Abstract: Lamp operating voltage levels are reduced by using a boost circuit to initiate a triggering sequence in one of two lamps connected in series. The boost circuit is connected across one of the lamps at a connector point common to the two lamps. In a preferred embodiment, trigger pulses are applied sequentially to each lamp, the boost circuit voltage contained in an associated capacitor is discharged through the first triggered lamp, causing it to begin conduction. Most of the voltage from a main storage capacitor then becomes available to break down the second lamp.

Abstract: An auto-flash photographing system includes a flash lamp unit, a photometry unit for detecting light reflecting from a subject of interest, a reference setting unit, a comparator, and a trigger unit. The flash lamp is once triggered to emit a flash, and the light detected by the photometry unit is compared with a reference value defined by the reference setting unit by the comparator. If the detected light is lower than the reference value, it indicates underexposure so that the trigger unit once again triggers the flash lamp. In this manner, the flash lamp is fired more than once while a shutter is set in a fully open condition until an optimal exposure condition is attained. In another structure, a plurality of flash lamps are provided they may be fired at the same time and extinguished separately or they may be fired one after another in sequence until a desired exposure condition for phototaking is obtained.

Abstract: A heavy duty flasher for incandescent lamps for a motor coach or the like incorporates a pair of power MOSFETs in parallel for efficient, cool operation and includes a pair of timers, one for flash rate control and the other for producing AC for operating a voltage multiplier to provide gate voltage for the MOSFETs. Protective circuitry senses current overload and terminates current flow to protect the power devices while allowing inrush current to the lamps at the beginning of each cycle. A circuit sensitive to the presence of load supplies power to the timers only under load conditions.

Abstract: In a flash photographing apparatus, a flash device is arranged to slow the rise of flashing characteristic thereof at the initial stage of flashing. To attain this purpose, the electric charge of a first capacitor is impressed via an inductance onto a flash tube at the initial stage of flashing. Following this, the electric charge of a second capacitor is directly impressed on the flash tube without passing through the inductance.

Abstract: The illumination device includes a charging part, an energy storage device, a flash tube and an amplitude control device, by means of which the energy storage device can be charged to different voltages. A time control device is superposed upon the amplitude control device. In consequence of the two control devices, the flash tube emits light with a predetermined color temperature as a function of the set amplitude and of the set flash duration. The color temperature can thereby be influenced in a controlled manner, with the maintenance of a very fine setting of the quantity of light, and can also be maintained constant independent of the quantity of light emitted.

Abstract: Electronic flash equipment in the present including a Field Effect Transistor which is connected to a flash tube in series and a voltage control structure which controls the conductivity of the Field Effect Transistor by control of a voltage across the gate and the source of the Field Effect Transistor. A automatic light control and a high frequency repeating flash light radiation are realized by control of the voltage.

Abstract: There is disclosed a high light level cutoff apparatus for use with night vision devices. The apparatus employs a digital method of timing implemented by a divider counter responsive to a crystal controlled input frequency which essentially controls a latch to produce an automatic shutoff of a night vision device during high light ambient conditions which conditions would undesirably reduce the effective life of such a night vision device. The circuitry disclosed utilizes a digital method of clocking and employs the latching relay as indicated which is operated by the digital counter. The circuitry provides a feed back from the latching relay which resets the night vision system so that it will re-operate if a transient accidentally serves to operate the goggles while the light level is in a high state.

Abstract: An electric lamp for the photopolymerization of dental materials is supplied with constant electric power so that constant light output is obtained. The control circuit used to this end operates with a triac (3) connected between an a.c. voltage supply (2) and the lamp (1), said triac being controlled by signal values stored in a read-only memory of a microprocessor (4). Said stored values are respectively allocated to pairs of instantaneous values of lamp current and lamp voltage, the instantaneous values being detected in each cycle of the a.c. supply voltage and being utilized to address the read-only memory.

Abstract: A close-range lighting flash device comprising an electronic flash unit including a plurality of xenon tubes, an illuminator unit provided integrally in the flash unit and including a plurality of illuminator lamps, a light-transmitting panel arranged in front of both of the xenon tubes and the illuminator lamps, and a control device for energizing the illuminator unit. The light-transmitting panel has first and second portions aligned respectively with the xenon tubes and the illuminator lamps, the second portions having a light diffusing density smaller than that of the first portions.

Abstract: A control circuit for a photoflash gun capable of fast recycling times, including a flashtube (FT), a switching circuit (SW, L1) for initiating operation of the flashtube, a switch (CR1) in series with the flashtube and switched on at the same time as the flashtube to permit current flow through it, and an arrangement for resetting the switch (CR1) after a predetermined time to cut off current flow through the flashtube. The arrangement comprises an inductance (L2) and a capacitor (C2) coupled to the anode of the switch (CR1), so that when the flashtube is switched on, current discharges through the capacitor (C2), creating a back EMF in the inductance (L2). A voltage of negative polarity is thus developed across capacitor (C2) to switch off switch (CR1) after a predetermined time, thereby to switch off the flashtube. The switch off time is controlled by a light calculation circuit responsive to ambient light.

Abstract: A high-intensity discharge (HID) metal vapor lamp and starting apparatus includes a metal vapor lamp having an outer envelope containing a gas filled arc tube, the fill gas including xenon, the arc tube having a pair of spaced electrodes with a starting aid surrounding the arc tube intermediate the electrodes, a non-linear dielectric element shunting the spaced electrodes and a ballast means and an electrical conductor coupling the spaced electrodes to a base member connected to a low voltage source whereby starting of the metal vapor lamp from a low voltage source is effected.

Abstract: An overvoltage protection circuit limits the output voltage of a DC to DC converter to a maximum desired output voltage. An output voltage sensing circuit includes a semiconductor device such as a sidac having a normal resistive region of operation as well as a negative resistance region of operation which begins at a breakover voltage and extends into a foldback region. One terminal of the sidac is coupled to sense the converter output voltage while the second terminal opposite end of the sidac is coupled to a biasing device in the form of a resistor which generates an overvoltage signal when the sidac conducts current. The overvoltage signal from the biasing resistor is coupled to a converter switching transistor disabling circuit which reduces the converter output voltage to a level below the maximum desired output voltage in response to the overvoltage signal.

Abstract: A lamp illumination adjusting apparatus for automobiles comprises a reference triangular wave generator, an adjusting voltage setting circuit, a comparator to compare the reference triangular signal with the adjusting voltage and to output comparison signal, a driver circuit including a MOS field effect transistor which is controlled directly by the comparison signal, and a lamp which is connected in series to the driver circuit and interposed between a power source terminal and the ground.

Abstract: An apparatus for flash photography being of the type in which for one shot a number of different flash tubes are time-serially fired and the amount of flash light emitted from each flash tube is controlled in accordance with a respective arbitrarily chosen individual value independently of the others.In the above-described arrangement, one and the same comparator is sufficient for controlling the firing operation of all the flash tubes, thereby giving an advantage of simplifying the construction of the apparatus.

Abstract: Voltage regulating circuitry maintains a load voltage of a DC to DC converter within a prescribed range. For that purpose, an SCR latching switch is connected to conduct upon the load voltage increasing to a predetermined upper level, and to become non-conductive in response to the load voltage decaying from the upper level to a predetermined lower level. Bistable switching circuitry, connected to an output of the SCR switch, serves as a current source in response to the SCR conducting, and as a current sink in response to the SCR latch becoming non-conductive. The bistable circuitry provides "snap action" control of an output transistor, which is coupled to the converter, when its load voltage rises and falls, respectively, to the upper and lower levels of the prescribed range, so that the voltage regulating circuitry has a stable, well defined hysteresis.

Abstract: A device for boosting power supply voltage is provided with a transformer having a secondary winding which generates an elevated voltage when the power supply current is supplied to the primary winding, whereby the voltage generated in the secondary winding is supplied to a load while voltages corresponding to the inverse electromotive force generated in the primary winding are supplied to another load.

Abstract: An electric circuit arrangement for use in energising a flash tube (3) to provide a series of pairs of flashes, each pair consisting of a main flash and a rapidly following second flash, includes first and second capacitors (C9, C10) which are controlled to effect discharge of first only the first capacitor (C9) and then both the first and second capacitors (C9, C10) across the flash tube (3), cyclically, to provide the two flashes of each pair, in series. By varying the relative values of the first and second capacitors (C9, C10) the time interval between the flashes of each pair can be varied. All flashes produced can have the same peak intensity while the flashes in each pair can have different energy contents.

Abstract: A panoramic light emitter of an omnidirectional horizontal light beam with very sharp cut-off in the vertical plane is disclosed. The sharp cut-off prevents interference near airports. High average powers are attainable because the light source can be distributed rather than be a point source. The omnidirectional-in-the-horizontal-plane light emitter with a high degree of vertical beam control is achieved by combining a generally cylindrical refractor with an internally emitting open-ended generally conical light source. The internal emitting surface of the conical light source is in the focal plane of the cylindrical refractor. The refractor sharply images the source with its edges, and that image is projected panoramically as the light beam having sharp cut-off at the edges of the image. The external surface of the conical light source does not emit, thus preventing undesired angles of light from passing out through the refractor.

Abstract: A laser flash lamp triggering circuit is connected in parallel with the flash lamp and between the flash lamp and the flash lamp power supply. A impedance element is connected between the parallel trigger circuit network and the pulse forming network in the power supply. The impedance element preferably in the form of a saturable reactor has a high impedance to the high voltage trigger pulse and a low impedance to the current flow from the storage capacitor forming part of the pulse forming network. This invention relates to a laser flash lamp power supply and, more particularly, a triggering circuit for the flash lamp which has low power dissipation.

Abstract: A pulse generating apparatus includes a base current supply section for generating a constant DC current having a first prescribed current level for turning on a xenon lamp, and a pulse current section for adding a pulse current having a second current level greater than the first current level and a prescribed pulse duration within a prescribed repetition period to the constant DC current. The base current supply section and pulse current section should satisfy the following equations:1.4.ltoreq.Imax/Imini.ltoreq.60.2.ltoreq.t/T.ltoreq.0.7T.ltoreq.1/40Where Imax is the sum of the first and the second prescribed current levels, Imini is the first prescribed current level, T is the prescribed repetition period, and t is the prescribed pulse duration.When the pulse current added to the DC current is supplied to a xenon lamp, the xenon lamp outputs a strong light during the pulse duration of the pulse current, and a feeble light during the absence of the pulse current.

Abstract: An apparatus for conducting flash photographing by a camera capable of incorporating or setting therein a flashlight device and generating a trigger signal at full opening of a shutter, and a capacitor adapted to release electric charge stored therein in response to said trigger signal for a flash discharge tube to emit flash.

Abstract: An improved high power (40,000 watt) high intensity arc discharge power supply which provides reliable, automatic ignition control and enables precise variation of lamp power in dual AC and DC modes of operation over an extended dynamic range from 400 watts to 40,000 watts. A capacitive boost circuit is provided to supply the high voltage necessary to ignite the lamp. Upon start-up, the voltage on a boost circuit capacitor is monitored by an ignition circuit which automatically enables the ignitor when the voltage is at the required level and switches the ignitor off when the lamp starts. After ignition the boost charging circuit is disabled and the power supply operates in a normal mode. The power supply operates on a three phase alternating voltage input through a three phase bridge, switches it through a drive transistor and then supplies it to an inductor. The signal is then supplied through an H-bridge commutator to the boost circuit, the ignitor and the arc lamp itself.

Abstract: An electronic flash device fires one or a pair of flash tube sequentially for continuous shooting photography with a motor driven photographic camera, for substantially continuous illumination or for sequential illuminations at intervals, as well as fire the flash tube a single time for one shot photography. The flash device is provided with a main capacitor and an auxiliary capacitor which selectively energize the flash tube or tubes. The auxiliary capacitor is charged by the main capacitor and discharged to energize the flash tube for a small amount of flash light and short-time restoration of the flash firing circuit. When a pair of flash tubes are employed, they are alternatively actuated for the sequential firing and one of them is actuated for the single time firing. The pair of flash tubes are coupled with each other through a commutation capacitor and switch elements for quick repetition of their firings.

Abstract: The operation of a strobe lighting system is electronically monitored from a remote location to verify proper operation of all of the individual elements of the system. A current sensor is coupled in series with the flow of current between the strobe power supply and the strobe lamp and generates a voltage pulse in response to each flash inducing pulse of current through the strobe lamp. A remote indicator is coupled to the current sensor and generates a humanly perceptible output signal (visual or audible) in response to the voltage pulse from the current sensor. The strobe flash monitor enables a strobe lighting system user to continuously monitor system operation without direct observation of the strobe lamp flashes.

Abstract: An electric flash device for photography is controlled of its light radiation of a flash tube by a transistor, which is connected in series with the flash tube and is given its base current through a parallelly connected capacitor and resistor, and when the transistor turns OFF, an electric charge stored in the capacitor is applied across the base and the emitter of the transistor as a reverse bias.

Abstract: In a flash photographing system including a camera having a light output control circuit for producing a stop of light emission signal when a light intensity of an illumination light reflected by an object reaches a predetermined level and a start circuit to start activation of the light output control circuit in response to a start of light emission signal, and a flash device electrically connected to the camera and having a flash bulb for emitting the illumination light, the flash device comprises detection means for detecting electrical connection with the camera, start of light emission signal generating means responsive to the detection means for supplying the start of light emission signal to the start circuit of the camera in synchronism with the emission of the illumination light by the flash bulb, and light emission stop means for stopping the emission of the illumination light by the flash bulb in response to the stop of light emission signal from the light output control circuit of the camera.

Abstract: A toy light sword including a hollow blade with a fluorescent coating on the inside, or it may be translucent and tend to glow when illuminated. A stroboscopic lamp unit is discharged by a switch to provide a burst of high intensity light and a glow on the sword blade. An inertial switch is provided in the blade in one optional embodiment whereby the high-intensity light is discharged when the sword is moved against an object to indicate that contact has been made. Also, a sound generator can be provided to emit a sound when the burst of light occurs. An exemplary circuit for use with the light sword is also part of the invention.

Abstract: An electronic flash includes a main capacitor having a discharge loop in which a circuit arrangement including a flash discharge tube, a switching element and an emission controlling capacitor is connected. During the time the flash discharge tube is maintained excited, the emission controlling capacitor is either charged or discharged to cause an emission of flashlight from the flash discharge tube.

Abstract: In an electronic flash apparatus which is provided with a first discharge tube for bounce illumination and a second flash discharge tube for direct illumination, emission of flash light by the first flash discharge tube and emission of flash light by the second are arranged to separately begin and to simultaneously end to simplify complex circuit arrangement otherwise required for having the amount of light reflected by the object of flash light emission by the first discharge tube and that of flash light emission by the second discharge tube in a fixed ratio. The second discharge tube is arranged to flash without fail despite of the simplified circuit arrangement.

Abstract: The enclosed electronic flash device for a camera includes a booster circuit connectible to an electrical power source or battery, a high voltage rectifier diode for rectifying the output of the booster circuit, and a storage capacitor. A main power supply switch and an auxiliary power supply switch are connected in series between the negative poles of the power source and capacitor. The auxiliary power supply switch is arranged to close when the flash device is attached to the camera. A signal terminal is connected to the negative pole of the storage capacitor through other circuit elements and another signal terminal is connected to one contact of the auxiliary power supply switch, which is connected in turn to the negative pole of the storage capacitor. The auxiliary power supply switch is connected in series with the main power supply switch at a point farther from the negative terminal of the battery than the main power supply switch.

Abstract: An amplification factor selection circuit for an automatic light emission control circuit which enables selection of an amplification factor in accordance with an F-value, comprises a flash bulb for emitting a flash light to an object, a photo-sensor for sensing a light reflected from the object, an amplifier for amplifying the photo-current of the photosensor, a capacitor for starting charging upon emission of the flash light, a semiconductor device for controlling a charging current of the capacitor in accordance with an output of the amplifier, a light emission suppress circuit for suppressing the light emission when the capacitor is charged up to a predetermined level. A first reference voltage applied to the input terminal of the amplifier and a second reference voltage applied to the output of the transistor are relatively controlled. Two constant current sources are connected to opposite ends of a resistor and a point on the resistor is clamped to a predetermined potential.

Abstract: Driving device for illuminating lamp of flash apparatus comprises means for detecting supplied voltage supplied to the illuminating lamp and generating a detection signal corresponding to thus detected voltage, power supply means for supplying power to the illuminating lamp according to the supplied voltage, and means for controlling the period of power supply from the power supply means to the illuminating lamp according to the detection signal.

Abstract: A flashlight emission apparatus is provided which inhibits the emission of flashlight from a flash discharge tube before a voltage to which a main discharge capacitor is charged reaches a proper voltage level for emission. This occurs in response to an output from a detector that detects the voltage across the main capacitor. The apparatus provides an indication that the main capacitor is being charged as long as the converter is in operation to provide a booster action, and terminates the indication and ceases the operation of the converter when the voltage across the main capacitor reaches a proper voltage level for emission.

Abstract: An electronic flash apparatus for flash photographing comprises flash discharge means, means for supplying a voltage to the flash discharge means, first light emission control means comprising first trigger means for triggering the flash discharge means to cause a discharge therein, for the purpose of the flash photographing and second light emission control means. The second light emission control means comprises oscillator means for generating periodic output signals, second trigger means for periodically triggering the flash discharge means in response to the periodic output signals thereby periodically initiating the discharge in the flash discharge means, detecting mean for generating an output signal upon detection of the initiation of the discharge in the flash discharge means and means for terminating the discharge in the flash discharge means in response to the output signal of the detecting means.

Abstract: An electronic flash of series controlled type is provided. It comprises a series connection of a flash discharge tube and a main thyristor, which series connection is further connected in series with a thyristor which forms a reverse charging path for a commutating capacitor. The series combination of the flash discharge tube, the main thyristor and the last mentioned thyristor is connected in parallel with a main capacitor. A diode is connected in series with the commutating capacitor so that their series combination is in parallel with the reverse charging thyristor. The reverse charging thyristor is rendered conductive as the main thyristor is rendered conductive so as to establish a reverse charging path for the commutating capacitor therethrough when a commutating operation is to be performed. This prevents a reverse charging current to the commutating capacitor from passing through the flash discharge tube, thus enabling an accurate control over the amount of exposure produced by flashlight.

Abstract: The disclosed flash device is of the kind that incorporates an integrated processing circuit requiring a stable voltage, but one and the same battery supplies both a booster circuit and the processing circuit. The device avoids the drop in voltage to the processing circuit when the booster circuit draws current after a flash by means of a detector circuit that detects the flash or the operation of the booster circuit. A switching circuit responds to the output of the detector circuit and supplies the charge on a back-up capacitor to the integrated processing circuit. Thus, in the event of a flash, the processing circuit which is normally operated by power from the battery is protected from a supply voltage drop by the supply of a voltage from the back-up capacitor.

Abstract: A highly efficient circuit for converting a low level DC voltage to the high voltage necessary for energizing a flash lamp. The circuit is very small and non-complex, it is portable and is quickly recharged, particularly being adaptable for emergency flash uses and for toys such as light swords and laser pistols. A very efficient portion of the circuit, comprising a DC/AC inverter, an AC/DC converter and a voltage multiplier, operating at an appropriate frequency, enables the flash capacitor to always be maintained substantially at peak voltage value with minimum power usage.

Abstract: A power supply unit for electronic flash includes a converter drive circuit which is activated when a main switch is turned on or in response to the completion of a shutter operation or the completion of a film winding operation, thereby driving a converter for oscillation. The converter charges a main discharge capacitor to a given voltage, and when the given voltage is reached, the converter drive circuit is deactivated, thereby automatically ceasing the oscillation of the converter.

Abstract: An electronic flash including a discharge flash tube controlled by a first switch and a commutation capacitor for controlling the first switch. There is provided a second switch for governing the operation of the commutation switch. A charging circuit is provided for charging the commutation capacitor and includes a resistor connecting the commutation capacitor with an electric power source. The resistor has a resistance value which is small enough to allow a current not smaller than a current at which the second switch is turned off.

Abstract: An electronic flash device fires one or a pair of flash tubes sequentially for continuous shooting photography with a motor driven photographic camera, for substantially continuous illumination or for sequential illuminations at intervals, as well as fire the flash tube a single time for one shot photography. The flash device is provided with a main capacitor and an auxiliary capacitor which selectively energize the flash tube or tubes. The auxiliary capacitor is charged by the main capacitor and discharged to energize the flash tube for a small amount of flash light and shorttime restoration of the flash firing circuit. When a pair of flash tubes are employed, they are alternatively actuated for the sequential firing and one of them is actuated for the single time firing. The pair of flash tubes are coupled with each other through a commutation capacitor and switch elements for quick repetition of their firings.

Abstract: An automatic electronic flash measures brightness of a predetermined photographing angle including a photographic object, and using the measured brightness and film sensitivity indicates a stop value to be set in camera when the photographic scenery has rear light, and the automatic electronic flash operation is automatically lowered by the extent of F-stop value (automatic F-stop value) of 1-2 EV than the indicated stop value, thereby satisfactory automatic fill-in photographing with the automatic electronic flash can be made; and the automatic electronic flash further comprises means to warn when the brightness of the photographic scenery changes from the measured value, and besides, the above-mentioned controlling corresponding to the automatic F-stop value is examined taking account of the scenery brightness and film sensitivity and produce another warning when automatic F-stop value is an impractical value.

Abstract: An excitation circuit for an electronic flash device for a photographic camera is arranged to energize the flashtube in a plurality of successive steps for each shot. In each of the successive steps, the flashtube is energized only for a time interval which is shorter than the time interval required by the flashtube to operate at its full power. This keeps the proportion of infrared radiation to a minimum.

Abstract: A series controlled electronic flash of automatic emission control type includes a switching element connected in series with a commutating switching element for selectively charging a commutation capacitor. A trigger signal is repeatedly applied to a main switching element, the commutating switching element and the charging switching element in a given sequence to enable a continued emission at substantially constant brightness level to be obtained from a flash discharge tube. A trigger capacitor may be connected with pair of switching elements for charging and discharging the trigger capacitor. A trigger signal may be repeatedly applied to the pair of switching elements for charging and discharging the trigger capacitor, to the main switching element, to the commutating switching element and the commutation capacitor charging switching element in a given sequence, thereby allowing a multiple emission to be obtained intermittently and at a high rate from the flash discharge tube.

Abstract: An electronic flash unit for emitting flashlight toward an object to be photographed in order that a camera may obtain proper exposure comprises flash means having a flash tube which emits flashlight, means for driving the flash tube in order that the flash tube may emit flashlight, and means for applying light to the interior of the flash tube prior to the driving means causing the flash tube to emit flashlight.

Abstract: An exposure light source device wherein a control circuit 1 controls a light source for emitting pulse lights, with respect to the member of light emissions and the amount of light emitted at each time. The light source device is particularly useful for color additive type photographic color enlarger. When the device is used in such an enlarger, the number of light emission and each emitted light amount is determined such that the exposure time is approximately the same regardless of the total amount of exposure.

Abstract: An energy-saving electronic flash unit for a rapid sequence of flash exposures includes status indicator apparatus operable for signaling the readiness of the flash unit for the next flash in the sequence as a function of the flash energy expended to produce the previous flash. When the energy retained by a flash-firing capacitor at the termination of the preceding flash exceeds the energy expended in producing that flash, energy-monitoring circuitry causes a status indicator device to signal that the flash unit is sufficiently charged for the next exposure in the sequence.

Abstract: A power supply unit for electronic flash includes a plurality of charging units connected to a main capacitor of an electronic flash through diodes which prevent a reverse current flow. Each charging unit includes a d.c. source and a booster converter. An efficient utilization of the source battery is attained by reducing loading upon each source. The use of components of reduced capacity enables a reduction in the size of the overall unit. A single power switch enables a simultaneous initiation of the charging of the main capacitor by all of the charging units. When the main capacitor is charged to a given value, disable means are simultaneously operated in response to an output from charging voltage detecting means, thus simultaneously ceasing the charging operation of the charging units.

Abstract: Disclosed is a power supply control device which automatically cuts off power to a flash apparatus by turning off a power switch a predetermined time after the switch is turned on to prevent waste of electrical energy arising from careless failure to turn off the power switch. The power supply control device is provided with a timer circuit which sets the predetermined period of time and is arbitrarily resetable with a manually operable power switch.

Abstract: A power supply system comprising an a.c. voltage source (ACS), a load (LL) and a detachable (DCC) cable connection (CC). In order to prevent a dangerously high a.c. voltage from occurring between cable conductors (CC1, CC2) when the cable connection is loose, a safety circuit (CITSR) is provided which includes an on/off switching circuit (S1, SR1, S2, SR2). The safety circuit (CITSR) includes a parallel arrangement (CI) of at least one capacitor (C) and a direct current source (I). The parallel arrangement (CI) is part of a direct current circuit (CC2, DC2, CC1, S1, DC1, CC2) which is closed via the cable conductors (CC1, CC2), the a.c. voltage source (ACS) and the load (LL). The parallel arrangement (CI) is coupled to the on/off switching circuit (S1, SR1, S2, SR2) via a threshold circuit (TC). When a controllable a.c.

Abstract: The disclosure is directed to an improved light measuring device which is used in flash photography for measuring a preliminary flash light to obtain camera exposure informations for photography under a primary flash light. The device is so arranged as to preliminarily obtain information of light amount contributing to photographing, with respect to each portion or area of a scene to be photographed or object field, in taking photographs with the employment of the auxiliary light.