Pentax Optio 33L Operating Manual page 60

Viewing 3D Pictures with the Parallel method and Cross method
Because our eyes are positioned about 6 to 7cm apart, each eye sees
at a slightly different angle. The brain processes this difference to
produce a three-dimensional image. This principle is applied to taking
and viewing 3D pictures.
3D pictures can be viewed by the Parallel method, where the left and
right lines of sight are parallel (like looking far away), or by the Cross
method, crossing the lines of sight. Viewing a 3D picture without the
viewer may take some practice.
Assembling the 3D Image Viewer
Assemble the supplied 3D Image Viewer as shown below.
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