isocenter(redirected from mechanical isocenter)
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The unique point common to the principal plane of a tilted photograph and the plane of an assumed truly vertical photograph taken from the same camera station and having an equal principal distance.
The points on a photograph intersected by the bisector of the angle between the plumb line and the photograph perpendicular (i.e., where the principal axis meets the positive or negative plane). On a vertical photograph, the isocenter and photonadir point coincide with the principal point.