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452 ABSTRACTS
graphing the object through a screen of very narrow transparent vertical lines while the camera is moved in an arc around the object, at the same time moving the plate horizontally the width of the lines. When the picture is shown a line screen is placed in front and the two views give an appearance of depth. — Kodak Abstr. Bull.
Measure of the Effective Luminosity of Objectives. J. HRDLICKA. PhotoRevue, 41, Sept. 1, 1929, p. 267. A simple method is described for finding the effective relative aperture of photographic objectives, by taking into consideration the loss of illumination through reflection and absorption in the lens. An objective rated at //4.5 is found to have an effective aperture of only //5.54.— • Kodak Abstr. Bull
Lens Viewing Angles. J. DUBRAY. Internal. Phot., 1, September, 1929, p. 14. Formulas are given which enable the cinematographer to make a rapid calculation of the width of object space embraced by lenses of different focal lengths for both sound and silent apertures. C. M. T.
Distribution of Light Flux from a Mirror Arc. H. NAUMANN. Filmtechnik, 5, Aug. 31, 1929, p. 389. The author uses a photographic method to examine the intensity distribution from a mirror arc. The effects of changing arc current or its position with respect to the mirror and of altering the size of the projection objective are illustrated by silhouette photographs. Serious disturbance of the illumination of the film aperture may result from poor adjustment of the arc and reflector. C. M. T.
Color and Its Measurement. J. GUILD. Phot. J., January, 1930, p. 22. The paper deals with the question of applying a standard system of measurement to the color of objective things. Though we can apply physical measurements to the properties of the stimulus of vision, we cannot evaluate the sensation of brightness or that of color. The author discusses Young's trichromatic theory, then studies the effects of visual conditions on color measurement, explaining why the National Physical Laboratory recommends the use in all color measuring apparatus of a field subtending an angle of 2 degrees. With an angle of this size measurement is not affected by the brightness of the field or the adaptation and fatigue of the1 eye. Standardization of color measurements is more easily effected in the case of additive colorimeters, several of which are described. For standardization of measurement, it is recommended that color measurements be expressed on the trichromatic system. The standardization of the illuminant and the method of illumination are then discussed, as well as the question of the "normal eye" and the problem of correcting the observer's eye by means of auxiliary filters. G. L. C.
Dental Profession Uses Motion Pictures. Intern. Phot. Bull., February, 1930. No less than ten reports made at the 66th Meeting and Clinic of the Chicago Dental Society were illustrated with 16 mm. motion pictures, one of them showing the physiology of mastication made entirely by Dr. Hugh McMillan. G. L. C.