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3D              at the movies


                                                                Mike Trickett

            he  perception  of  depth,  the  ability  to
        Tperceive  the  world  in  three  dimensions,
        comes naturally to humans because each of our
        eyes,  set  about  70  mm  apart,  sees  a  slightly
        different view which, when combined by our
        brain,  gives  us  the  perception  of  depth.  The
        closing of one eye removes that perception.

        The means by which three dimensional (3D)
        images   (sometimes   called   stereoscopic
        imaging) can be recorded and viewed has been  Various devices offering this were popular in
        known  for  as  long  as  the  recording  of  the  late  1800s  through  to  the  mid  twentieth
        photographic images has been possible.  century.  All  of  these  items  were  for  direct
                                             viewing of the images by a single person and
                                             relied upon the device’s ability to convey the
                                             left and right image to the appropriate eye.

                                             The viewing of a 3D image by a large number
                                             of  people  is  a  far  different  matter.  The
                                             projection of the two images required to form
                                             a three dimensional image is a simple enough
                                             matter, but to ensure the viewer sees only the
                                             left  and  right  images  with  the  correct  eye
                                             requires a method of separation, achieved by
                                             the  wearing  of  some  type  of  glasses
        Hand held stereo viewers were a very popular  incorporating  suitable  filters.  A  number  of
        item from the 1880s to the 1920s.
                                             systems were devised, tried and faded away in
        The  recording  and  direct  viewing  of  a  3D  the years prior to what could be called the 3D
        image is a fairly straight forward procedure. A  frenzy of the early 1950s.
        camera or cameras with the lenses separated by
        roughly  the  same  distance  as  our  eyes  will  The 1950s brought a number of changes to the
                          record  two  slightly  film  industry  (larger  screens,  stereo  sound,
                          different   images  etc), many of which were an attempt to counter
                          which,  when  viewed  the impact that the introduction of television
                          separately by the left  (in  the  USA  at  that  time)  had  on  cinema
                          and  right  eye,  will  audiences. Three dimensional films were just
                          recreate   that   3D  one aspect of that innovation by the industry.
                          image.
                                             The recording of motion in 3D requires the two
                                             images  to  be  recorded  on  film  or  films  in
                                             perfect time with each other. In the case of a
                          The stereo viewer
                          was a popular family  color film, the two images must be matched for
                          entertainment item in  the same color rendering. Cinema projection
                          the late 19  Century  could be a problem, as perfect alignment of the
                                  th
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