DD143184A1 - CIRCUIT ARRANGEMENT FOR EXPOSURE CONTROL - Google Patents

Abstract

The invention relates to a circuit arrangement for exposure control of photographic cameras. The aim and object of the invention is to increase the functionality versatility of cameras by providing a circuit arrangement which ensures a memory function and / or an override input despite a light measurement taking place immediately before the recording. In accordance with the invention, an optionally switchable electronic memory circuit is used, the signed information content of which can be superimposed on the counter reading of an exposure control circuit when the camera is triggered.

Description

Title of the invention:

Circuit arrangement for exposure control

Field of application of the invention; ;

The invention relates to a circuit arrangement for exposure control of photographic cameras.

Characteristic of the known technical solutions:

In cameras with automatic iris control, it is known that the lens shutter after a measurement phase according to a value calculated in the camera is closed *. Due to aperture setting errors, however, the previously calculated aperture value is not exactly reached. In order to compensate for the resulting exposure error, the light reaching the measuring receiver after the aperture setting is measured and a slight correction of the exposure time stored during the measuring phase is carried out (DE-AS 22 56 602),

Furthermore, it is known to equip cameras with a memory puncture, according to which determined exposure values are initially stored and can be interrogated at certain recording times for the exposure control »

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Circuit arrangements of the first type do indeed take into account the current luminous flux which passes through the objective during the working diaphragm measurement which takes place directly before the recording, in a desired manner. Recordings in which z. B. in the interest of an accurate exposure of the main subject of a scene to be recorded first an object measurement is performed and the recording but is done from a different location, the known circuits are not suitable. In the known cameras with memory function is an advantageous Arbeitsblendeessung to compensate for the Blenseinst ellfehlers not possible.

Object of the invention

The invention is intended to increase the functional versatility of photographic cameras.

Essence of the invention

The object of the invention is to provide a circuit arrangement for the exposure control of photographic cameras, which ensures a memory function and / or an override input despite a light measurement taking place immediately before the recording.

According to the invention, this object is achieved in that an optional turn-on electronic memory circuit application is used, the signed information content in camera triggering with the count of an exposure control circuit is superimposed.

embodiment

The invention will be explained with reference to an illustrated embodiment below *

An input circuit 1 with a photoreceiver 2 is a control amplifier 3 and a sequence control circuit 4 downstream. The latter is connected to 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 combination. With 10 a the expiration of a lens shutter Tl blocking solenoid is called. On the control amplifier 3, a D / A-Y / andler 12 is fed back, which is controlled by the working register 5. The memory circuits 6, 7 »8 are connected to a decoder which forms the drive unit for a digital display 14. 15, a driver stage for a shutter control solenoid 16 is designated. 17 and 18 are actuated by two camera buttons switch.

The mode of action is the following:

During an object-light measurement taking place at an open aperture, impulses are written into the working register 5 as well as into the aperture value memory 7 and the exposure time memory 8 in accordance with the prevailing object luminance, the film sensitivity and a preselected preferred exposure time via the sequence control circuit containing a clock generator · 5 registered pulse train via the D / A converter 12 fed back to the control amplifier 3 and thus the control loop is adjusted. Upon reaching the balance, the pulse train emanating from the sequence control circuit is terminated. The words contained in the aperture value memory 7 and the exposure time memory 8

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Information from ζ. B, k = 5.6 and t = ^1/125 s are visualized by means of the digital display fourteenth

If, after actuation of the memory key 17 present on the camera and "the memory circuit 6 now effective, the light quantity impinging on the photoreceptor increases by, for example, 2 light levels (2 L), the information in the memory 7 and 8 does not increase Such light-current changes are possible, for example, when the final shooting position is taken in backlight shots after a subject measurement and a second measurement is performed therefrom. When the camera shutter is pressed further, the lens shutter 11 begins to close under spring force. At the same time, the working register 5 is detuned in accordance with the value written in the aperture value memory 7 as soon as the associated control loop detuning results from the reduction of the illuminance f the photoreceptor 2 is balanced again, the electromagnet 10 is de-energized and the shutter closing process stopped. Thus, the aperture with a setting error of z. B *. "- ^1/4 Stage set at the above shown value. In the subsequent work. pulses are fed into the working register 5 and here an exposure time is determined, which corresponds to the changed lighting conditions and takes into account the aperture setting error:

V125 s - L 2 + ¹ / 4L

With retrieval of the information stored in the memory circuit 6 information written in the working register 5 exposure time is restored to the value

V125 s - L 2 + ¹ / 4I + 2 L = ^1/125 s + ¹ / 4L

corrected. The final exposure time thus corresponds to that determined at the time of storage and is corrected by the aperture setting error. After this time, the shutter control solenoid 16 blocking the passage of the trailing closure member up to this point is de-energized via the driver stage 15 and the exposure is terminated. When exposure is completed, the memory circuit 6 is reset to its original position.

The invention has been described above with reference to a camera with automatic iris adjustment. Of course, it is not limited to such cameras, but is also applicable to cameras with manual aperture and light-dependent exposure time education, as well as cameras with automatic program for aperture and shutter speed.

Occasionally recordings with intentional under or overexposure are desired. Also for the circuit according to the invention is suitable. In this case, the camera with the photoreceptor 2 after measuring the shooting scene with open aperture and subsequent closing of the switch 17 by means of the memory button of the camera on an object with respect to the recording scene greater or lesser luminance can be addressed. The thus stored via the flow control 4 in the memory circuit 6 information content up to + _ 2 L is retrieved after the camera trigger and is used for the • desired change resulting from the Arbeitsblendeessung correct exposure time. The in the

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Memory circuit β stored misalignment information is made visible in the digital display Ή for control. The memory contents of the memory circuit 6 is automatically deleted at exposure termination.

Instead of this opto-electrical override input can be done via the switch 18 and a manual incorrect exposure setting. For this purpose, the switch 18 is closed one or more times by means of a further button located on the camera and a signed override signal is written into the memory circuit 6 step by step with each closing. When the camera is triggered, the memory content is superimposed on that of the working register 5, so that in turn results in a corrected exposure time.

Claims (1)

invention claim 1, circuit arrangement for exposure control of photographic cameras with automatic exposure adjustment according to the exposure values determined by an arithmetic circuit during a measurement phase, characterized in that an optionally switchable electronic memory circuit (6) application whose signed information content at camera triggering with the count of an exposure control circuit (5 ) is superimposable, 2, circuit arrangement according to item 1, characterized in that the memory circuit is designed as a circuit which stores the object luminance which rests on specific recording text points. 3, circuit arrangement according to item 1, characterized in that one of a clock generator of a sequence control circuit (4) controlled working register (5) is designed as an actuator for an automatic aperture setting according to a calculated during the measurement phase aperture value and as a counting circuit for exposure time education, based on the Basis of a light measurement with working aperture resulting, a current exposure time corresponding counter reading additionally the information content of the memory circuit is supplied 4 »circuit arrangement according to item 1, characterized in that the memory circuit is designed as an override input circuit, the memory content is automatically deleted at exposure termination, 5ο circuit arrangement according to item 4, characterized in that the memory circuit as opto-electrically 8 212549 controllable override input circuit is formed. 6. Circuit arrangement according to item 4, characterized in that the beidimmende the respective override input signal value by means of a push-button switch (18) is controllable. 7 · Circuit arrangement according to items 1-6 ,. characterized in that the information content of the memory circuit is recognizable by means of a visible in the camera view digital display (14) · Circuit arrangement according to point 1, characterized in that the memory circuit has a resolution of ¹ / 8th exposure levels. For this, · / page drawing