1. How we perceive depth:

Eyes 2.5 - 3 inches apart
Therefore the image each eye receives is slightly different.
The light from distant objects is roughly parallel and the lens of the eye is relaxed.

However the light from close object travels at different angles.
When we look at a close up object - eyes converge on it like a couple of searchlights, at the same time the muscles that squeeze the lens have to do more work to keep the object in focus

Significance of this we shall see later…..

Let's ask Spencer Kelly to explain more fully.

3D .- How it Works - The Optical illusion - Click on line (3D Cinema makes a fresh comeback)

This depth perception, which depends upon our brains analysing the slight differences between the images in our two eyes is called Stereopsis.

NB We see with our brains - which "Normalise" all the visual data we gather.

Club experiment

With both eyes open - point at something.
Close the left eye…are you still pointing at the object?
Now open the left eye and close the right eye
Are you still pointing at the object?
This is called Ocular dominance, or "eyedness"

Nothing to do with 3D - but interesting !
For more see http://en.wikipedia.org/wiki/Ocular_dominance

2. Creating the illusion

To make 3D imagery work, two images are recorded / photographed at the same time, but from slightly different viewpoints (mimicking each eye)

3. Viewing the Illusion

In creating the 3D effect the image recorded for the left eye must be seen only by the left eye, the image recorded for the right eye only by the right.

There are various techniques to achieve this:

a) Steroscope - e.g. Viewmaster


b) Anaglyph glasses

Anaglyph (Greek ana+gluphein - "to carve")
Red/Green or Red/Blue (cyan) lenses. Red is usually on the left.
In this system, two images are displayed on the screen, one in red and the other in blue (or green). The filters on the glasses allow only one image to enter each eye, and your brain does the rest.

Passive system - Good for Black and white images.
First 3D movie 1922 "The Power of Love"
Possible to do it in colour, but requires some clever image tweaks.

Video explanations on the web:
Bobby Nishimura explains using a pair of anaglyph glasses and some light filters.

You can look at Anaglyph 3d images and movies on an ordinary computer screen. There are many anaglyph videos on You tube - all you need is some anaglyph glasses.
Vimeo Anaglyph channel: http://vimeo.com/channels/stereoscopic3d
Main drawbacks : Ghosting and colour rendition:

Make your own 3d Photos and Videos
Use image editing software or something like:

c) Shutter glasses (expensive):

Used for 3D TV. Glasses sync with rapidly changing images on the screen.

d) Polarised Glasses

This is another passive system. This is used in cinemas and some TVs

Light normally vibrates in all planes . Polarised sun glasses cut out all light except vertical. With 3D glasses - one lens is vertical, one horizontal and two images are projected, one using horizontal light - one vertical. Special silver projection screens are required to reflect more light, since the polarising cuts down the brightness.

Projector about Pounds 30,000 - but glasses are cheap. Now developed for TV by LG.
There are lots of competing projection technologies.

e) 3D with no Glasses (screen technology)


f) 3D video with no Glasses (cross your eyes!)


Sit about 2 feet away from the computer screen. Full screen seems to work well.

Then once you have mastered the technique, take a look at these images.

…and take a look at this movie
3D movies sample.(Cross-eyed)

4. Transmission formats


The Club 3D PC which uses Nvidia shutter glasses has a software player for Side by Side 3D movie files.

5. Health concerns:

2-3% cannot see 3D at all due to eye problems
2-6% eye strain and nausea due to mismatch between convergence (where your eyes point) and where they focus. In the real world, and 2D movies, both are the same point.

In 3D video the convergence distance varies, and can be either deeper than the surface of the screen or in front of it, while the focus point is fixed (the screen).

6. More on 3D

"Click on line" video clips:

Converting 2D to 3D

Filming 3D with a single lens 3d camera

Holographic TV - The new TV?

Mark Kermode - How to enjoy a 3D Movie

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