To explain, the convergence point - the point at which the left and right eye images align - sets the location of convergence at the screen plane when the image is projected, with objects in front of this point appearing to be in front of the screen, and those behind appearing to be beyond the screen.

This is because when the two camera images are superimposed on top of each other in alignment terms, the object in question has zero parallax, so appears to be at the same distance from the viewer as the screen onto which it is being projected.

This first image shows convergence on the camera rig, with virtually all the objects contained within the image appearing behind the screen plane.

Images curtesy of Pietro Carlomagno - www.carlomagno3d.it - and taken from the set of 'Inferno'.

To better see the point of convergence place your mouse cursor on the image as this will always be located at the screen plane. You can then quickly see which objects are in front or behind the screen plane.

This second image has the convergence point set on the crew pushing the camera dolly with the camera, dolly and camera operator in front of the screen plane.

Images curtesy of Pietro Carlomagno - www.carlomagno3d.it - and taken from the set of 'Inferno'.

The final image in this sequence has the point of convergence set at the rear wall, with all other objects within the image appearing in front of the screen plane.

Images curtesy of Pietro Carlomagno - www.carlomagno3d.it - and taken from the set of 'Inferno'.

This explains the concept of image convergence, and its link with the screen plane, but as will be seen this is not the end of the story.

Next Page - Parallel or Converged?

As always, test before committing to a particular style of stereoscopic 3-D shooting.

Or better still, contact steve@digitalpraxis.net for more info.