AV News 179 - February 2010
If you take two photographs of the same scene, either with two identical cameras
or by moving a single camera a few inches between shots, you can capture any
scene in the same way that each eye would see it. When the photographs are
printed and viewed side by side, it is possible to de-focus your eyes so that a
"third image" - though not the type we usually associate with AV, materialises
between the two. This composite image will be seen as having an illusion of
depth. This technique was popular with Victorian photographers and a quick
search on the Internet will reveal many examples.
Various devices were made to assist viewing the two images, with the best
known being the Viewmaster type device with its circular disks of 3D pictures.
Brian May says that his first introduction to 3D photography was the VistaScreen pictures given away with Weetabix packets in the 1960's!
Projecting a 3D image on to a screen, either as a movie or a still image, has
always been a lot more complex than viewing a printed picture. To get the best
effect, two projectors need to be used, with a polarising filter on each one rotated
through 90 degrees. The audience need to wear cross-polarised glasses so that
each eye only sees the 'left' or 'right' projected image. The projectors need to be
fully aligned and synchronised for the effect to work.
An alternative method is to use
"anaglyph" images, where the
audience wear coloured gel glasses,
typically red and cyan, for a similar
(but not as good!) effect. This method
is much cheaper as the anaglyph
glasses are inexpensive and crucially
the image can be projected on a single
projector instead of having to use two.
I did a quick demonstration of this
method at a talk to the Yorkshire AV
Group at Bradford. It's a relatively
simple procedure and I've itemised the steps needed:
1. Take your photographs. For best results you can use two cameras, or one
camera moved laterally between the two images. Its possible to buy (or make if
you're talented enough) a sliding tripod head to assist with this, but for the casual
photographer its enough to take your second image by moving abou Ё