In the evaluation of conventional photographic imaging systems the non-linearity of the macroscopic curve can easily be dealt with by examining the "effective exposure" rather than expressing the density or transmittance. Dealing with the nonlinearities on a microscopic level, however, is very difficult since they result from development adjacency effects. A tool was made using a "V-shaped" groove design by G.W. Schumann which consists of a series of microscopic linear density wedges. The density wedges were made by filling V-cut grooves in a high quality acrylic plastic with a carbon-epoxy dispersion. The density wedges have been produced at the frequencies of 0.98. cy/mm and 0.57 cy/mm. These wedges have effective diffuse density ranges between 0.21 and 1.18. Their density gradient has been varied from .28 to 2.58 density units per mm. The wedges were then tested for their practicality for use in image evaluation. It was found that the characteristic curve for a small image area with a low surrounding density is higher in contrast and shifted to a higher speed when compared to a conventionally produced curve. When the micro scale density wedges were imaged with a high surrounding density, the results were not significantly different from those obtained with the conventional step wedge. There are several drawbacks attributed to the V-groove design that are discussed. The results from the practical application tests, however, suggest that there is significant merit for the micro scale wedges for use in the study of chemical adjacency effects. The micro-scale continuous density wedges are found to present a new concept to sensitometry where the characteristic curve can be related to some of the adjacency effects encountered in specific applications.
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Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Mattison, Lawrence and Triplett, Roger, "Production of a Micro-Scale Linear Density Wedge" (1978). Thesis. Rochester Institute of Technology. Accessed from
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