相反則感光計に関する研究 [II] 相反則感光計4種について

In this paper, the present state of four kinds of reciprocity sensitometers is reviewed, which have been improved in the Research Laboratory of Fuji Photo Film Co., Ltd.<BR>Long exposure time reciprocity sensitometer:<BR>The exposures are timed by a double falling type shutter which is operated electromagnetically. The time signal is given by areocise putmatic timer for second order, and by push-button operated manually with a stopwatch or an electro-magnetic pendulum clock for longer exposures than 16 seconds. The methods of varying the intensity are:(1) exchanging from one source tungsten lamp into another, (2) inserting into optical path a neutral opal glass of optical density value of 2 and a set of stops which varies the effective source area, and (3) shifting a light source on the optical bench over the range from one meter to ten meters. Thus exposure intensity covers the range from 10^-4 to 600 lux.<BR>Deci-second reciprocity sensitometer:<BR>The exposure is timed by a rotating sector with four-steps slot which is uniformly illuminated by a condenser. This slot light source is imaged on the film by a relay camera lens with magnified scale. By proper selection of the steps, exposure time can be varied over the range from 1 to 1/64th second. An auxiliary rotatiug secter with a wide slot revolves at a slower speed than the main sector. Thus exposures are given every 40 seconds repeatedly for continuous work. Step-wise variation of illumination is accomplished by a set of chronium-foiled neutral filters or by irises of relay camera lens. Thus exposure intensity can be varied from 20 to 2000 lux<BR>Milli-second reciprocity sensitometer:<BR>A strip of film is attached on the pendulum. A relay camera lens forms an image of the slit light source on the film. A series of slits are used, the widths of which are six kinds from 1 to 20 millimeters. Two kinds of relay camera lenses are used, the magnifications of which are 1: 1 and 1: 1/10. The exposures are timed by a pendulum with a film traversing the optical path at a constant speed. The periods of pendulum are stepwisely 1.68 and 4.49 seconds. Thus exposure time can be varied over the range from 64 to 0.1 milliseconds, and exposure intensity from 1500 to 10⁵ lux.<BR>Micro-second reciprocity sensitometer:<BR>A strip of film is wrapped around the outside surface of a drum. A relay camera lens forms a reduced image of a micro-slit light source on the film. The slit widths are changed over the range from 1 to 10 millimeters. The reduced scale of the relay camera lens is 1: 1/10. The exposure time is determined by the linear speed of the film and the width of the slit image on the film.<BR>The rotation speed of the drum is varied stepwisely over the range from 31.2 to 500r. p. m. Thus exposure time can be varied over the range from 100 to 1 micro-seconds, and the exposure intensity from 10⁵ to 10⁷ lux. As a light source a high brightness Xenon lamp is used. The speed of rotating durm is controlled and calibrated by JJY standard radio wave. An auxiliary lens shutter which operates under the combination with revolution of the drum is used to prevent double exposure.