The purpose of this thesis is to study the effects on the shape and position of the characteristic curve due to a low level uniform exposure to white light. This was accomplished using a special camera which produced an image of a neutral density -wedge on a film strip. One half of this image was covered while the other half was uniformly exposed to a low level light exposure. In some cases the low level exposure was first applied to half of the film strip with the image exposure occurring second. The density differences between the two halves of the film strip were measured and compared to density differences expected from additive exposure. The density differences were also analysed with respect to the time delay between the imaging and additional uniform exposure. This is repeated for each level of additional exposure. A graphical analysis based on a hypothetical film type was performed and then the same done for the test data. Graphical analysis was then done to determine if effects other than those attributable to additive exposure occurred. Conclusions were drawn concerning the effects of the level of additional exposure, and of the time delay between exposures, on the density differences produced by the additional exposure. For the film type and processing conditions used, a level of additional exposure producing a density of 0.016 above base plus fog density, introduced significantly greater density increase when the additional uniform exposure occurred after the image exposure. No significant difference, with respect to time, occurred for an additional exposure of 0.006 above base fog. The greatest effects were noticed in the toe region of the density versus Log exposure curve, where the slope of the density versus exposure curve is the greatest. For the type 5302 film, non-uniform exposure in the camera system caused errors in determining the log exposure values for the projected step wedge image. Sensitometer control strips were used to determine those values for the type 5302 film, however, no control strips existed for the Tri-X, due to my error, and exposure values could not be determined. At a 90% confidence level, no significant density differences could be ascertained other than those due to additive exposure.

Library of Congress Subject Headings

Photography--Exposure; Photography--Processing

Publication Date


Document Type


Department, Program, or Center

School of Photographic Arts and Sciences (CIAS)


Carroll, Burt


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