Okay, not exactly everything. But a great deal of information at least on how the various technologies work. Being a 3-D filmmaker and buff, I figured I'm at least somewhat qualified to write this blog and maybe even set a few myths straight.
HOW 3-D VISION WORKS
First thing worth mentioning is how we see in 3-D at all. Humans are a rare species of animal as we are one of the few to have two eyes in the front of our face. A large number of animals have their eyes on the sides (such as fish). As a result, we see stereoscopically and they don't. For it takes two eyes in front of the face to see in 3-D. Each eye sees the world slightly differently and our brain tricks us into seeing the image whole.
Here's a little demonstration of the above. Hold your finger up roughly 12 inches in front of your face. Now blink each eye. You'll note that the left and right eye each see a slightly different part of the finger. This is also why when you were a little kid and you used to bring the pencil real close to your eyes, it seem to split into two.
Euclid and Leonardo Da Vinci had various theorems about stereoscopic vision and how our eyes work and there are books and websites all over the place on it, so I'm just going to skip ahead and get into the actual movie technologies of 3-D. One book, if you're interested, available as a free download online, is Foundations of Stereoscopic Cinema by Lenny Lipton. In the early part of the rather lengthy book, Lipton goes into the history of the science of our stereoscopic vision.
In terms of the movies, 3-D movies operate on the same basic principle as our vision. The average movie is shot with a single camera and a single lens, or eye if you will. 3-D movies are shot with either two cameras or a single camera with a special attachment, usually known as a beam splitter. The left and right eye views of each shot look just slightly different from one another and when viewed through the 3-D glasses, our brain tricks us into seeing the two images as one.
In terms of movies and TV there have been four main types of 3-D done throughout the last 90 years. They are anaglyphic, polarized, field sequential, and the pulfrich illusion. Field Sequential and Pulfrich are mostly for TV, so I'm not going to bother with them here. Maybe in a future blog.
ANAGLYPHIC MOVIES
Anaglyphic 3-D is probably the most familiar type of 3-D out there. I once referred to it, in fact, as the stereotype of 3-D. It's the type that has been used not just in movies, but in comic books, magazines, posters, T-shirts, photographs, and just about any other type of print form of 3-D. This is the type that uses opposing colored glasses. Most people say red/green, but actually red/cyan is the more commonly used type for movies and red/blue for comic books. Yellow/blue--which is tradenamed ColorCode--was used for the 3-D Super Bowl commercials and the Chuck episode earlier this year and magenta/green has been used on some recent 3-D DVDs (while others use red/cyan, go figure). This is, in some ways, the projectionist-proof form of 3-D in that no projectionist can screw it up (unlike polarized 3-D). The two images are printed on the same strip of film using the opposing colors. The glasses cancel out their color and our eyes each see the opposing color. We then put things together in our brain for the 3-D image. Pretty simple. Again, no projectionist can screw up the showing and no special screen are necessary. It can even be shown on TV. But, there are plenty of cons associated with this form of 3-D.
For one thing, though no projectionist can screw it up, any printing lab can. The colors have to be printed precisely or else the effect won't work. This goes for the glasses as well. This is also why until recently it has rarely worked on TV. The tubes in the standard CRT based tv vary their colors ever so slightly and therefore almost never match. Computer monitors and modern flat screen TVs have better color control, so 3-D, if printed right, does work on them.
Also, color anaglyph (sometimes called polybiochromatic!) plain out stinks. The glasses weaken the other colors in the film and if you're going to shoot a color anaglpyh film, you have to watch your color scheme (which people rarely do). I'm also not convinced that the depth in the color anaglyph image is as good as it is in the black and white image, but that might just be me.
The other big knock on anaglyphic 3-D is the amount of misinformation that swirls around it. For several years now, no end of so-called experts--just including one Roger Ebert (who must have been traumatized as a child by a 3-D movie since he so passionately hates them)--have posted over the internet and other media that all previously made 3-D movies were in the anaglyphic format. WRONG!
Now, first off, Ebert should know better since him and Siskel were reviewing films like Spacehunter and Jaws 3-D on their TV show in 1983. Come to it, if you look hard enough, their reviews of those movies might even be on Youtube. I still have my Jaws 3-D glasses and they were not red/blue, they were polarized. Beyond that, showings of 3-D movies from past years pop up every so often. The glasses are almost always polarized.
It is true that the earliest 3-D movies were anaglyphic. I've seen a couple from the 1920s and the three Pete Smith shorts (1936-1941) were all anaglyphic. There were a couple of early 1950s shorts shot that way, too. And post the 1950s, there has been a handful of movies released in anaglyphic format (the most recent being the two from Robert Rodriguez). But, every 3-D feature of both the 1950s and the 1980s, and most of the ones from the 1970s and 1990s, were polarized, not anaglyph. So where did this stupid rumor come from?
Two sources, I think. In the 1960s and 1970s, Columbia and Universal released to the home market on Super 8 and 8mm a couple of titles in anaglyphic 3-D. They were digests of Creature From the Black Lagoon, It Came From Outer Space, The Mad Magician, and the two 3 Stooges shorts. Likewise, in 1972, Universal had an idea to reissue Creature and ICFOS and did so in anaglyphic format. And in the late 1970s, Universal's 16mm rental outfit, Swank, rented anaglyphic prints of Creature, Revenge of the Creature, House of Wax, Dial M For Murder, and ICFOS. Similarly, another outfit called Kit Parker films released The Mad Magician, The Maze, and the two 3 Stooges shorts. This is also around the time the 7 anaglyphic porns made by Stephen Gibson were in circulation (met Steve, once. Nice guy and a 3-D enthusiast, but his choice of subject matter is unfortunate). And in the early 1980s, a company called 3-D Video Corporation--headed by, among other people, Dan Symmes (a 3-D expert)--coverted several 1950s titles to anaglyphic 3-D for broadcast on TV (none of which work, btw). The last of the 1950s films to show up on TV in anaglyph format was John Wayne's Hondo in 1991. So, that could explain where the rumors come from. But they are still wrong.
POLARIZED 3-D
Polarized 3-D is the better version of the format. There's been 3 major variations on it over the years: dual strip polarized, single strip polarized, and digital polarized (which is the modern form).
The 1950s movies were shown in dual strip polarized. This is arguably the best form of 3-D you can find. Each eye is shown through a separate projector. The two projectors are locked together with a mechanism and are (supposed to be) running in perfect synchronisation. The images are each shot through a cross polarized lens onto the screen and the glasses do the rest. The primary benefit to all this is since each image is going through it's own projector, loss of light is minimized. The image is brighter and sharper looking, which also makes for better depth. The primary con is that any lazy projectionist and/or theater owner can (and frequently did) screw it up.
For one thing, polarized 3-D requires an actual silver screen. White screens de-polarize the light which destroys the effect. And the screen needs to be silver and not just silver painted. But there were cheap theater owners who simply applied a paint of silver coat to their screens thinking that would work. It didn't. Also, the projectors, as noted above, needed to be in synchronisation. Projectionists would let them go out of synch and then not bother to fix them. To give you an idea of what that might look like, imagine watching a scene of somebody talking. Now imagine your left eye seeing them with their mouth open or their arm raised and the right eye seeing the arm down and the mouth closed. It's what's called retinal rivalry and it was the leading cause of the infamous 3-D headaches. Not the glasses, but the projection of the image.
In 1966, Arch Oboler, the man who started the 1950s craze with Bwana Devil, thought he had the synchronization problem beat. He developed a system where the two images were printed on the same strip of film (known as single strip polarized!). The images could be printed side by side or over and under (the more common version) and then shot through a special box known as a beam splitter. The beam splitter contained both polarized lenses. Oboler's idea also eliminated the necessity of having an intermission, which every 1950s film had (so the reels could be changed). While Oboler's idea looks good on paper, what he failed to take into consideration is the stupidity of the American projectionist and/or theater owner. If they could screw it up, they would.
For one thing, we were back to needing the silver screens (all polarized 3-D films need silver screens actually). If the theater didn't have one, you knew the effect wasn't going to work. Projectionists would fit the beam splitter on incorrectly in any sort of manner, including reverse 3-D (the background would pop out and the foreground would recede into the screen!). Think that's funny? I've seen it. At a 1996 showing of Dial M For Murder, the first 40 minutes were shown in reverse 3-D. Very aggravating. Also, if the film broke and the projectionist spliced it, if they didn't splice the corresponding left and right images, we were back to non-synched 3-D. Yuck. Combine that with the truly crappy 3-D movies released in the 1970s and 1980s and it's no wonder it didn't last.
Digital polarized might well be idiot--I mean projectionist--proof. The modern form uses a digital projector, a screen set up in front of said projector, and a silver screen along with circular polarized 3-D glasses. The film is made up of jpegs and put on a hard drive. The image alternates 144 times a second--6 times faster than the standard 24 frames per second film projector. Each second is composed of 72 movie images (36 left, 36 right) and 72 black images. The left image is shown, then a black, then a right. The special polarized screen in front of the projector also alternates the 144 times a second, changing the polarizing filter. Persistence of vision and the sheer speed of the projector allow us to see the 3-D image. And with the circular polarized glasses, you can do the one thing no other form of 3-D allows--tilt your head. Again, this seems to be projectionist proof, or maybe I've just lucked out and seen some competent showings. Only time will tell.
Okay, I hope you all took notes. There will be a test later. ;)
Next time I'll sing the praises of Hitchcock and/or Spielberg. See ya at the movies!
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