Artificial Sunlight for Photographic Sensitometry

Photographic sensitometry was first put on a scientific basis by Hurter and Driffield (J. Soc. Chem. Ind., 9: pp.455-469) in 1890 with their classic paper, Photo-chemical Investigations and a New Method of Determination of the Sensitiveness of Photographic Plates. Hurter and Driffield used a sperm candle (the British standard of candle-power at that time) for their illumination. While many improvements have been made in their sensitometric procedure, a satisfactory standard quality of illumination has not yet been generally adopted. In both research and the testing of light sensitive materials, particularly those used for negatives, light sources having relatively low color temperatures (such as the candle, acetylene flame, or Mazda B or C lamp) will not give data consistent with actual practice. Different types of photographic emulsions (ordinary, orthochromatic, and panchromatic) have widely different spectral sensitiveness, and relative speeds determined by the use of unfiltered artificial illuminants will be radically different from the relative speeds under sunlight, to which the great majority of photographic negative materials are exposed. The problem has been thoroughly considered in a report on “The Unit of Photographic Intensity” (Special Committee, Optical Society of America, L. A. Jones, Chairman, J.O.S.A. & R.S.I., 12: pp. 567–586; June, 1926).

Print ISSN

0096-6460

Published

1928-04

Content type

Original Research

DOI

10.5594/J08117