Investigations on the Reflection and Transmission Characteristics of Photographic Plates

A method is described for measuring the reflection and transmission of light by a photographic plate under conditions similar to those met in the ordinary use of the plate. The essential features of the work are the use of photographic methods of measurement and the development of a null method of working which eliminates from the discussion the characteristic curve of the plate the degree of development or contrast, and which requires as a final step only a single measurement of the transmission of an optical wedge at some chosen point. A complete series of measurements was carried thru on several boxes of Eastman 40 plates, all of the same emulsion number. The measurements were made using white, blue, green and red light. It was found that for blue light the plate reflected 25%, transmitted 9%, and absorbed 66%. The reflection and transmission losses increased rapidly with increasing wavelength. The effect of exposure time on reflection and transmission was investigated and no change was found in these factors over considerably greater lengths of time than any of the exposures used in this work.