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What you need to know
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What you need to know

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Stereoscopic 3D means creating the illusion of a room.
By presenting two pictures captured with a horizontal axial distance between the cameras, you replicate the way humans perceive depth. 
Because 3D is our natural way of seeing, it brings a feeling of realism and presence to the audience.
The perception is increased by 300% and your communication with the spectator is far more powerful.
Regardless of whether it is drama, entertainment, commercials or education.

Before you enter the exciting world of stereoscopic 3D, hereinafter called 3D in this text, there are two things you should bear in mind:

  • Think 3D from the start!
  • Converting a 2D idea into 3D is never a successful approach.

 

 

The average distance between the human eyes is 65 mm. Watching an object, your left eye can see more of the left side of the object and
your right eye can see more of its right side. The shape of the object is the same, but what each eye sees is different.
The brain fuses the images into a 3D sense of the size and distance of the object.

Two slightly different views Left eye Right eye

In human eyesight, convergence is the ability of our eyes to alter their optical axes horizontally in an inward direction.
Convergence can be simulated by "toeing" the cameras  - focusing on a depth point in front of, behind or at the screen plane.
The "convergence point" is where the axes of the toed in cameras align on the Z-axis.  Zero parallax is at the screen plane and is often a position in depth used for the point of interest.

Placing all the objects behind the screen (positive parallax) produces a "window effect" looking into the world on the other side.
Placing objects in front of the screen (negative parallax) makes them hover in front of the audience. This is an effect that is frequently used at theme parks and needs to be handled with care. The placement of the objects in a shot, on, in front of or behind the screen plane is one of artistic judgement.

The level of perfection in the human ocular perceptional system is very high. To put it simply, in order to recreate the impression of depth you need two exactly matching pictures but with a horizontal separation. In order to create 3D film, you need two cameras shooting with horizontal separation. This is not easy. We will not go into this just now, but you need a proper rig to mount the cameras correctly.

We have stated that the interocular distance between our eyes is about 65 mm. However, when shooting on set, you frequently have to change the inter axial distance between the optical axes.
As a rule of thumb, it would be true to say that the interaxial distance varies in direct proportion to the distance of the subject from the camera.
The closer the subject, the smaller the interaxial distance. The further away, the larger the distance.

A helicopter shot might require one metre or more, while a macro shot of an ant can be 2 mm.

For the distant shot, the cameras are mounted side by side (parallel). However, for the short interaxials, the opportunities are
physically limited by the thickness of the camera bodies.
A mirror (beam splitter) rig is needed.