possessing a different spectral reflectivity in white light, which is a necessary condition for the appearance of graininess to occur. Also, the mean diameter of film crystals becomes a significant factor when deciding on a diameter for a scanning digitizer's entrance aperture. A six micron diameter aperture was used here which was approximately 1/2 mean crystal diameter of the present film.

The roll of exposed Kodak film was developed commercially. According to the photographer, a normal processing delay occurred (approximately 1.5 weeks). She did not specify that special development or any enlargements were desired. A set of color positive prints ("jumbo size") and the developed color negatives cut apart into sets of two frames were received by the photographer on or about October 26, 1981. Inspection of the attached second frame to the one in question by the author showed that it was of a child standing inside a home. This child was the daughter of the couple who owned the camera; the scene was confirmed to have been taken inside their home in Campbell River, British Columbia. This fact agreed with the story told by the couple concerning the sequence of events of their automobile trip to the north end of Vancouver Island and return and the photographs they remembered taking.

It was not until the couple had received the set of color prints from the Vancouver processing laboratory that they noticed the strange aerial disc in the clear blue sky near the mountain top.

Image Analysis Results

The analysis of the negative (and also first generation positive black and white and color prints) included the following steps: (a) linear and angular measurements, (b) micro-densitometry scans to establish optical density range, (c) black and white photographic enlargements using papers having different spectral sensitivities, and (d) computer-based contrast enhancements.

Linear and Angular Image Measurements. Selected linear measurements of the disc's image on the enlarged print are given earlier (cf. The Photograph and Negative). The angular measurements shown in Figure 3 were determined on the basis of the linear measurements of the image, the camera lens' focal length, and on-site survey which is described below. Referring to Figure 3 it may be pointed out that the photograph's center was elevated about nine degrees arc above the horizontal and the tip of the mountain was very close to the geometric center of the photograph. The disc subtended 1.3 degrees arc. Elevation angles from the local horizontal were measured with a surveyor's transit to the top of the mountain, the location of the photographer, and the sun. These latter measurements were obtained at the same time of day, day of the year, and location as that of the original photograph but two years later. These results are presented in Figure 4 with the disc shown in side view. The exact outline of the disc is not known; also, the dome-like protruberance is not shown here.