DE3139806A1 - Process for the automatic control of the flash energy of an electronic flash system - Google Patents

Abstract

A photographic camera is connected with an electronic flash system. It exhibits an automatic exposure system as well as at least one photoelectric receiver system which measures the object brightness and which is disposed in one of the image planes of the camera lens or is situated opposite one of these planes. For the automatic control of the electronic flash system, an electrical signal corresponding to the emitted energy of a preliminary flash is stored and used in a computation circuit for determining the required main flash energy. For the purpose of the determination of the flash energy required for a perfect exposure prior to the triggering of the camera shutter and for the purpose of the generation of a preliminary flash with the lowest possible expenditure of energy and non-disturbing brightness, for the generation of the memory signal a) electrical signals are formed from the measured and stored surrounding light intensity (object brightness) as well as from the measurement of the increasing energy of the preliminary flash arriving at the photoelectric receiver system, b) these measurement signals are constantly compared with one another and c) from this comparison 1. a predetermined ratio between the surrounding light intensity and the preliminary flash energy arriving at the photoelectric receiver system is formed, 2. the preliminary flash is shut off on reaching this ratio and 3. the magnitude of the emitted preliminary flash energy is determined. d

Description

Process for the automatic control of the flash energy

an electronic flash The invention relates to a method for automatic control of the flash energy of an electronic flash connected to a photographic camera is connected, which has an automatic exposure and at least one in the image plane of the camera lens or one in one of these conjugate planes located or facing these photoelectric receiver system for Has measurement of the object brightness, in which one of the emitted energy of a Pre-flash corresponding electrical signal is stored and in a computing circuit is used to determine the main lightning energy required.

In such methods, the aim is to increase by measuring the am on Object reflected energy of a pre-flash which is necessary for a technically perfect exposure required energy of the main flash can be determined Devices for automatic flash control are well known. she serve to dose the amount of light generated by the synchronous opening of the camera shutter ignited flash is emitted. Usually this is done during the Flash 1 ichtausradiation light reflected from the object measured, the Integrated measured value and the transmission interrupted as soon as the integrated measured value corresponds to the amount of light required for optimal film exposure.

The disadvantage of these measurements is the much greater consideration the objects to be imaged that are closer to the light source.

It is also, for example, from DE-PS 21 27 876 and 24 16 137 as well the DE-OS 23 11 528 and 23 46 46 known, the one with the opening of the camera shutter A pre-flash is sent ahead of the synchronously ignited flash, which is used for the test illumination of the subject and measured the amount of light reflected on the subject and is saved. The main flash is controlled via a proportionality signal, which from a comparison of the stored value with one from the main flash based measured value is derived.

The emissions of pre-flash and main flash occur with these arrangements with the release of the calendar lockO U.S. Patent 3,709,123 a flash device is described in which the pre-flash before film exposure, So before the camera shutter is released, the main flash is ignited, as before is described, controlled. For the definition of the pre-flashing energy the parameters influencing the exposure, such as object distance, aperture, Filter indeces etc. are taken into account.

From DE-OS 23 47 618 it is also known for automatic Control of one with a photographic camera with electrical light intensity evaluation associated electronic flash, the evaluation of the light reflected on the object by integrating an electrical signal generated with this light during a time to be made by the light intensity evaluation of the photographic Camera is set.

The disadvantage of this method is the high level of circuitry Effort as well as the high energy consumption for the pre-flash.

In DE-OS 24 OS 188, finally, a method for automatic Describes the emission of an adjustable amount of light during flash-synchronized photography, at which the time of the pre-flash emission is determined so that the time difference between the pre-light emission and the main light emission within a period of time during which the remaining image or waiting picture of the eye is preserved, and that the film even after the Vorlichtemission by a Closure member is kept hidden.

The difficulty of such a procedure lies in the need to Adjust the shutter sequence and the main light emission extremely precisely to one another have to.

The known methods and arrangements have the common disadvantage that the flash energy required for a technically perfect film exposure can only be determined after the ignition of the main flash and that the use of a Pre-flash requires a relatively high expenditure of energy.

The invention is therefore based on the task of a method for indicate automatic control of an electronic flash, with which the technical A flawless film exposure required flash energy before triggering the camera shutter takes place and in which a pre-flash with the lowest possible energy expenditure and is generated with non-disturbing brightness.

The solution to the problem for a method of the type mentioned at the beginning succeeds in that to generate the memory signal a) from the measured and stored ambient light intensity (object brightness) as well as from the measurement of the am photoelectric receiver system incoming, rising energy of the pre-flash electrical signals are formed, b) these measurement signals are constant are compared with one another, and c) from this comparison 1. a predetermined ratio between ambient light intensity and the pre-flash energy arriving at the photoelectric receiver system established, 2. the pre-flash is switched off when this ratio is reached and 3. the amount of pre-flash energy determined is determined.

It is of course possible to use the stored pre-flash energy to be saved once for several recordings, so that the recordings are always the same Exposure or a deliberately fluctuating exposure (variation) (series exposures).

Advantageous further developments of the method according to the invention are Subject of the subclaims.

In the drawing, the invention is shown schematically in exemplary embodiments shown.

The figures show: FIG. 1 a circuit arrangement for implementing the invention Method, FIG. 2 a relationship diagram between ambient light intensity and pre-flash energy, FIG. 3 shows a course diagram of the pre-lightning and main lightning according to the invention, FIG Diagram of the voltage required for pre-flash and main flash, FIG. 5 shows a circuit arrangement according to FIG. 1 with an additional diaphragm area display. FIG. 6 shows a circuit arrangement with reference measuring circuit and with warning display for over- or. Underexposure, Fig. 7 shows a shutter blocking circuit; FIG. 8 shows a circuit arrangement with a reference measuring circuit and the measurement combination of ambient light intensity and main flash, Fig. 9 circuit arrangement for adjusting the comparison stage controlling the preliminary flash according to FIGS Fig. 10 shows a block diagram for the combination of at least two electronic flash units.

The circuit arrangement shown in Fig. 1 in a not with The photographic camera shown contains a ambient light intensity measuring Measuring circuit 1 consisting of a photodiode 2, one of these downstream amplifiers 3 and a resistor 6 located in the feedback branch with switch 7 and a capacitor arranged in another feedback branch of the amplifier 3 4 with switch 5 consists.

Another measuring circuit 8 is included, which consists of a photodiode 9, an amplifier 10 and one connected in the feedback branch of this amplifier Capacitor 11 is formed with switch 12. The electrical signal it generates is fed to an input 13a of a final comparison stage 13.

The signal emerging from the measuring circuit 1 is transmitted via a z, ener-J) iode 14 and a resistor 16b fed to an operational amplifier 15, to its A current is added to the summation point via a resistor 16a, which comes from a Constant voltage Uk arises, which for example from the camera power supply is branched off.

The constant voltage Uk is dimensioned so that the output voltage U is only slightly greater than the voltage value op output by the Mel3 circuit 1. she has a change in the ambient light intensity shown in Fig. 2 curve shown. After that, the pre-flash energy even decreases in the range I <I1 not or only a little too. The diagram shows that the range I1 <I < I2 is a linear range.

The output voltage of the operational amplifier 15 is on the one hand at the other input 13b of the first comparison stage 13 and on the other hand at one input 17a of a second comparison stage 17. The other input 17b of the comparison stage 17 receives the output signal of a computer 18, which in addition to a computer 19 is present. The latter is fed from a memory 20 with a delete key 21. The memory 20 is preceded by a timer unit 22 with a start button 23 which when switched on, outputs a voltage U that increases linearly with time.

z This voltage U is on the one hand the memory 20 and z on the other hand fed to an input 24b of a third comparison stage 24. The other entrance 24a of the comparison stage 24 is at the output of the computer 19.

The circuit arrangement contains a switch 25 for switchability the automatic flash to operation with and without pre-flash.

The arrangement described so far for the automatic control of the The flash energy of an electronic flash works as described below: Intended to the electronic flash can be operated like conventionally without a pre-flash, the switch becomes 25 brought into the position shown in dashed lines. One not shown here Potentiometer, for example, flows a voltage analogous to a film speed to an input of the comparison stage 13. When the camera is triggered and the Image window through the first locking process of the not shown here Camera, the switch 12 in the measuring circuit 8 is opened and the flash is ignited. That of the object to be photographed in a known manner on the photodiode 9 of Measuring circuit 8 reflected light is converted by this ifl a voltage that is passed on to the amplifier 10 and the capacitor 11 charges. The voltage at the output of the amplifier 10 is the comparison stage 13 via its input 13a s guided. If this voltage reaches a potentiometer (not shown) set and located at the input 13b, a measure for the necessary film exposure corresponding size, then the comparison stage 13 responds and switches the flash away.

It is known to the person skilled in the art that the response threshold of the first Comparison stage 13 can also be permanently set. Then this is done by the photodiode 9 generated electrical signal initially logarithmized and with the film speed offset. The resulting signal is delogarithmized. The resulting Electricity is being integrated.

Before the pre-flash is triggered, switch 5 and switch are open 7 closed. At the output of the op-amp 3 is a voltage that is a measure for the ambient light intensity. At the output of the op-amp 15 there is a voltage which, taking into account the constant voltage Uk and the Zener diode 14, is a measure for the ambient light intensity.

When operating the electronic flash with pre-flash, the switch is on 25 initially in the position shown by dashed lines. The switch 12, through the closing of which the capacitor 11 is discharged is at the beginning of the pre-flash opened. Before that, the switch 7 is opened in the measuring circuit l, so that the Signal nal for the ambient light intensity is stored.

When the pre-flash is triggered, its reflected light is as above described, converted by the photodiode 9 into a current that is passed by the capacitor 11 is integrated so that the corresponding voltage is fed to the input 13a of the comparison stage 13 is supplied. The response threshold of the comparison stage 13 is very low. It is determined by a voltage Uop at the output of the operational amplifier 15 from the voltage derived by the measuring circuit 1 from the ambient light intensity u of the constant voltage Uk taking into account the Zener diode 14 arises.

After what has been described so far, it is easy to see that as well as the profile diagram in FIG. 3 and the voltage diagram in FIG. 4 show in comparison In addition to the main flash, there is only a very short and low-energy pre-flash.

At the same time as the start of the pre-flash, the start button is also activated 23 open. The timer unit 22 then gives the linearly increasing over time Voltage U ab, which, as already described above, is fed to the z memory 20.

If the first comparison stage 13 is equal, it speaks to his Inputs 13a and 13b voltage from the measuring circuits 1 and 8, see above the pre-flash is switched off. The currently pending voltage value is also used U held by the memory 20 and the computer 19 calculates various exposure parameters (e.g. film speed ° DIN, aperture diameter B1) and others for exposure essential information (e.g. integral or selective measurement I / S, lightning amplitude Am) with the stored voltage U.

z The one required for technically perfect image exposure The main lightning energy (duration or amplitude) is output by the computer 19 as a voltage. This is fed to the third comparison stage 24 via its input 24a.

After the pre-flash, the switch 25 is drawn in the drawn Position brought.

With the first shutter curtain that opens when the shutter is released the start button 23 is opened again, the same as in the above-described storage process closed and the main flash fired 0 The timer unit 22 is playing a voltage U abs that rises linearly with time is that of the third comparison stage 24 is led to M via the input 24b. If this voltage reaches that of the computer 19, the comparison stage 24 responds and switches the main flash away. Before the next flash exposure, the memory 20 is cleared by pressing the delete key 21 deleted again.

In the area 1> I2 of the relationship diagram in FIG. 2, the preliminary flash can and the main flash will be blocked.

This happens when the from the measuring circuit l and the constant voltage Uk resulting voltage value Uop is greater than a voltage Uv1, which results from offsetting the exposure parameters, such as

B. Film speed or aperture, with a minimum exposure time, such as B. 1/30 sec., In the first computer 18 results. With switches 5 and open closed switch 7 then speaks to the second comparison stage 17, at which first input 17a the sum voltage U and at the second input l7b that of the Op first computer 18 output voltage Uv1 is. If both tensions are equal Uop and Uv1 switches the Comparison stage 17 both pre-flash and also main flash off.

However, it is also possible that the pre-flash energy as a function of the ambient light intensity is different, z. B. after a root function, The The circuit arrangement shown in FIG. 5 is expanded to include a diaphragm area display. It essentially corresponds to that shown in FIG. 1 and works in principle like these. Only the Zener diode 14, the operational amplifier 15, the resistors 16a, b, c, and the constant voltage Uk have been combined in a switching block 26.

The circuit arrangement described in FIG. 1 is expanded from display diodes 27, 28 connected to the computer 19a, a diaphragm plate 29, a slide or rotary potentiometer 30 and a switch 31.

In the position of the switch 31 shown in dashed lines is the Diaphragm plate 29 connected directly to the potentiometer 30, on which one of a diaphragm opening proportional voltage is adjustable. The aperture stop is in the extended position 29 connected to the computer 19a, the one corresponding to a central aperture Voltage size to the diaphragm plate 29 emits. This middle aperture can according to a geometrical message from the largest and smallest possible Aperture or by other optimization, in addition, the calculator gives 19s via the display diodes 27 and 28, values for the largest or smallest possible Aperture opening for the shortest or longest flash duration.

It is possible that the triggering of the main flash is blocked if the calculated target energy could not yet be achieved, because z. Bo the lightning capacitor is not yet fully charged. FIG. 6 shows the circuit arrangements described so far expanded by a reference measuring circuit 32. It comprises a reference photodiode 33, an amplifier 34 and one connected to the feedback branch of this amplifier Capacitor 35, which via a manually or automatically operated switch 36 can be discharged.

A poor electronic flash device 37 is located to ignite the preliminary flash Switch 38 closed0 At the same time, the switches 36 in the reference measuring circuit 32 and the switch 12 in the measuring circuit 8 is open. The one from the electronic flash unit 37 emitted pre-flash energy is applied to both the photodiode 9 and the Reference diode 33. These convert the energy reflected from the object into a current, which is integrated with the amplifiers 10 and 34 in the capacitors 11 and 35 respectively will.

Before the preliminary flash, as described above, the measuring circuit 1 measures the Ambient light intensity. As also described above, it gives rise to tension from which, together with a constant voltage Uk added in the switching block 26 as the threshold value at the input 13b of the comparison stage 13 is.

If the pre-flash energy generated by the measuring circuit 8 is reached, at the input 13a voltage the size of the threshold value, then switches the Comparison stage 13 starts the pre-flash. With this switching process, that of the reference circuit 32 output voltage value is held in memory 20 and the calculation of this Value in the computer 19 is set in motion with the parameters mentioned above.

On the basis of this offsetting, the search gives 19c a voltage value which corresponds to an exact flash exposure. This tension is over the input 39b is fed to a comparator 39.

When the camera shutter (not shown here) is triggered, with the opening of the first locking process by actuating a switch 40 the main flash ignited on the electronic flash unit 37. The reference measuring circuit converts its energy 32 into a voltage which is fed to the comparator 39 via its input 39a will. If the voltages from computer 19 9 and reference measuring circuit 32 are equal the comparator 39 switches off the main flash.

Light-emitting diodes 40, 41 fed by the computer 19c give before the recording an ad that is in front of an over- or underexposure that may be expected warns.

But it is also possible with the circuit arrangement indicated in FIG. 6 if over- or

Underexposure to block the camera shutter.

This is effected according to FIG. 7 by a transistor 42 which Via protective resistors 43 or 44 into the computer 19 and the light-emitting diodes 40 or 41 connecting branches is laid. Another in front of the transistor 42 lying resistor 45 protect this against overload when energized from a not shown with energy source. Before recording, the transistor is over the resistors 45 and 47 conductive, so that the holding magnets, not shown here the shutter curtains are energized and hold them in the 'tGeschlossen "position. If the computer 19 outputs information that an exact film exposure is possible is, the resistors 43 and 44 are de-energized. The lock holding magnets can fall off after the trigger 46 is closed. The closure can expire. Gives the computer 19 but a voltage corresponding to an overexposure or underexposure off, the transistor 42 remains conductive via the resistors 43 and 44, when the camera release, which is indicated here by a switch 46, is actuated has been.

The circuit arrangement shown in FIG. 8 is a simplified variant the arrangement according to FIG. 6 insofar as a measuring circuit 49 is included with which measures both the light energy and the pre-flash. It includes one Photodiode 50, an amplifier. 51, one in the first feedback branch of the amplifier 51 lying resistor 52 with switch 53, one in the second feedback branch laid capacitor 54 with switch 55 and one arranged in a third branch Switch 56.

The circuit arrangement is opposite to that shown in FIG a further memory 57 with memory key 58 expanded. The computer 19b is on connected to the time generator 59 of the camera. The functional sequence is as follows: When the switch 53 is closed and the switch 56 is open, the measuring circuit 49 measured the light energy. The resulting voltage value becomes the Memory 57 supplied and held there by pressing the memory button 56. So then the switches 53 are opened and 55 closed. The ignition of the Vorelitz takes place by closing the switch 38 on the electronic flash 37. Then at the same time the switches 36 of the reference measuring circuit 32 and 56 of the measuring switches 49 open. The measurement of the pre-flash energy emitted by the electronic flash device 37 and their shutdown takes place as described for FIG. 6. The resulting Voltage is fed to memory 20. The 20 20th or 57 recorded voltage values are forwarded to the computers 18 and 19b, respectively2 where they deal with exposure parameters such as film speed ° DIN, aperture diameter Bl, the information I / s, whether it was measured integrally or selectively, and further, Correction values that emphasize or suppress certain recording characteristics K are further processed. In particular, the shutter opening time can be adjusted by means of correction values can be influenced via the time images 59, which makes it possible to To expose parts of the image through the ambient light and other parts, e.g. B. the foreground, illuminated by the flash. The ratio of ambient lighting to flash lighting can still be varied by changing the correction values.

When the main flash is triggered by closing switch 40 on The computer 19b then does not control the electronic flash unit 59 of the time generator Zarge placed camera, while the computer 18 applied a voltage to the input 39b of the Comparator 39 sets. If this voltage is different from that by the reference circuit 32 he generated and reached the voltage present at the input 39a, the comparator switches 39 fire the main flash. It goes without saying that both the computer 18 as also to the computer 19b, as already shown in FIG. 6 Deschrleo ben, as a warning flashing Diodes can be connected.

To increase the pre-flash either more or less than the surrounding light, can e.g. B. the threshold of the comparison stage 13 can be made adjustable. Is to the circuit arrangement of FIG. 8, as shown in FIG. 9, to one of one Current source 60 fed by means of a switch 61 in the branch between Memory 57 and comparison stage 13 switchable slide resistor 62 expanded.

However, it is entirely conceivable for the person skilled in the art that the computer 18 8 can be programmed in such a way that a flash exposure is brought about which is, for example, two levels above the ambient light.

In this case, the ambient light is regarded as an interference threshold and not used for exposure.

But it is also possible that the ambient light - we z. B.

in a photo studio - formed by several electronic flash units will. The memory 20 according to FIGS. 6 - Q can be provided twice, so that on the one hand "ambient light" and on the other hand that of the foreground or the main picture reflected and converted into a voltage energy is stored. After offsetting of the stored values with the other known exposure parameters as described above During the main recording, ambient light is then applied to the eventual output of warning messages and foreground or main image part lighting emitted for different lengths of time.

In Fig. 10 is a block diagram for such a combination with at least two electronic flash units shown. The reference number is 63 denotes a first assembly, which is an electronic flash device 37 and the measuring circuits 1 and 8 according to FIGS. 1 and 5, and by a switch 64 in operation set, for example, the main part of the picture to be recorded lights up.

The reference numerals 32-36 identify the reference measuring circuit according to FIG FIGS. 6 and 8.

A second assembly 66 which can be actuated by means of a switch 65 is included also an electronic flash unit 37 and the measuring circuits according to FIGS. 1 and 5 1 and 8. It is used, for example, to illuminate the foreground.

In one with the two assemblies 63 and G6 as well as the reference measuring circuit 32 connected third assembly 67 are the Bailgruppc 13, the comparator 39, two Memory 20 and computers 18 and 19 contain, which the exposure parameters - such as aperture, film speed - and the information about the mode of exposure measurement - integral or selective (I / s) - are supplied for the purpose of accounting and those with Displays 68, 69 for warning of under- or overexposure and / or for display a diaphragm area can be connected.

Claims (17)

Claims 1. A method for the automatic control of the ßlltzenergie an electronic flash connected to a photographic camera, which an automatic exposure system and at least one in the image plane of the camera lens or one located in one of these conjugate planes or one opposite them having photoelectric receiver system for measuring the brightness of the object an electrical signal corresponding to the emitted energy of a pre-flash stored and in a computing circuit to determine the required main lightning energy is utilized, characterized in that to generate the memory signal a) from the measured and stored ambient light intensity (object brightness) and from the Measurement of the rising ones arriving at the photoelectric receiver system Energy of the pre-flash electrical signals are formed, b) these measurement signals are constantly compared with one another and c) from this comparison 1) a predetermined one Relationship between ambient light intensity and incoming light at the photoelectric receiver system Pre-flash energy produced, 2) the pre-flash when this ratio is reached switched off and 3) the amount of pre-flash energy emitted is determined and stored will. 2 The method according to claim 1, characterized in that the to be specified Relationship between ambient light intensity and pre-flash energy as a function of the Ambient light intensity is determined. 3 The method according to claim 1, characterized in that the computing circuit also from other exposure parameters (such as time, aperture, film sensitivity) obtained electrical signals are supplied. 4. The method according to claim 1, characterized in that from the The recorded pre-flash energy derives a signal warning of incorrect exposures will. 5. The method according to claim 1, characterized in that from the recorded pre-flash energy a signal indicating the possible aperture range is derived. 6. The method according to claim 1 and 3, characterized in that the the electrical signal derived from the pre-flash energy received in interaction with the camera's automatic exposure for automatic control of the aperture of the lens is being used 7. The method according to claim 1, characterized in that that the electrical signal derived from the recorded pre-flash energy for Control of exposure parameters is used for continuous shooting. 8. The method according to claim 1, characterized in that one off The signal derived from the ambient light intensity controls the flow of energy to the pre-flash. 9, method according to claim 1, characterized in that an off The signal derived from the recorded pre-flash energy determines the flow of energy to the main flash controls. 10, the method according to claim 9, characterized in that the from derived from the absorbed pre-flash energy Target energy signal of the main lightning whose energy supply blocks until it is full Energy development required storage energy is fully achieved again. 11. The method according to claims 1 and 3, characterized in that that an output signal of the computing circuit is used for display purposes. 12. The method according to claims 1 and 3, characterized in that that an output signal of the computing circuit for controlling exposure parameters used for continuous shooting. 13. The method according to claim 1, characterized in that the signals the ambient light intelligence as well as the pre-flash energy absorbed by selective Measurements are obtained. 14. The method according to claim 1, characterized in that in addition those derived from the ambient light intensity or the recorded pre-flash energy electrical signals are stored separately. 15. The method according to claims 1 and 14, characterized in that that in cooperation with the automatic exposure from the Umlichtincensität- as well the pre-flash energy signal in the computing circuit determines the optimal aperture will. 16. The method according to claims 1 and 14, characterized in that that for the control of the main flash energy either more ambient light intensity or more pre-flash energy is used. 17. The method according to claims 1 to 16, characterized in that that a main flash energy is generated in order to ensure the color temperature, which is at least one exposure level above which results from the ambient light intensity and the ambient light intensity resulting from the camera shutter time.