When you get up in the morning
and the light is hurt your head
The first thing you do when you get up out of bed
Is hit that streets a-runnin’ and try to beat the masses
And go get yourself some cheap sunglasses
Oh yeah, oh yeah, oh yeah

Cheap Sunglasses by ZZ Top

Fancier 3D Red/Blue Glasses

A few days ago I blogged about man-eating lions of Tsavo, and the film Bwana Devil based on their exploits. The interesting thing about Bwana Devil is that it was a 3D film shot using anaglyphic technology. That's a fancy way of saying if you wore special glasses with red/blue filter you could see a three-dimensional movie. Anyway, I thought the technology needed an explanation since it is so widespread yet nobody every thinks about how it works.

Audience Watching Bwana Devil

3D Glasses Used for Bwana Devil

The word "sterographic" has its root in the Greek "stereo" or "solid". There are two techniques for making stereoscopic images: stereograms, which have two separate images, one for each eye, and anaglyphs, which combine the two separate images into one image using different colors for the left and right images and with special glasses to ensure that each eye only sees the appropriate image (left or right).

But why does all this work? Simple. Because our eyes are about 2.5 inches apart they receive separate, but similar, scenes. In normal viewing, our brain to construct a 3D image by using the eyes as two separate cameras. The slight difference in viewing angle allows the hardware in the brain to extrapolate where the edges are in three-space. Wow — that was a really lousy explanation. Let's try it again.

The red lens over the left eye masks out the right channel in red (colored filters remove all light of that color), so the left eye only sees the background image and the blue image superimposed on it. Similarly, the blue lens over the right eye masks out the right channel in blue (just as with red, blue removes all light of that color), so the right eye only sees the background image and the red image superimposed on top of it. The background image is the same; the only difference are slightly shifted left and right highlights. Here's a more technical discussion.

What is an anaglyph?

Anaglyphic stereograms (anaglyphs) are stereo pairs of images in which each image is shown using a different color. The two images are overlapped and then viewed using red/green or red/blue glasses (depending on the colors used). This means that the color channel is used for the stereo separation and therefore the perception of anaglyphs is monochrome (black and white), although color anaglyphs can be made.

The word anaglyph comes from the Greek anagluphos, meaning "wrought in low relief"; this comes from the word anagluphein, which means "to carve in relief" (ana = up + gluphein = to carve).

Who invented the anaglyph?

The discovery of anaglyphic 3D came in the 1850s as the result of experiments by the Frenchmen Joseph D’Almeida and Louis Du Hauron. In 1858 D’Almeida projected 3D magic lantern slide shows in which color separation took place using red and blue filters, and the audience wore red and blue goggles. Louis Du Hauron created the first printed anaglyphs using early color printing and photography techniques.

Anaglyphs FAQ

Viewing anaglyphs requires special glasses. Printed images, as opposed to those on computer monitors, can be viewed through colored lenses. These are the cardboard glasses familiar to anyone who's been to a 3D movie or seen 3D comics. The largest supplier of glasses seems to be American Paper Optics in Bartlett, TN; it claims to have shipped over 500,000,000 — that's five hundred million folks — 3D glasses. That's enough for just about everyone in America and Europe to have a pair. Hang on just a minute. ... Yup. I have one of them in my collection of detritus. How about that. Anyway, American Paper Optics will send you a free pair of 3D anaglyphic (red/cyan) glasses if you ask. (Details at the end of this entry.)

Tight Rope Walkers in the Air
Free Entertainment on the "Zone", 1915

This is far from being a new technique:

In 1915 the city of San Francisco invited the world to celebrate the opening of the Panama Canal with a world's fair, known as the Panama Pacific International Exposition. The occasion was also a celebration of the city's recovery from the 1906 earthquake and fire. The Exploratorium is housed in the last remnant of the Exposition, the Palace of Fine Arts. Without the media of today, its promoters had to find other ways to publicize the event. Thanks to the Keystone Company, people all over the world were able to experience a day at the fair by looking at the stereograph pictures through special viewers that created the 3-D effect.

Panama Pacific International Exposition in 3D

Anaglyph of Mars Odyssey Orbiter

Ok, so much for how it works and the history of it. In the days of videogames and DVDs does anyone care about cheezy 3D effects using colored glasses? Surprisingly, the answer is a resounding yes. There are a number of anaglphys on the JPL Mars and the European Space Agency Websites. Many microscopists use anaglyphs to give depth to otherwise flat scenes, enhancing the ability to spot interesting features. You can even get a version of the first-person shooter game Quake with anaglyphic functionality.

Sand Dunes of Nili Patera Taken By Mars Lander

Oh, and bet you thought I forgot about the free 3D glasses offer. Well, I didn't. For your totally free 3D glasses follow these instructions:

Order one free sample of anaglyphic (red/cyan) glasses by sending an unsealed SASE (Self Addressed Stamped Envelope) with $0.37 postage to address at the bottom of this page

American Paper Optics, Inc.
3080 Bartlett Corporate Drive
Bartlett, TN 38133

American Paper Optics

Sources and Further Reading

1. 3D Photograph (photos and tutorials)
2. Yahoo Groups: Anaglyph
3. Anaglyph Stereo Quake (first-person shooter game)
4. Panama Pacific International Exposition in 3D
5. Sand Dunes of Nili Patera Taken By Mars Lander
6. Anaglyphs from JPL Mars Mission
7. Anaglyph of Mars Odyssey Orbiter
8. Anaglyphs from European Space Agency