A Proposed New Series of Standard Focal Lengths for Motion Picture Projection Objectives

In the early days of motion pictures, projection objectives were supplied in a series of focal lengths which differed from each other by only an eighth of an inch. The burden of making and carrying in stock so great a variety of focal lengths became oppressive for both the manufacturer and the dealer and, in consequence, the Society at its Chicago meeting in 1917¹ adopted as standard a series of focal lengths in which the interval between numbers was a quarter of an inch. This practice has been followed up to the present day. The only further attention given by the Society to the subject of projection lens focal lengths consisted in adopting a standard permissible tolerance of plus or minus 1 per cent.²

Print ISSN

0097-5834

Published

1930-09

Content type

Original Research

DOI

10.5594/J06543