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My question is why do 3d movies have a red and blue"double image" that is basically just a few inches to the right and left of the real image. And how does this help us see the image as "3d". Does it have anything to do with polarized light. And do you need a special computer screen to produce these images because when I use 3d glasses to loot at 3d images on google i still see the see image?

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    $\begingroup$ The red/blue 3D system is different from the modern circular-polarization system. Your post seems to conflate the two. $\endgroup$ Oct 31, 2015 at 20:38
  • $\begingroup$ Your brain primarily interprets depth by seeing how much an object shifts position between your two eyes' images: more shifting = closer. Convince yourself of this by alternately winking one or the other eye. All technologies (red/blue filters, polarized filters, interlaced images, separate screens) are based on feeding your two eyes slightly shifted images to trick your brain into seeing depth. $\endgroup$
    – user10851
    Nov 1, 2015 at 2:31
  • $\begingroup$ I'm voting to close this question as off-topic because it shows insufficient prior research $\endgroup$ Nov 1, 2015 at 8:08

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red/blue double image is the (very) old technology to see 3D on paints, drawings and ordinary screens. See 'Anaglyph' on wikipedia. It requires red/blue glasses (very cheap on Ebay :-) ).

Polarized display is expensive, and is the one requiring polarized glasses.

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  • $\begingroup$ so polarized displays wold be the movie screens at amc or other big movie theaters. $\endgroup$ Oct 31, 2015 at 20:37
  • $\begingroup$ yep. and they are 2 kinds : both using polarized glasses, but not the same. ( parallel vs circular polarization). They are also some theaters with the electronic glasses fastly shuttering each eye in alternance (no polarization, then). $\endgroup$ Oct 31, 2015 at 20:43
  • $\begingroup$ Indeed the display is metallic, it's the projectors which are polarized. $\endgroup$ Oct 31, 2015 at 20:44
  • $\begingroup$ The parallel type didn't last long. It causes headache and confusion anytime you snuggle up to your date put your head on his or her shoulder. $\endgroup$ Oct 31, 2015 at 20:44
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    $\begingroup$ Yeah, but with the circular if you rotate your head at the frequency of light the stereo won't work any more. Nothing is perfect :-p $\endgroup$ Oct 31, 2015 at 20:46

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