Cinematographic annual : 1931 (1931)

86 CINEMATOGRAPHIC ANNUAL This argument is not intended to lead to the conclusion that the distribution of residual color aberrations in a lens is a matter of no concern and that it can be left to chance with the certainty of acceptable performance but it is intended to show that there is no reason to believe that slight changes in the type of color correction of motion picture lenses will result in any better average performance. The test proposed above is a laboratory test in that it eliminates practically all of the uncertainties which are able to lead so easily to false conclusions when lenses are tested in the ordinary way but at the same time it is a practical test in that it is photographic and its results are interpretable without much effort of the imagination. They are identical with an enlargement perfectly executed of a photograph taken in the ordinary way but on a practically grainless infinitely thin emulsion with almost perfect precision of focus and with a perfect camera. The tests need nothing to supplement them to disclose all the characteristics of the performance of a lens except a test for distortion. This, in fact, could be determined from a test of this sort but it would have to be carried out in a somewhat different manner. C1) Bielicke, American Cinematographer, September, 19 28, page 13. (2) Dubray, American Cinematographer, November, 193 0.