The Difference between 3D Stereograms and Anaglyphs

The two sub-media are competing ways of creating 3D illusions.  Moviegoers are more familiar with the anaglyph technique.  Anaglyph 3D encodes each eye’s image using filters of opposite colors (red/blue; magenta/green, etc.). The two differently filtered images ensure different light information hits each eye, tricking your typical perception and causing the foreground to jump out at you (see below).  Stereograms make you do the work yourself, as you are about to see.

Stereograms

The term “stereogram” has become more generic.  But it used to be exclusive to this technique: stereograms take two separate images and challenge the viewer to merge them by crossing his or her eyes.  That will cause the views of the left and right eyes respectively to merge.  Check out the two black & white images below (in the beige border).  Alongside it is the anaglyph alternative.

To pull off the cross-eye trick, many people use their fingers to force their eyes to focus on a nearer object and merge the two background images of the stereogram.

Besides the finger trick, focus on a given element at the center of the picture. Relax your eyes and try to focus your eyes as if staring at something further behind the photo. As your view gradually fall out of focus, the left and right images should fall into each other, creating a sort of displaced view of the main object. It takes some time to master this technique, so don’t be discouraged by drawbacks when first trying it.

For a more visual explanation, check out this video tutorial:

Anaglyphs

Anaglyphs exploit the biological make-up of the human eye to amplify the depth of regular vision. Eyes have two composite elements that allow people to perceive both variations in color and variations of light (and dark). Cones regulate color vision; rods regulate light perception.

RGB

The cones aren’t actually color-coded, but they vary in sensitivity depending on the wavelength of the light. Red light has a shorter wavelength; blue a longer one, and green somewhere in the middle. Remember staring at the TV up close as a kid? You saw red, green and blue because screens are designed to expose a combination of these three colors to project the image.

Your eyes are about two inches apart, so they’ll catch the same image but at different angles, forcing your visual cortex to merge them together.  Now imagine what would happen if you remove red or blue.  You would deliberately change the image you’re looking at.

3D Camera Photo anaglyph 稲美町にて3D Camera Photo parallel 稲美町にて

Now if you separate red from one eye and blue from the other, roughly speaking  your brain will have to merge the two images together at different wavelengths.  That causes different light wavelengths to jump out, and hence the image’s layers separate when your visual cortex jumbles it all back together – all because your color vision was filtered.

3D Camera Photo anaglyph 稲美町にて 23D Camera Photo parallel 稲美町にて 2

There are other color combos this can work with (for instance, green and magenta like mentioned above).  Again, that combo exploits the green and red cones in the eye and leaves blue alone.

Green incorporates elements of the two other colors giving it certain advantages considering most anaglyph 3D is in red/blue format.  For more resources on exploiting the color layouts of 3D pics, check out our resource articles.

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