Method and calculator to determine the spatial parallax in a 3-D photograph

In a method of making a three-dimensional lenticular photograph of a scene including a key object and a background object located beyond said key object with respect to a viewer of said scene, said photograph having width D, the method including the steps of exposing with a single-lens camera said scene from a first vantage point, moving said camera laterally with respect to said scene over a distance T and there exposing said scene ffrom a second vantage point, the improvement comprising a method of calculating said distance T including the steps of:

• (a) first calculating a distance V at which an observer will observe said photograph in accordance with the equation:
• V=D/(2 tan (.theta./2)),
• wherein .theta. is a predetermined viewing angle of said photograph;
• (b) calculating a spatial parallax P for said photograph in accordance with the equation:
• ##EQU21## wherein .pi. is 3.1416 and E is a preselected value from 2 to 10 arc minutes representative of the ability of the eyes of said observer to fuse two images of said three-dimensional photograph together;
• and
• (c) calculating said distance T in accordance with the equation:
• ##EQU22## wherein K is the distance between said camera and said key object, B is the distance between said camera and said foreground object, and u is the back focal length of said single-lens camera.

A calculator for use in making a three-dimensional lenticular photographic of a scene including a key object and a foreground object located between a viewer of said scene and said key object, said photograph having width D and being made by xposing with a single-lens camera said scene from a first vantage point, moving said camera laterally with respect to said scene over a distance T and there exposing said scene from a second vantage point, said calculator being for determining said distance T and comprising:

• a base member;
• an inner member which is substantially circular, said inner member being rotatably attached at the center thereof to said base member;
• said base member having thereon a substantially circular distance scale visible about said inner member, said distance scale extending in a first angular direction from an initial angular position L.sub.c in accordance with the equation:
• ##EQU24## wherein L is an angular position about said circular scale from said initial position L.sub.c, K is the distance between said camera and said key object, and K.sub.c is a predetermined closest possible distance from said camera to said key object;
• said inner member having a key arrow thereon extending radially outwardly;
• said inner member further having a tracking distance scale including values for said distance T extending in a second angular direction opposite to said first angular direction, wherein upon alignment of said key arrow with a value for said distance K, said values for said distance T align with values along said circular scale corresponding to the distance F between said camera and said foreground objec, said values for said distance T being predetermined by the equations:
• V=D/(2 tan (.theta./2)),
• wherein .theta. is a predetermined viewing angle of said photograph, and V is a corresponding distance at which an observer will observe said photograph, ##EQU25## wherein .pi. is 3.1416, E is a preselected value from 2 to 10 arc minutes representative of the ability of the eyes of said observer to fuse two images of said three-dimensional photograph together, and P is a spatial parallax for said photograph, and ##EQU26## wherein u is the back focal length of said single-lens camera.