3D glasses work by allowing our eyes to see what is known as an “anaglyph”. The anaglyph is an old technology, but it is still used online to view 3D photos and movies. Many 3D camcorders feature external software that converts new 3D video formats to anaglyph. An anaglyph can be viewed by anyone with any type of equipment—for example a flat-panel 2D television or video monitor—as long as the viewer has a pair of red and cyan (or other appropriate color) pair of glasses.
What is a 3D Anaglyph?
An anaglyph combines two specially separated images to create the illusion of 3D. The two images in an anaglyph slightly overlap one another in two
contrasting colors (usually red and cyan). In daily life two different perspectives are delivered to our brain via our right and left eyes. Our visual cortex interpolates the information into our 3D experience of the world.
With a 3D anaglyph (it can be a movie or a photo) The two different perspectives occur in the same frame using two separate colors (most often red and cyan). The goofy-looking glasses allow each of our eyes to see either the red or the cyan frames separately by blocking one color or the other. Our brain is ‘tricked’ into perceiving a three dimensional image where there is none. But fashionistas take note, you aren’t limited to red and cyan. There are also green and magenta or amber and blue pairings to suit your mood. Practically speaking, these alternatives have nothing to do with fashion. Instead, they deliver a sharper image with less color washout.
One final advantage is that colored glasses are cheap! If you don’t already own a pair (they are often included for free with a new 3D camcorder), I recommend purchasing them. You can find inexpensive sources (some for as little as one penny) by clicking here.
Cost saving tip: Cheap paper glasses tend to be better than the more expensive plastic pairs. This is because paper glasses use a gel medium that has a purer color than the molded plastic. Try both if you’d like; neither will break the bank. The one advantage to the plastic versions is that they can be more comfortable. Free 3D glasses can be obtained in their polarized variety if you ‘forget’ to return yours at the theater. I’m not aware of any sources for free anaglyph glasses.
Why are some glasses red & blue and some are dark?
3D glasses are tools that divide light. They collect light coming from one source and split that light so that it travels to your left and right eyes. As mentioned above, red and blue glasses take footage recorded as an anaglyph and divide it into its component parts (red for one eye, blue for the other). Your brain does the rest, creating the illusion of depth from the two differently colored images. Yet color is just one aspect of light.
When light is reflected off certain surfaces or filtered by specialized equipment it becomes polarized. Rather than vibrating equally, the light from polarized 3d images vibrates in one primary direction. Polarized glasses permit only one specific angle of light to enter through each lens. This conveys different perspectives to each eye.
If you still have trouble understanding the concept of polarization, envision a polarized lens filter on an SLR camera or even the polarized lenses of your sunglasses. Now picture a shallow goldfish-filled pond in a sunny park. Without a polarized lens or polarized sunglasses, there is glare off the pond and it’s difficult to see the fish swimming beneath (or they appear dull and blurry). Your polarized lenses allow you to cut through the glare and easily see the fish beneath the water. The polarization of the lenses cancels out the angle of light that reflects off the pond.
Remember though, polarized 3D glasses may look like sunglasses but they are not! I received an email asking about 3D sunglasses. You will harm your eyes if you wear regular 3D glasses in the sun – they do not filter out UV light.
To learn more about 3D video, check out my new book Shoot 3D Like a Pro: 3D Camcorder Tips, Tricks and Secrets