Control of intensity and colour temperature of a photographic flash lamp

摘要

The intensities of illumination of flash discharge lamps ST1, ST2 can be adjusted by intensity controls 13, 13a respectively, which select which elements of capacitor banks C10-C17 and C10'-C17' are discharged through the lamps. The illumination intensity can be adjusted without affecting the colour temperature. A colour temperature control 14 operates to connect a selected one of resistors R11 to R19 in circuit, whereby the charging voltage of the capacitor banks can be varied. Charging voltage may be increased stepwise from 300 volts to 620 volts, which may give a corresponding stepwise increase in colour temperature from 5400{K to 5800{K. A third lamp ST3 is connected through diodes D15a, D15b to both capacitor banks, so that the intensity of the lamp ST3 is the sum of the intensities set by respective rotary switches R/S, R/S1 associated with the two capacitor banks. Digital displays DG1, DG2, DG3 indicate the intensities of the lamps ST1, ST2, ST3 respectively. Switches R/S and R/S1 allow the intensities of lamps ST1 and ST2 to be adjusted independently of one another; one lamp can thus be used as a main light and the other as an auxiliary light. Modelling lamps M1, M2, M3 are connected to the cathodes of respective lamps ST1, ST2, ST3 and indicate the intensity of the illumination of the flash lamps prior to taking a photograph. The capacitor banks are charged from an AC mains supply via a voltage multiplying rectifier 1 which is automatically switched from a voltage doubling mode for 220 volts AC input, to a quadrupling mode for 110 volts AC input.