The biggest problem with 3D, though, is the "convergence/focus" issue. A couple of the other issues -- darkness and "smallness" -- are at least theoretically solvable. But the deeper problem is that the audience must focus their eyes at the plane of the screen -- say it is 80 feet away. This is constant no matter what.I knew there was some reason beyond hating to wear the clunky 3D glasses over top of my already clunky glasses.
But their eyes must converge at perhaps 10 feet away, then 60 feet, then 120 feet, and so on, depending on what the illusion is. So 3D films require us to focus at one distance and converge at another. And 600 million years of evolution has never presented this problem before. All living things with eyes have always focussed and converged at the same point.
If we look at the salt shaker on the table, close to us, we focus at six feet and our eyeballs converge (tilt in) at six feet. Imagine the base of a triangle between your eyes and the apex of the triangle resting on the thing you are looking at. But then look out the window and you focus at sixty feet and converge also at sixty feet. That imaginary triangle has now "opened up" so that your lines of sight are almost -- almost -- parallel to each other.
Monday, January 24, 2011
Why 3D Movies Will Never Succeed in the Long Run
Here is an interesting physiological fact that explains why 3D movies will never be a truly satisfying experience. This is from Walter Murch, film editor and sound designer, writing to Roger Ebert and published on Ebert's blog at the Chicago Sun-Times:
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4 comments:
Herr Murch may be great at sound, but he must have failed optics. In my physics class we learned that the eye's approximation for infinity is at about 30 feet. That means that as long as you're never required to focus on something closer than 30 feet, your eye will never have any inconsistency between its convergence and its focus. Distances of over 30 feet are common in the theater; I don't see what his problem is.
The one thing I don't like about 3d movies is that they're rarely filmed with unifocus lenses. That problem is easily solved once directors realize that narrow depth of field is a cheesy photography trick (making films look more artsy) that shouldn't apply in 3d cinema. Kubrick's films would have been perfect for 3d because he loved unifocus and detached (no pop-off visuals) filming styles.
Anonymous:
There is more than simple "focus" in seeing objects at a distance. Notice how Walter Murch talks about a strobing effect? You can see this on an ordinary TV (no 3D effect) when people wear striped ties. The refresh rate of the TV and the adjacency of pixels can create the effect. As for 3D, here's an example:
When 3D glasses are out of sync, they pause and wait for the next frame before continuing. Since this happens so fast, you don't notice it. But unless XBMC can interface with that IR hardware and send signals to the glasses, or receive them and drop a frame (depending on who's 3D system you're using) the glasses/frames won't resync on their own. This creates a strobing effect, makes the picture look dimmer..brighter..dimmer, flickering like a candle, and gives most people headaches.
You've latched onto "focus" but Walter Murch talks about focus/convergence, something slightly different. It isn't simple focus.
The image on the screen is more than 30 feet away, so you are right that it is practically at infinity and requires no focus effort. But if you focus on a 3D screen you see blur at times. That's because the image is best seen by de-focusing and converging at a different focal point. This is best illustrated by 2D pictures, autostereograms. You can focus on the flat image and see a pattern, but if you defocus you can suddenly bring a 3D scene to life.
Walter Murch is talking about is that this activity of having to defocus and converge on a 3D image. Evolution has not adapted us to do this easily. It requires a bit of effort and that's why some people get headaches.
You've let your simply physics background blind you to the richness of perceptual experience. It is more than simple focus.
I thought Murch was talking about polarized 3D methods, not synchronized opaque/transparent 3D glasses. As I understand it strobing is not peculiar to the polarized method. If it was, it would be because of interlacing methods, and that will show up on normal 2D film anyway.
I don't really understand the de-focusing part when you say ". . . if you focus on a 3D screen you see blur at times. That's because the image is best seen by de-focusing and converging at a different focal point." I understand autostereograms, but I thought the effort to separate focus from convergence (because of how close you are to the screen) was what caused the difficulty.
My thinking is that in the theater, as long as the 3D image never comes closer than around 30 feet, your eyes' focus won't change and convergence will act independently, just like with real images.
Ah, yes, physics. Education was supposed to be enlightening, but perhaps it clouds more than it reveals?
Anonymous:
Yes, he is talking about the polarized 3D glasses, this is the technique used in Avatar and it requires the viewer to use stereopsis to create the 3D effect:
A stereoscope is a device by which each eye can be presented with different images, allowing stereopsis to be stimulated with two pictures, one for each eye. This has led to various crazes for stereopsis, usually prompted by new sorts of stereoscopes. In Victorian times it was the prism stereoscope (allowing stereo photographs to be viewed), in the 1920s it was red-green glasses (allowing stereo movies to be viewed), in the 1950s it was polarizing glasses (allowing coloured movies to be viewed), and in the 1990s it was Magic Eye pictures (autostereograms). Magic Eye pictures did not require a stereoscope, but relied on viewers using a form of free fusion so that each eye views different images.
The techniques of using an old fashioned stereoscope, or do-it-yourself autostereopsis, or using polarized glasses to create the dual images of stereopsis all end up being the same "exercise" for the eye. You get a sense of depth by altering your vergence to calculate the depth of the image.
As Murch points out:
The biggest problem with 3D, though, is the "convergence/focus" issue. A couple of the other issues -- darkness and "smallness" -- are at least theoretically solvable. But the deeper problem is that the audience must focus their eyes at the plane of the screen -- say it is 80 feet away. This is constant no matter what.
But their eyes must converge at perhaps 10 feet away, then 60 feet, then 120 feet, and so on, depending on what the illusion is. So 3D films require us to focus at one distance and converge at another. And 600 million years of evolution has never presented this problem before. All living things with eyes have always focussed and converged at the same point.
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