Panaflex User's Manual, 2nd Edition

Focusing PANAVISION Lenses

Every PANAVISION lens is calibrated individually to achieve optimum optical performance. Lenses are calibrated against a standard flange focal depth of 2.2500in, 57.15mm, at an aperture of T2.8 (or at the minimum stop above T2.8) and an index mark is engraved on the lens to indicate the best possible image at that aperture. Lenses are calibrated at all marked focus distances.

Lenses are then further calibrated at maximum aperture and any difference from the T2.8 setting is noted. If there is a significant difference between the position of the T2.8 and the full aperture mark a second (shorter) mark is engraved and this is colored blue. The apertures to which it refers are also colored blue.

This extensive calibration ...