I reccently went on a college trip to Bradford Media Museum. While i was there i went to see a IMAX movie which was a 3D movie about dinosaurs. I havent been to a IMAX movie since i was a little kid so i was looking forward to seeing one again now that i could appriciate it alot more. I was very impressed at the effect that the movie gave there was so much depth and the dinosaurs really did feel like they were right in front of you. There was one part of the film inpiticular that really impressed me when a archeologist was digging up some earth and the camera panned round and the earth was thrown directly at the camera it really did seem like you were meant to get covered in the earth, it was a real shock. During the film i took my glasses off to view the image in 2D and saw that the image seemed to be layored with what i could only think could be different colours that would pass through the glassed at slightly different times to give the effect of a three dimensional image.
I wasnt sure how the screen worked so i did some research to find out a bit more about the IMAX. The IMAX cinema was opened in 1983 (when the Museum was called the National Museum of Photography, Film & Television) and was the first ever IMAX cinema in Europe. The screen at the Museum is 48' (14.63m) high x 65' (19.81m) wide and it ahd to be lowered into the auditorium through the roof as there was no other way to install it. The screen is perforated with thousands of tiny holes to allow the crystal clear sound to flow through it freely. To create the illusion of 3-dimensional depth, the IMAX 3D process uses two camera lenses to represent the left and right eyes. The two lenses are separated by an interocular distance of about 64 mm/2.5 in., the average distance between a human's eyes. By recording on two separate rolls of film for the left and right eyes, and then projecting them simultaneously, we can be tricked into seeing a 3D image on a 2D screen. The IMAX 3D camera is very cumbersome, weighing over 113 kg. This makes it extremely difficult to film on-location documentaries.
There are two methods to creating the 3D illusion in the theatre. The first involves polarization. During projection, the left and right eye images are polarized perpendicular to one another as they are projected onto the IMAX screen. By wearing special eyeglasses with lenses polarized in their respective directions to match the projection, the left eye image can be viewed only by the left eye since the polarization of the left lens will cancel out that of the right eye projection, and the right eye image can be viewed only by the right eye since the polarization of the right lens will cancel out that of the left eye projection. Another method for 3D projection involves LCD shutter glasses. These glasses contain LCD panels which are synchronised to the projector which alternates rapidly at 96 frames per second between displaying the left and right images which are momentarily viewed by the appropriate eye by allowing that eye's panel to become transparent while the other remains opaque. While the panels within these active-shutter 3D glasses alternate at 96 frames per second, the actual film is displayed at 24 frames per second. One particular problem that 3D movies face is that the 3D effect does not extend past the boundaries of the physical screen. It is for this reason that the screen must be large enough to cover as much of the viewer's peripheral vision as possible. Another problem with IMAX 3D movies is due to an inherent difference between our eyes and the film format. Because of the large negative, depth of field is dramatically reduced, causing an often distracting depiction of the scene. Computer-generated imagery films do not have this problem as they are able to control the depth of field in the images to allow everything to be in focus. While some may argue that this is less artistic than regular 2D films that purposefully employ shallow depth of field for aesthetic reasons, IMAX screens take up more of the viewer's vision than regular 2D films, and therefore the viewer can be disoriented by seeing images that are out of focus. The biggest 3D IMAX screen is located in Melbourne, Australia.