How 3D works
If you don't know how 3D photography works, here is a brief summary:
Objects look solid and 3D to us because we have two eyes, separated by a few centimeters, that see things from different points of view. The brain interprets these different
images and creates a 3D illusion from them. The problem for photographers is to somehow get two separate images to two different eyes without interference using a 2D
medium.
ViewMaster
The GAF ViewMaster and other such systems use a viewer with two lenses
each of which view a separated image on a circular reel.
The principle has been around since the 19th century and gives great
results for still photographs but is no good for the cinema.
Reels are still manufactured and original ViewMaster machines are
valuable.
Anaglyph
The classic red/blue glasses method, great for those black and white movies of the
1950s. Red and cyan may be used for projection and for viewing. One colour image
for each eye.
Can be used for 3D and also for showing two different images, as Jack did on his
Jackyll and Hyde picture.
Not so great for colour images but it works, kind of.
Polarised glasses
Polarised glasses have relatively clear and uncoloured lenses. Each eye lets light
with a different orientation through.
The advantage of this method is that it works well for colour images, viewed without
the glasses the image is acceptable too, but obviously it won't work for printed
pictures, tv or computer screens.
Used a good deal for recent films.
Pulfrich
This system uses glasses featuring a dark lens and a clear lens. It's a curiosity of the human system that images seen through the clear lens
reach the brain slightly faster than images seen through the dark lens.
With properly sequenced movement recorded on film or video, objects moving across the horizontal field of
vision create the
illusion of 3D.
This has been used on tv a lot - the give away is that there's an excess of right to left motion across the
screen. Without the glasses, the image looks normal.
Lenticular
The image is prepared in a special way, then a lens consisting of a large number of vertical clear plastic prisms is placed
over it.
This technique has been around a long time, being popular in the 1950s and 60s on bubble gum cards.
It is still used a lot and was famously used on the cover of a Rolling Stones LP.
The image may also change as you move past it with an effect similar to that shown in the Logan's Run film.
The effect seems to work better with drawings and cartoons or inanimate objects.