3D films were all the rage in the 1950s - they were seen as the next-wave of cinema technology that would get people away from their TV sets and back into the theatres.
But too many film makers treated the process as a gimmick with everything "leaping out of the screen" in an attempt to amaze and impress the audience.
The fad didn't last for very long - people became bored and didn't like having to wear glasses. Perhaps the final death knell was sounded when CinemaScope appeared on the scene. Even though it was only a 2D process, CinemaScope was actually promoted as "the modern miracle you see without glasses" and not all that many 3D films were made after that.
The gimmicky films had tended to overshadow more-serious use of the medium by films such as Hitchcock's Dial M For Murder and Andre De Toth's House of Wax and it is only in comparatively-recent years that interest has been revived.
There are two main systems for 3D films but they both rely on having separate images for each eye and for making sure that each eye sees only the image meant for it.
The "anaglyph" system - which was certainly the most-popular and cheaper
system - used a different colour for each image. The left-eye image was
usually red and the right eye image was usually blue (it used to be green
until NASA research showed that red-blue worked better than red-green).
Glasses with colour filters were then worn to "direct" the proper image to each eye.
The system worked well but was limited in that genuine full-colour reproduction was not possible (although there were some interesting experiments towards the latter days of the 3D boom and significant advances have been made since then).
The other main system used polarised light to differentiate between the two images - it gave much-better results and full-colour. It was used for making Dial M For Murder and House of Wax and is, fundamentally, the system-of-choice today.
Briefly, photons (light "particles") can be forced to line up in a particular plane instead of having natural, random polarisation. Light is said to be polarised when all the photons are lined-up in, say, a vertical or horizontal plane.
With polarised-light 3D films, the left-eye and right-eye images are
projected through filters that result in the light reaching the screen
having a different polarisation for each image. The images are then
"directed" to the correct eye when the viewer wears glasses having
special "polaroid" filters.
There is more than one way of projecting these films. One has each image on a separate film so two projectors have to be used. This gives a very-bright image on the screen but there can be problems. For example, the two projectors must be lined-up with the utmost precision and they have to run exactly in sync - even to the timing of the shutter opening and closing between each frame. Any frame-loss caused by damage to one of the film strips has to be duplicated on the other. A complete loss of the 3D effect can result from them being just a frame or two out of sync.
However, the prints of
Dial M For Murder
and
House of Wax
being shown
at The Astor use the StereoVision process which places the two images
side-by-side within a single frame on the same strip of film.
A special StereoVision projection lens is used to combine the images on the screen and apply the appropriate polarisation to each of them.
The images on the film are pretty-much the "normal" height but, as you can
see in this frame from Dial M for Murder,
they have been "squeezed" horizontally so that they fit in
the space available on the film. An anamorphic (CinemaScope-type) lens
is used in front of the StereoVision projection lens to "unsqueeze" them
to the correct 1.37:1 aspect ratio.
But there's a price to pay for the convenience of having both images on the same film strip. The number of optical stages involved (including filtering) causes of loss of 70% of the light that would normally reach the eye so the images are significantly dimmer than you would be used to seeing at The Astor.
Getting ready to show 3D films at The Astor has been something of an adventure - apart from getting the prints and the special lenses (not to mention thousands of "polaroid" glasses) we also had to get a different screen!
Our usual screen is "matte-white" - that is, it doesn't have any of the special coatings that are often used to try to make the picture seem brighter. Some coated screens - often known as "gain screens" - are not ideal (even for 2D) because they do not give the even light distribution that we feel is essential to the proper presentation of any film format.
Unfortunately, a matte screen does not preserve polarisation. It scatters the light randomly and destroys the 3D effect. You can put on the special glasses but there's none of the "depth" you expect.
Several options were tried but, in the end, we had to manufacture a so-called "silver" screen for mounting on a temporary frame in front of the permanent screen. It was roughly the same size as the part of the main screen used then for Academy Standard ratio (1.37:1) films at The Astor so nobody missed out on any of the big-screen experience.
Dial M for Murder screened for a two-week season at The Astor from Sunday, March 23, to Saturday, April 5, 2003.
House of Wax was shown from Sunday, April 6, to Sunday, April 13, 2003.