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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.

A Kodak Model 101 sensitometer has been improved from the original design and also been made more versatile so as to be able to expose a greater variety of general-purpose films. Improving the machine has been accomplished by modifying the shutter to produce an exposure time of 1/20 second instead of 1/5 second, thus eliminating reciprocity law failure from calculations, and also complying with the American National Standards Institute specification for exposing continuous -tone films. The previous tungsten lamp has been replaced with a tungsten-halogen lamp. Versatility has been added to the machine by introducing a xenon-flash lamp in the existing lamphouse. Simplicity in operation has been maintained, considering that either system uses the same button for making exposures. One additional control for selecting either source has been added. Both systems perform with 2% repeatability and 2% uniformity across the exposing surface. A system accuracy of + 5% is assigned.

A research project was designed to repair and optimize the performance of a. prototype Ansco Model 4 Microdensitometer which had been inoperative for several years. Repairs were made in the start circuit of the control panel, lamp voltage control and the 2nd cut-in potentiometer to make the instrument operative. Calibrations and alignments were made and an apparatus was designed and implemented to facilitate lateral slit alignment. The original objective of optimization was not met due to insufficient time but the instrument was made operative and accurate to less than 2% over the 0-3.0 density range and 15% above 3.0. Recommendations have been made within the project report whose implementation would further improve the performance of the instrument. It was strongly recommended that this project be continued as another senior research project during the next academic year.

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