Human eye has binocular vision i.e. we see with two eyes, which are placed side by side, and each eye sees the object from different angle so this difference is calculated by the brain as depth. This what is 3D effect or Stereoscopic vision.
Appreciation of 3D effect is more in near field, as the near objects make more different angles so depth perception is better but as one looks at for field this angle difference is less, so depth perception in for field is less.
In above picture both each eyes are producing different images of same object at same point of time.
To mimic these binocular images for making 3D movies camera used also have two lenses separated by each other just like human eye (stereoscopic cameras)
|3D or Steroscopic camera|
So acquired images from two lenses are then displayed in grossly three techniques to make 3D effect
1 cyan or red coding
3 Eclipse Technique
Cyan and red coding :-This is technique which is not used in commercial films these days. But one can try make 3D movies with this technique in your house with your ordinary computer or regular 2D TV. You need glass like shown below or make it by your self.
In this technique, the two channels with red filter to left eye and cyan filter to right eye are created. Anaglyptic images can be created with camera or computer generated animation with tcolor coding . both images are mixed and displayed together. A person wearing colored glasses .each eye can see only one image and brain reads it as depth or 3D effect . Images produced by this technique will display less colors.
|Red and cyan 3 D Glasses|
Glass for viweing images like below
Polarizing ligiht:-Normal Light is electrical vector is spread in all direction this is called un polarzied light
In above image on can see vector of light which is spreading in all directions (left hand side) as it passes through horizontal bars only vertical component is let to pass and horizontal component is reflected back now this polarized light.
How is this useful for, 3D movies?
We can create two channels one with horizontal bars and other with vertical bars. If the observer seeing though the bars one with horizontal and other with vertical bars. His each eye can only one image so we can feed two images shot from stereoscopic camera and create a depth perception
In realty bars are not used for this purpose except in microwaves where wave lengths are more. For 3D movies one can use crystal which have this property.
Wait there is problem if observer tilts his head he will not be able to see from both eyes. For solving this problem circular polarization is used one with clockwise roataion and other with anticlockwise rotation
Eclipse Technique :-I n this technique each eye is blotted alternatively with shutter in each glasses and in coordination with this images are shown over the screen for corresponding eye in rapid succession this creates illusion of 3D effect there is sensor control of projector and glasses for coordinating shutter blotting /closing and flashing corresponding image.