Patent GB-1487021-A (GB)
Title: Cinecamera capable of automatic time exposure
IPC: G03B17/42
Filed: 1975-01-22
Abstract: 1487021 Cinematographic cameras NIPPON KOGAKU KK 22 Jan 1975 [25 Jan 1974] 2827/75 Headings G2A and G2E In a cinematographic camera, generally of the type described in Specification 1487022, means are provided for setting the exposure time beforehand. The circuit shown in Fig. 1 is the same as that described in Specification 1487022, except that switches 80, 81, 84 and variable resistors 82, 83 are added. Switch 80 has three positions and is moved to correspond with switch 12. Switch 81 has a contact 81a moveable between fixed contacts 81a, 81b by means of a cam (86) mounted on the shaft (22) carrying the shutter, Fig. 2 (not shown). When switches 12, 81 are turned to contacts 12a, 80a, switches 81, 84 and the variable resistances are out of circuit and the apparatus operates to provide a series of exposures as long as the button B is depressed, as described in Specification 1487022. When switches 12, 80 are on contacts 12b, 80b and switch 84 is open, the apparatus operates as described in Specification 1487022 in this mode. If switch 84 is closed manually, capacitor 1 is charged through the variable resistor 83, and the setting of that resistor determines the time at which transistors 6, 8 again conduct, which in turn determines the time during which the shutter is closed, as long as button B remains depressed. When switches 12, 80 are on contacts 12c, 80c, the condenser 2 may be charged either through variable resistor 83 or by variable resistor 82, according to the position of the shaft-operated switch 81. Accordingly, the setting of variable resistor 83 determines the time between exposures, and the setting of variable resistor 82 determines the time during which the shutter is closed, as long as button B remains depressed. Second embodiment, Fig. 8 (not shown). The emitter of transistor 8 is connected to resistors (88), (89) connected in series with diodes (87) across the power supply 1. Proper choice of component values renders the exposure time, and the interval between exposures, independent of supply voltage variations and of ambient temperature. The capacitor 15 is replaced by a capacitor (40) which, when switch 14 is closed and switch 4 is open, discharges through series resistors (41), (42). The junction of these resistors to the base of a transistor (43) with the holding coil 16 connected in its emitter-collector path. Thus coil 16 is energized while capacitor (40) discharges. By choosing high values for resistors (41), (42), the capacitance (40) is made less than the capacitance 15. Third embodiment, Fig. 9 (not shown). Capacitor 2 is charged through a constant-current transistor, and the circuit allows the separate coils 10, 16 to be replaced by a single coil (10'). Fourth embodiment, Fig. 10 (not shown). Variable resistor 82 is replaced by a photo-electric cell (110). A filter or stop (111) is used to allow for film speed or objective lens aperture. Transistors 6, 8 are repalced by a SCR (62) and a switch (61), operated by a cam on shaft 22, controls the SCR and discharges capacitor 2. Fifth embodiment, Fig. 13 (not shown). An exposure-determining variable resistor 82 may be switched into circuit alternatively with the photoelectric cell (110). A variable resistor (89') connected between the emitter of transistor 8 and the negative line enables compensation to be made for film speed or diaphragm aperture.