Definition

The perpendicular distance from the internal PERSPECTIVE CENTRE to the plane of a particu­lar finished NEGATIVE or PRINT. This distance is equal to the CALIBRATED FOCAL LENGTH corrected for both the enlargement or reduction ratio of the film or paper shrinkage or expansion and maintains the same perspec­tive angles at the internal PERSPECTIVE CENTRE to points on the finished NEGATIVE or PRINT, as existing in the taking CAMERA at the moment of EXPOSURE.