Given our on again – off again fascination with various 3-D imaging technologies, including 3-D movies, are these imaging technologies completely compatible with our visual physiology's ability to perceive depth?
By: Ringo Bones
The now famous 3ality Digital Systems, Inc. – thanks to James Cameron’s Avatar movie – had come a long way since the company presented their “White Paper” describing their flat-panel auto stereoscopic technology at the Stereoscopic Displays and Applications Conference in Santa Clara, California back in January 2003. The company’s widely technologically compatible to current movie theaters – not to mention economically viable – 3-D imaging system had added the “third dimension” to the previously 99.99% of all images that are monocular in nature. But, is this latest incarnation of the 3D movie really physiologically compatible to the way our eye-brain system perceive binocular / stereoscopic images – or even reality?
Most previous 3-D movie imaging systems that had managed to gain commercial viability include those red / green, red / green 3-D glasses for viewing monochromatic / black and white 3-D movies made during the 1950s. Improved colored 3-D movies made during the 1970s and the 1980s that require Polarized 3-D glasses to view them, LCD shutter IMAX technology, experimental holography exhibited in various consumer electronic trade shows during the early 1990s. And some more esoteric 3D imaging systems that work on the principle of density delta / persistence of vision. Not to mention jiggle-vision, which is a 3-D movie system where the camera constantly moves up and down a small amount to give the brain what needs to construct a 3-D world as long as proper moving cues exist in the film.
On the 3-D still picture front, we had the now rare “stereo” photos that need those 1950s era red / blue and red / green 3-D glasses to perceive the “depth” of the third dimension. Much improve ones that use polarized 3-D glasses to direct the left and right images to the “right” eye to impart a perception of depth. The old stereoscopes from the Victorian era, really expensive still holograms and zography – 3-D still pictures whose depth dimension is imparted via a vertical lenticular surface. Although in terms of bang for the buck performance, nothing beats the good old 1970s era (even though it was first marketed way back in 1939) View-Master 3-D slide show device. During my exploration of still 3-D imaging systems since childhood, only the Victorian era stereoscope and the View-Master 3-D are the most likely still image 3-D viewing systems one would encounter this day and age.
When it comes to the matter of whether these systems are truly physiologically compatible to the way our ear-brain system perceives depth, most of these visual cues can be supplied by either our left or right eye. Unfortunately, there are certain cues to depth and distance that can be obtained only when both of our left and right eyes are working together. By focusing both eyes on the same object, our eyes register images that vary slightly because our eyes themselves are on average two and a half inches apart. In fusing the two images, our brain notes the slight disparity between them and uses it as a cue to a composite three-dimensional image.
The ability to combine two different images is called stereoscopic vision, and is the principle behind how a stereoscope works. Stereoscopes were as popular in Victorian-era living rooms as TV is in our present living rooms. A typical stereoscope requires two separate of a scene – known as a “stereo pair” – taken from slightly different angles. These photographs are put into a small viewer, which permits one photograph to be seen by the left eye and the other by the right eye. The brain accepts the disparity between the pictures as normal and blends them into a three-dimensional or 3-D view. The much improved 1970s era View-Master works the same way as a Victorian-era stereoscope, except that the View-Master uses color film slides instead of photographs.
The curious disparity exaggeration - or the “Diorama Effect” I noted when watching the 3-D version of the movie Avatar – was mainly caused by the muscular action of our eyes that also play a role in depth perception. This remarkable but still little understood range-finding process of our eyes enables us to estimate both the distance to various objects and the distance between the objects themselves. The process – most efficient at distances up to 20 feet – depends for its cue on the on the muscular convergence of our eyes – i.e. their inward movement as they turn to focus. Since our eyes must turn more to see a near object than a far one our brain automatically “measures” the amount of convergence and adjust its stereoscopic depth perception accordingly. Thus making scenes in the 3-D version of the movie Avatar that fall within the 20 to 30-foot scale seem to have the most seamless sense of depth and dimensionality. Especially the shots where the 3ality 3-D cameras are only 10 to 20 feet away from those Bell UH-1 Huey / Iroquois type transports.
The disparity exaggeration / Diorama Effect of our eyes depth perception is not only the preserve of stereoscopes, View-Masters, and 3-D movies, but also of us looking though a pair of binoculars. This phenomenon is very noticeable when you find yourself lucky enough to use one of those “pay-per-view” binoculars on the observation platform of the Empire State Building, or by peering through a medium powered – 12 X 50 – binoculars while riding on a helicopter in a scenic flight / aerial tour over the Manhattan skyline or over Dubai. This disparity exaggeration that produces the stark cardboard cut out Diorama Effect – a very curious stereoscopic effect that draws the viewer to the scene. Thus giving him or her the erroneous impression that he or she is looking at a highly detailed scale model, rather than a real skyline of a real city. Like those moderately distant trees and rock outcroppings in the movie Avatar. Maybe the tech guys at 3ality Digital Systems who designed the proprietary software that runs their 3-D cameras should take note of this curious visual effect and find ways to compensate for it to make their 3-D system more physiologically compatible to how our eyes perceive depth.