattern. The pattern repeats several times, the amount of repeats varies but is usually more than five times. The stereogram software makes subtle shifts in the pattern in each panel that are not apparent to the viewer. When the stereogram image is viewed correctly, the brain picks up these subtle shifts that occur from panel to panel and concocts the 3D image. The art is creating a panel with a random pattern to conceal the pattern shifts. Shifts in the wrong pattern will stand out like a hog on a sofa, so a good random pattern is essential.

The depth image is a grayscale image with 255 shades of gray that the software uses to determine depth. The same type of depth image is also used when creating a 3D model in a 3D modeling program. White comes forward the most, while black represents the most distant part of the image. There are also the remaining shades of gray that represent the layers of depth in between.

Most stereogram artists use a 3D modeling program to create their depth images. I have never gotten on that well with 3D modeling applications, so I create my own images in a vector drawing program. The drawing process is very different from conventional drawing. For example, if you were going to draw a ball, you would start with a circle. Then you would add some shading and maybe a highlight, a shadow too. These are all visual cues that the ball is round.

But when you draw a sphere for a depth image, you don’t have the luxury of a shadow or highlights or other visual cues. You construct the ball from the back to the front using shades of gray. In essence, you slice the sphere into many individual slices with a subtle change of value with each slice. This is the basic concept for creating all depth images.

The stereogram creation software uses these layers to compute the depth of the hidden image. Objects that are further away from the viewer are spaced farther apart. Objects that are closer to the viewer are spaced closer together. These modifications are made to each repeating panel. Your eye and your brain see these shifts in the pattern and together create the illusion of depth.

You don’t need special software to create a 3D effect however. You can do it with simple spacing. Objects should be evenly spaced, but each row of objects can be spaced closer together or further apart to create the illusion of depth when viewed as a stereogram.

How to Look at a Stereogram

People frequently tell me that they have never been able to see stereograms. They explain how hard they try. They just never have been able to see the hidden images. Some people even imply that the whole thing is a hoax, that there is no hidden image and people who claim to see the hidden images are just faking it. The only legitimate excuse I heard was from a person who only had one eye!

Most people who cannot see a stereogram are just not looking at the image correctly. Here’s what I mean. When we read or look at a photograph, our eyes, slightly crossed, focus directly on the page. This is perfect for reading or viewing a picture, but totally wrong for viewing a stereogram. When you look at a stereogram, your eyes are actually focused behind the image. Instead of your eyes being slightly crossed, your eyes are both looking straight ahead. You are using your near distance vision and not your reading vision. This type of viewing is counter to our normal instincts, so I suspect the primary cause for not being able to view a stereogram, is the viewer is focusing on the page.

Here is a simple technique that works for most stereogram-challenged persons. Get real close to the image so your nose is almost touching it. Let your eyes go blurry. At this distance they will blur anyway. Now, very slowly move away from the image, or move the image away from you while trying not to focus on the image. Relax your eyes and try to focus behind the image. Do this very slowly and with any luck you should start to get some feeling of depth. The important thing is to relax your eyes and to not try too hard. It is not a contest after all. Do this several times if at first you don’t succeed. The feeling of magic you get when you first see the image is well worth the effort. And for what it’s worth, after you have seen your first magical image, the next one will be easier to see.

For more information on how stereograms work and to see more images, visit http://www.custom-sterograms.com

To see more stereogram images visit my Stereogram Gallery at Graphics.com and the http://www.eyetricks.com/3dstereo.htm My books: Eye Tricks – Incredible 3D Stereograms, Arcturus Publishing, London, and Hidden Treasures 3D Stereograms, Sterling Publishing, New York are available from most on-line book sellers. Our third book, EYE BALL is still looking for a publisher.

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You probably did this when you were a child. Place your index fingers together, then looking straight ahead, slowly pull your fingers apart. As you do this, a floating sausage like shape will appear. This is the same viewing method you use when viewing a stereogram.

When you read a book or look at a magazine, your eyes are slightly crossed and focused on the page. When you view a stereogram, your vision is parallel and your focus is behind the image. As with the floating sausage created when you draw your fingers apart, your eyes and brain create an extra image, which creates the illusion of 3D depth.

A random pattern is best for disguising the subtle and not so subtle shifts the software makes to each panel. The stereogram with the very orderly pattern of plusses graphically illustrates the shifts in the repeating pattern. When designing a stereogram, I try for a complex random pattern, such as the stones, in which the pattern shifts are not as obvious. Both hidden images are the same 3D sphere.

Compass A combination of three types of stereograms: hidden image, floating image (the compasses), and mapped texture (the white outlines).

Coins A combination of hidden image and mapped texture stereograms.

Abert Entity A custom stereogram created for a new advertising agency. The floating logos on the top of the image are the agency’s actual logo, which also represents the hidden image. This is a combination of floating, mapped texture, and hidden image stereograms.