How 3D Movies Work With Digital Technology

Films Like "Avatar" Feature Three Dimensions With Clear Images

Oct 4, 2009 Adam Pracht

The classic, but disorienting red and blue 3D movies appear quaint compared to today's standards. Here's an overview of modern polarization technology in films.

Three dimensional movies are crawling their way out of the history books as a 1950s fad and becoming a popular option for movie studios and theaters.

A short list of some of the movies released in 3D in 2009 alone reveals this trend:

Coraline
Monsters vs. Aliens
Up
Ice Age 3: Dawn of the Dinosaurs
G-Force
Final Destination: Death Trip 3D
Cloudy with a Chance of Meatballs
Toy Story and Toy Story 2
A Christmas Carol
Planet 51
Avatar

In particular, "Avatar" has exploded in popularity since its December 2009 release, becoming the second-highest grossing movie of all time with more than $1 billion in ticket sales. "Avatar" is now second only to James Cameron's other blockbuster, "Titanic."

As of March 2008, Patrick Corcoran of the National Association of Theater owners told the associated press that 2,385 theaters have 3D capability. According to the association, in 2008 there were 5,786 theaters in the United States.

A number of reasons may explain this trend:

Greater competition with high-quality home theater options, driving desire for a unique big-screen experience.
The willingness of customers to pay more for a 3D movie ticket, covering the greater cost of production.
Success and audience turnout for modern 3D films. Many point to 2004's "Polar Express" as the start of this trend, where just 66 IMAX theaters with 3D accounted for 25 percent of the film's returns.
Better 3D quality with polarization technology.
Cheaper production and equipment with digital movie technology.
Improved technology to transform 2D films into 3D features.

Binocular Vision and 3D Movies (Biological Basis for Why 3D Movies Work)

Most people see out of two eyes. This is a basic fact of humanity, but it's what makes possible the illusion of depth that 3D movies create. The eyes in a human are spaced about two inches apart, meaning that each eye gives the brain a slightly different perspective on the same object. The brain then uses this variance to quickly determine an object's distance.

To test this, simply hold a hand or other object out a few feet. Alternate closing one eye and then the other. The object will appear to move against the background.

3D movies take advantage of this fact. Two images filmed (or animated) at slightly different perspectives are projected on a screen. Using a variety of technologies, 3D movies permit each eye to see only one of them. The brain combines the separate images as if it were looking at an actual object, creating the illusion of depth.

Classic Red and Blue 3D Movies

The concept behind 3D movies is nearly as old as motion pictures themselves, dating back to the early 1900s. However, the first record of a paying audience for a 3D movie was "The Power of Love", at the Ambassador Hotel Theater in Los Angeles on September 27, 1922.

The film used "anaglyph" format, which created a 3D effect by projecting images in two different colors. Special glasses with color filters would allow each eye to see only the opposite color on the screen, and produce the illusion of depth.

This was the technique used during the later 3D movie craze during the 1950s. This method has a number of drawbacks, however. It doesn't allow natural coloration. The dual projectors for the two images limited the amount of film, meaning most films required an intermission and that any repairs had to ensure the two strips remained perfectly in sync. Also, for many people it created disorientation and headaches. The popularity of the format did not extend much beyond the 1950s.

Modern Polarization 3D Movies

Modern 3D movies use a different technique to separate the images. Light is composed of waves, but normally these waves are oriented in random directions.

In linear polarization 3D movies, all of the light waves for one eye are aligned vertically and for the other eye are aligned horizontally. The glasses are also polarized so that one lens only allows in one direction of polarization.

Imagine a wavy sheet of metal being fed through two rollers. It passes through smoothly if it is aligned with the rollers, but is completely blocked if one tries to feed it through at a 90 degree angle. This is similar to how the polarization technique works.

The drawback of linear polarization is that tilting one's head allows light from the opposite projection to leak through. Circular polarization avoids this pitfall.

Other 3D methods

Other methods for 3D movies include eclipse, which quickly alternates left and right images on the screen and blacks out the other eye with either a mechanical shutter or LCD darkening glasses. These systems are expensive for common use.

Interference filter technology creates a very clear 3D color image. One image uses very specific wavelengths of red, green and blue (the constituent colors of light) and the other image uses slightly different wavelengths of red, green and blue. Special glasses filter out those specific wavelengths to make two images. The drawback is the glasses are expensive in comparison with polarization techniques.

The copyright of the article How 3D Movies Work With Digital Technology in Film/TV Industry is owned by Adam Pracht. Permission to republish How 3D Movies Work With Digital Technology in print or online must be granted by the author in writing.

Red and Blue 3D Glasses for Anaglyph Format