3-D question?

Question

i just saw Journey to the center of the earth. we got to keep these awsome 3-D glasses when we were done. these werent your run of the mill red-blue 3-D glasses. these looked like sunglasses and were mostly clear from what i saw out of them. so i said, cool. lets watch Shrek 3-D. but it didn't work. there was too much red and blue lines. so my question is,

A: how does 3-D work?

B: are there different kinds of 3-D?

c: what kind is better?

Answer 1

Yes the dark 3D glasses that look like sunglasses use a 3D method called Circularly polarized glasses - this is where the projector quickly flashes two images up on the screen (faster than the eye can catch) but the images are offset so that the left eye sees one image and the right eye sees another your mind blends the images for you, but it tricks it into seeing perspective.

The red/blue glasses are called Red/cyan anaglyph and use the silouette of the images in red and blue of objects in picture that are offset from the original image.

Read more about by looking up Stereoscopy

Answer 2

A. All 3-D systems work by making it so that your eyes see slightly different images.  This simulates how the separation of our eyes means each sees something slightly different, and then our brain interprets the differences to judge depth.

B. There's physical separation, like the Viewmaster, where you hold a different picture in front of each eye.  Good for handheld applications, not so much for theaters.

There's the red-green style, where one image is red and one is green, and you have filters over each eye so that one eye only sees the green image and one sees only the red.  This can also be mixed with color so that you have 3-D monochrome against a color backdrop.

The type most commonly used for movies, though, is polarization.  You have two images projected on the screen with different polarizations, and the lenses block out one image for the left eye and the other for the right eye (look up "polarization" on wikipedia).  The type of 3-D used for Journey and Beowulf has the two lenses at only a few degrees apart in polarization (my theater gave out the same glasses for both, so I know they must use the same tech), so that it's not immediately obvious that there's any difference if you hold them up to another polarizer.

C. The "polarizers at a slight angle" allows for full color and minimal headaches, but it's more expensive and requires finer tuning...it's easier for a sloppily maintained projector to give everyone the swirling willies.  The viewmaster style is probably the best in terms of fidelity of image, but everyone has to watch the thing on their own set of goggles, which kills the point of having a theater showing.

Answer 3

A.  In 'real life' we see in 3-d because each eye sees what you are looking at from slightly different angles.  Hold a finger up in front of you about halfway between your eyes and the computer screen.  Look at the finger, then look at the screen past your finger.  Now close one eye, look at your finger and the screen, now switch eyes.  Notice how your finger seems to 'jump' to cover up a different part of the screen when you switch eye.  

To make a 3-d image we make 2 pictures at once from slightly different angles.  To see the 3-d effect we have to make sure that the left eye sees only the image made by the left camera, and the right eye sees only the image made by the right camera.  That is hard to do when both images are overlaid on each other on the screen.   So we use filters.  That's what the 3-d glasses are - filters.  The left lens filters out the image intended for the right eye, the right lens filters out the image intended for the left eye.  Since each eye is seeing a slightly different image, our brains turn it into 3-d.

B.  The kinds of filters:  Basically there are 2 kinds - polarized and color.  In polarized the projector sends each image to the screen filtered by polarizing lenses that are oriented differently.  The glasses you wear are oriented the same way as the individual projector lens.  So each eye only sees one of the two overlaid images.  If you tilt your head side to side, the 3-d effect will get screwed up because you are changing the alignment of the polarized filters.  The color filters do it a bit differently.  The red lens will not allow the green light to pass, the green lens will not allow the red light to pass.  The advantage of this method is that it is cheaper than polarized lenses and you can tilt your head.

C. Better?   Good quality polarized filters are better, I think.  But the best is with a direct viewer (like a gaf-viewmaster).  With a 3-d viewer the images are not overlaid as on a movie screen.  There is a separate complete image for each eye.