The Underwater Camera Calibrator is a precision instrument that provides a known angular array of collimator targets to be photographed by a camera under test. The images of the targets are then read and measured to yield the necessary data for the determination of focal length, location of principal point, distortion, and resolution. Generally, the targets of a camera calibration instrument are located at optical infinity; however, the images presented to the camera by the Underwater Camera Calibrator may be set for any distance from 6 feet to infinity. Underwater cameras are tested with the tank filled with water and regular cameras are tested without water in the tank.

The variety in the spectral sensitivities of photoreceptive materials in current use today requires close control of the spectral transmittance of lenses for proper systems design. A device utilizing second order narrow band interference filters is described in which the spectral transmittance of compound lenses can be quickly and accurately determined, at a series of discrete wavelengths, by a relatively unskilled operator through a semi-automatic push-button operation.

A study into the stability of the photographic latent image is presented. Four factors have been investigated - time, temperature, humidity, and spectral sensitization of the emulsion. It is found that the effective speed of the emulsion passes through a maximum and then begins a rapid decrease when the material is stored at elevated temperatures. This study shows humidity and sensitization to be less in magnitude than temperature in producing changes in the latent image when all are a function of time.

Today, vast numbers of researchers, technicians, teachers, students and laymen are being exposed to radiation from a wide variety of lasers. The nature of some of the photobiological mechanisms which are responsible for tissue damage are discussed briefly. Laser radiation parameters which influence the degree of danger to ocular tissues are indicated and threshold values are given. The difference between establishing safety criteria and suggesting safety procedures is defined. A brief account of some of the problems that must be solved before safety criteria can be estalished is given and current safety procedures are discussed.

This report discusses concepts, symbols, units and nomenclature for describing the transmission of radiant flux through earth's variable density atmosphere. The geometrical concepts used in the field of photometry and radiometry are the same. A common set of symbols is proposed for use in both fields together with some terms not previously used.