Sensitometry is the scientific study of light-sensitive materials, especially photographic film. The study has its origins in the work by Ferdinand Hurter and Vero Charles Driffield (circa 1876) with early black-and-white emulsions.[1] They determined how the density of silver produced varied with the amount of light received, and the method and time of development.
Plots of film density (log of opacity) versus the log of exposure are called characteristic curves,[2] Hurter–Driffield curves,[3] H–D curves,[3] HD curves,[4] H & D curves,[5] D–logE curves,[6] or D–logH curves.[7] The overall shape is a bit like an "S" slanted so that its base and top are horizontal. There is usually a central region of the HD curve which approximates to a straight line, called the "linear" or "straight-line" portion; the slope of this region is called the gamma. The low end is called the "toe", and at the top, the curve rounds over to form the "shoulder".
Usable values of gamma are typically between 0.8 and 1.2. (But values of up to 1.5 may be useful for slides). A full set of HD curves for a film shows how these vary with developer type and time.[2]
See also
References
- ^ Hurter, Ferdinand & Driffield, Vero Charles (1890) Photochemical Investigations and a New Method of Determination of the Sensitiveness of Photographic Plates, J. Soc. Chem. Ind. May 31, 1890.
- ^ a b "KODAK PROFESSIONAL TRI-X 400 Film / 400TX". http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.jhtml.
- ^ a b Stuart B. Palmer and Mircea S. Rogalski (1996). Advanced University Physics. Taylor & Francis. ISBN 2884490655. http://books.google.com/books?id=TF6Igz5lJLgC&pg=PA349&dq=hurter-driffield-curve+h-d-curve&lr=&as_brr=3&ei=songR5KAJIWusgOWlPQU&sig=FgC6_uAklssPUpNaUyyr2lS0hNk.
- ^ Kenneth W. Busch and Marianna A. Busch (1990). Multielement Detection Systems for Spectrochemical Analysis. Wiley-Interscience. ISBN 0471819743. http://books.google.com/books?id=9H0W1J-Rku4C&pg=PA339&dq=h-d-curve+density&lr=&as_brr=3&ei=qYzgR46lBYbosQOrzpgV&sig=_kTikTsCw2-7B8XvfO6y73rmTkc#PPA341,M1.
- ^ Richard R. Carlton, Arlene McKenna Adler (2000). Principles of Radiographic Imaging: An Art and a Science. Thomson Delmar Learning. ISBN 0766813002. http://books.google.com/books?id=oA-eBHsapX8C&pg=PA318&dq=h%26d-curve+density&lr=&as_brr=3&ei=to3gR5GCLI6eswOs98kV&sig=s_vE4f5PMysrrCtgM7_HJrsRu_Y.
- ^ Ravi P. Gupta (2003). Remote Sensing Geology. Springer. ISBN 3540431853. http://books.google.com/books?id=74T8X1zqgF4C&pg=PA62&dq=d-log-e-curve+density&lr=&as_brr=3&ei=eY7gR4qWEILusgO60YCrAg&sig=MBImrU6KwlZwoV29Xl1PywwEINQ.
- ^ Leslie D. Stroebel and Richard D. Zakia (1993). The Focal Encyclopedia of Photography. Focal Press. ISBN 0240514173. http://books.google.com/books?id=CU7-2ZLGFpYC&pg=PA794&dq=d-log-h-curve+density&lr=&as_brr=3&ei=BI_gR6qIGIiUtgOY5tEV&sig=wfoH3l-C-AKifDLLObbnYn7FrHg.
External links
- Basic Sensitometry And Characteristics of Film (Kodak undated)[1]
- A memorial volume containing an account of the photographic researches of Ferdinand Hurter & Vero C. Driffield ; being a reprint of their published papers, together with a history of their early work and a bibliography of later work on the same subject. (Royal Photographic Society of Great Britain 1920)
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