DE3003661A1 - CIRCUIT ARRANGEMENT FOR EXPOSURE CONTROL - Google Patents

Description

Circuit arrangement for exposure control

The invention relates to a circuit arrangement for operating lighting control of photographic cameras®

In cameras with automatic diaphragm control, it is known that the lens diaphragm is closed after a measuring phase according to a value calculated in the camera. However, due to errors in the aperture setting, the previously calculated aperture value is not reached exactly 56 602) _o

It is also known to have cameras with a memory puncture equip, according to which determined exposure values are initially stored and at certain recording times can be queried for exposure control «

Circuit arrangements of the first type take into account the current luminous flux that passes through the lens in a desired manner when the working aperture measurement takes place immediately before the exposure Recordings in which, for example, in the interest of an exact exposure of the main subject of a scene to be recorded, an object measurement is first carried out and the on «= but would take place from a changed location, However, the known circuits are not suitable »At

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the known cameras with memory function is an advantageous work aperture measurement to compensate for the aperture setting error not possible"

The invention is intended to increase the puncture versatility of photographic cameras

The object of the invention is to create a circuit arrangement for regulating the exposure of photographic cameras, which has a memory function and / or an override input despite a light measurement taking place immediately before the exposure guaranteed

According to the invention, this object is achieved in that an optionally switchable electronic memory circuit The signed information content is used when the camera is triggered with the counter reading can be superimposed on an exposure control circuit.

The invention is explained below on the basis of an illustrated embodiment «

An input circuit 1 with a photo receiver 2 is a control amplifier 3 and a sequence control circuit 4 subordinate. The latter is available with a working register 5, a memory circuit 6, an aperture value memory 7 » an exposure time memory 8 and an aperture control circuit 9 in connection. With a 10 the sequence of an objective diaphragm 11 blocking electromagnet is referred to. A D / A-V / andler 12 is fed back to the control amplifier 3, which is controlled by the working register 5. The memory circuits 6, 7, 8 are provided with a decoder 13 connected, which forms the control unit for a digital display 14. At 15 there is a driver stage for one Shutter control magnets 16 designated, 17 and 18 are with-

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Switches that can be operated by means of two camera buttons. The mode of action is as follows:

During an object light measurement taking place with an open aperture, 4 pulses are written into the working register 5 and into the aperture memory 7 and the exposure time memory 8 via the sequence control circuit containing a clock generator, according to the prevailing object luminance, the pilm sensitivity and a preselected preferred exposure time, until the in the working register 5 reported the pulse train written in via the D / A converter 12 to the control amplifier 3 and thus the control loop is calibrated. When the calibration is achieved, the pulse train emanating from the sequence control circuit is terminated. The information contained in the aperture value memory 7 and the exposure time memory 8 from z. B ₀ k = 5.6 and t = ¹ / s are visualized by means of the digital display 14 125th

Now increases in size after pressing the memory button 17 on the camera and, consequently, now effective memory circuit 6 on the Poto receiver incident light amount by z. B. 2 light levels (2 L), the information in the memory 7 and 8 is not changed »Such light flux changes are for example possible if the final location of the photo after taking an object measurement for backlit photos taken and a repeated measurement is carried out from this due to the camera. The occurred The light current change of + 2 L is controlled by the sequence control 4 written into the memory circuit 6. If you press the camera shutter button further, the ob-

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BATH ORIGINAL

lens aperture 11 to close under spring force. At the same time, the working register is detuned in accordance with the value written into the diaphragm value memory 7. As soon as the associated control loop detuning is compensated for by the reduction in the illuminance on the photoreceiver 2, the electromagnet 10 is de-energized and the shutter closing process is stopped. This is the aperture with a. Setting errors of z. B. - ^1/4 Level in the above-shown V / ert set. During the subsequent working aperture measurement, pulses are fed into the working register 5 and an exposure time is specified here which corresponds to the changed light conditions and takes into account the aperture setting errors:

^1/125 s - 2 L + 1/4 L

When the information stored in the memory circuit 6 is called up, the information written into the working register 5 is Exposure time back to the value

^1/125 3 - 2 L + ^1/4 I + I 2 = ^1/125 s + ¹ / 4L

corrected. The final exposure time therefore corresponds to that determined at the time of storage and is corrected for the aperture setting error. After this time has elapsed, the sequence of the trailing closure member to ZV. The shutter control magnet 16 blocking this point in time is de-energized via the driver stage 15 and the exposure is ended. When the exposure is ended, the memory circuit 6 is reset to its starting position.

The discovery was made above using a camera automatic aperture adjustment described. Of course, it is not limited to such cameras but is also with cameras with manual

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Aperture preselection and light-dependent exposure time formation applicable, also for cameras with automatic program for aperture and exposure time,

Occasionally, shots with intentional under or overexposure are desirable. The circuit according to the invention is also suitable for this. The information content up to + 2 L stored in the memory circuit 6 via the sequence control 4 is called up after the camera is triggered and is used to change the correct exposure time resulting from the aperture measurement Digital display 14 made visible for control. The memory content of the memory circuit 6 is automatically deleted at BeIichtungsbeendigung _#

Instead of this opto-electrical override input can A manual incorrect exposure setting can also be made via the switch 18 take place «. For this purpose, a on the camera further button of the switch 18 is closed once or several times and each time it closes A signed override signal is gradually written into the memory circuit 6. When the camera is triggered the Spe ichereinhalt is superimposed on that of the working register 5, so that in turn a corrected exposure time results

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BATH ORIGINAL

R e r s e

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Claims (8)

Expectations : 1. Circuit arrangement for exposure control photographic Cameras with automatic exposure adjustment according to those of a computational posture during exposure values determined in a measuring phase, characterized in that an optionally switchable electronic memory circuit (6) is used, the signed information content of Camera triggering can be overlaid with the counter reading of an exposure control circuit (5) » Circuit arrangement according to Claim 1, characterized in that that the memory circuit as an object luminance prevailing at certain recording times storing circuit is designed 3ο circuit arrangement according to claim 1, characterized in that that a working register (5) controlled by a clock generator of a sequence control circuit (4) as an actuator for an automatic aperture setting according to an aperture value calculated during the measuring phase and as a counting circuit for exposure time formation is formed, which results on the basis of a light measurement with a working aperture, one current exposure time corresponding counter reading the information content is also fed to the memory circuit 4. Circuit arrangement according to claim 1, characterized in that that the memory circuit as an override Bingabeschaltung is designed, the memory content of which is automatically deleted when the exposure is terminated 030 045/0 53S 5. Circuit arrangement according to claim 4, characterized in that the memory circuit as an opto-electrical controllable override input circuit is formed. 6ο circuit arrangement according to claim 4, characterized in that that the signal value determining the respective override input by means of a push button switch (18) is controllable 7 · Circuit arrangement according to Claims 1 to 6, characterized in that the information content of the memory circuit can be recognized by means of a digital display (14) visible in the camera viewfinder. 8. The circuit arrangement according to claim 1, characterized in that the memory circuit, a resolution of ¹ / 8th exposure level has _o 03004 5/0583