DE1149983B - Photographic camera with automatic exposure adjustment - Google Patents

Description

GERMAN

PATENT OFFICE

V9718IXa / 57a

REGISTRATION DATE: NOVEMBER 9, 1955

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL: JUNE 6, 1963

The invention relates to photographic cameras with devices for controlling the exposure setting according to the photocurrent of an exposure meter photocell, especially those cameras in which one or more exposure factors, such as Exposure time, lens aperture, film sensitivity, filter factor or the like, can be preset, whereupon a Exposure factor not yet taken into account in the presetting, e.g. B. the time or aperture value, is combined to the exposure value determined by the electric exposure meter.

Such devices of various structural designs are already known. On the technical Defects, e.g. B. when scanning the measuring pointer deflection of a highly sensitive galvanometer and its transfer to the exposure elements to be automatically adjusted, which are likely contribute significantly to the fact that these automatic cameras are not yet on the market have been able to prevail, will not be discussed in more detail at this point. Particularly interested here a disadvantage that is also inherent in all known automatic camera systems, the root of which is in general photographic concerns are to be sought.

The usual method of measuring illumination or light with photographic light meters has the disadvantage that, especially when using interchangeable shooting lenses with a long focal length a much too large cone of light is detected, which too often does not correspond to the integral of the illuminance of the property. The reason for this is the easily understandable demand for to look for the strongest possible adjustment currents for the display instrument. With a larger measuring angle simulated a higher measuring sensitivity. So it happens that with the usual light meters Correction factors determined from empirical values to achieve useful light measurements and by their nature only have the character of probability, must take into account, which should correspond to the respective ratio of object to ambient lighting and an operating experience demand, which cannot be taken for granted with the amateur.

To remedy these disadvantages, it has already been proposed, even for automatic cameras, to work with a small solid angle when measuring light, a solid angle which is only about ¹ Z ₁₀ to V _{15 of} the spatial angle of the taking lens and thus only covers a partial object field that is smaller than a medium photographic object. This proposed device accepts that

Photographic camera with automatic exposure adjustment

Applicant:

Voigtländer Aktiengesellschaft, Braunschweig, Berliner Str. 53

Dr.-Ing. Fritz Faulhaber, Schönaich (Württ.), Has been named as the inventor

the small measuring angle, which can be described as favorable from the photographic point of view, corresponds accordingly weaker photocurrent due and especially with lower illuminance measures for electrical Makes amplification of the measuring current necessary.

The invention has set itself the task of all occurring for photographic recordings Light conditions to carry out the exposure measurement in each case with the optimally most favorable measuring light bundle. You achieve this by the fact that the solid angle of the incident on the photocell and to Light measurement used light beam depending on the illuminance of the light meter detected object is changed automatically. The one according to the invention is particularly expedient Device constructed in such a way that simultaneously with the automatic setting of the last for each correct photographic exposure value necessary exposure factor, i.e. z. B. the exposure time or the lens aperture, also the measuring light angle for the photocell is changed automatically. Through this takes the exposure measurement with bright object lighting with a small one, with low object lighting takes place with a large spatial measuring light angle and is both the respective image motif as well as the prevailing lighting conditions in the recording room. If the lighting density in the object space is high, there are usually also large differences in lighting, z. B. between light and shadow areas. The image content to be photographed is therefore rich in contrast. In these cases, according to the invention, the exposure measurement with a

309 599/164

As far as possible, my light measuring angle is carried out, which is approximately only V _{20 of} the solid angle of the taking lens, whereby of course the most important part of the object is to be measured, which is thus always correctly exposed. If, on the other hand, the illuminance in the recording room is lower, what can be done without hesitation is measured with the device according to the invention with a larger measuring light angle in order to, for. B. to take advantage of a stronger photocurrent during the measurement. The bigger one

Spatial measuring light angle does not do any harm at lower brightness values because the contrasts in the
Recording area are weakened or balanced,
so that in these cases exposure values determined over larger areas of exposure always to 15 exposure meter controlled setting of exposure correct photographic exposure of the negative factor, z. B. the exposure time or the ob-

in no case do the measuring light hit the photocell, which does not come from the subject, and also the light measurement made tends to be even at the largest measuring angle, only after the acquisition, which is important for correct exposure measurement, only important parts of the picture. The change in the limiting angle can be done mechanically, e.g. B. by means of one or more cam disks and tracer pins sliding thereon, or by electrical means, e.g. B. by automatically switching the comparison resistor in a bridge circuit when attaching the lens.

On the basis of a drawn embodiment example for a camera with automatic, from the electric

materials.

If the photographer wants to determine the range of contrast, he only needs to use a small light measuring angle measure one brightest and one darkest image area one after the other and apply both measurement results to compare.

The subject of the invention can be used both with so-called photo elements and with so-called Photocells are realized. It becomes a photoelectric element that emits electricity itself when exposed to light used, an electrical amplifier, e.g. B. a transistor amplifier arrangement may be provided, so that even with very small measuring angles or with lens diaphragms, the invention is still to be described below explained in more detail. Further details of the subject matter of the invention are given. In

1 is a schematic representation of a camera lens with motor-operated adjustment and a focusing device, partly in section;

Fig. 2 shows, also in schematic form, an electrical circuit that can be used for this purpose.

A lens barrel 1 is from a camera shutter 2 with a setting ring 3 for the exposure time and an adjustment ring 4 for the lens diaphragm. The automatic exposure setting, which is determined by a light meter

In particular, low-light illuminations are controlled correctly, a motor 5 causes via an on its own free defined display or automatic adjustment shaft 6 seated differential gear, which in the development can take place. The expense of a special electrical amplifier for the photocurrent

can be saved if according to the invention as

35 teeth of the time setting ring 3 and the aperture setting ring 4 engages. The differential gear consists of the gears 7 and 8, which are loosely rotatably held on the through shaft 6. These two gears 7 and 8 have face gears 9 and 10 on their mutually facing inner sides, which mesh with the two pinions 11 and 12. The pinions 11 and 12 are around a

Highly sensitive organ of the light meter a resistance photocell is used.

The electrical circuit containing a resistive photocell can be carried out by means known per se both temperature-compensated as well as chip-

voltage compensated that the operating voltage 40 common shaft 13 rotatable. The shaft 13 is lower the battery operating the resistance cell in right to shaft 6, with which it is firmly connected. So extraordinary may vary within wide limits, the pinions 11 and 12 can also move around the motor without to influence the measurement result. shaft 6 can be rotated. The gear 7 is with

Experiments have shown that with such a measuring of its face toothing with the timing ring 3 in the arrangement illuminance levels down to about 45 engagement, the gear wheel 8 engages with its face toothing 1 lux can be measured. There are through the voltage in the teeth of the aperture ring 4 a. Invention thus opened up measuring areas in which the
The exposure meter currently available to the photographer has long since ceased to be a display
result. The need for perfect exposure measurement even with low lighting will steadily increase in the future, mainly

The use of the camera can be imagined in such a way that first one of the two exposure factors, namely time or aperture, is manually activated a desired output value is set and locked, whereupon the light value-appropriate allocation the other exposure factor, i.e. aperture or time, is automatically effected by the drive motor 5 will. Depending on whether the time setting ring 3 or the

In cameras with interchangeable lenses, the aperture setting ring 4 is locked in place when dredging For the subject matter of the invention expediently hen the motor shaft 6, the pinion 11 and 12 on the Means are provided which have the effect that when a face gear 9 or on the face gear 10 put a lens in each case the limitation of the roll and drive the respective counter gear 8 or 7 and thus set the appropriate exposure factor, aperture or time.

To the right of the lens mount with the camera shutter is a bundling device for the Measuring light in connection with the photoelectric control part of the automatic and a potentiometer 25 drawn. The light shaft of the bundling device consists of two chambers 14 and 15, which be formed by a tubular housing 16 and a pot-shaped insulating body 17. Front and

because of the increasing sensitivity of the negative material.

Solid angle for the exposure meter changed according to the angle of view of the lens in question will. Preferably only the upper limit is changed, while the lower limit is used for all Lenses remains about the same. The invention suggests that the largest measurement angle should be applied to each Interchangeable lens prefers something (say, to give an approximate figure, lO ^ / o der captured area) is kept smaller than the lens angle of view. Such a measure will

At the rear, the chamber 14 is through a measuring lens 18 and a measuring diaphragm 19, the chamber 15 through this Orifice plate 19 and a circular photocell 20 completed. In a preferred embodiment uses a resistive photocell. The lengths of the chambers 14 and 15 are approximately the same and correspond the focal length of the measuring lens 18. The measuring lens 18 and the photosensitive layer of the resistance photocell 20 have approximately the same diameter. The measuring lens 18 forms in the plane of the measuring diaphragm

19 from. By changing the light passage opening of the measuring diaphragm, you can of the object shown more or less large edge zones are cut away so that only the light from the remaining central zone hits the cell 20 and is measured. But this means that the lighting conditions in the object space with any Spatial angle can be measured, which between the detected by the lens 18 Solid angle and a lower, determined by the orifice plate construction is the smallest value. There too the distance between the measuring orifice 19 and the photocell

20 corresponds to the focal length of the lens, this is determined by the respective aperture for each measurement angle falling light distributed over the entire photocell surface.

The control of the measuring diaphragm 19 is carried out by two mutually movable parts on which the diaphragm blades are attached with one of their ends. According to the illustrated embodiment is one part is designed as a tubular housing 16, while the other as a spur-toothed ring 21 with the insulating body 17 is firmly connected. The toothing of the ring 21 is in engagement with the Toothing of the lens aperture setting ring 4 of the taking lens. The tube 16 carries a wide one Toothed ring 22, which has an intermediate tooth ring 23 and a coupling pin 24 with the timing ring 3 communicates. The intermediate ring 23 is provided to provide a further exposure factor, z. B. the film speed to be able to take into account. To this end he may head towards the Objective axis so far from the time setting ring 3, for example against a spring force, removed until his locking pin 24 emerges from a locking hole 241 of the time setting ring 3 and now the film speed can be adjusted by turning the ring 23 relative to the timing ring 3, after which the Pin 24 engages in another locking hole of the time setting ring 3. For every film speed there is a special one Locking hole 241 is provided. Since the adjusting ring 23 always remains in engagement with the wide toothed ring 22, When setting the film speed, the measuring diaphragm 19 of the bundling device becomes at the same time adjusted and also the position of a potentiometer wiper attached to the housing 16 on a Potentiometer winding 25, which is located on the rotatable insulating body 17, is changed accordingly.

Fig. 2 shows schematically the circuit diagram of the measuring and diaphragm control device according to FIG. 1. It is for the sake of clarity it is assumed that the exposure factor value preselected according to FIG (Time setting ring 3 or aperture setting ring 4) is locked. Therefore, in the scheme of FIG. 2, only the practically the only decisive relative mobility between potentiometer track 25 and potentiometer wiper 26 shown .. The mechanical gear 32 to 37 in Fig. 2 corresponds to the drive path from Motor 5 via the differential gear 6 to 12 either via the ring 4 to the insulating body 17 with the Potentiometer track 25 or via the rings 3 and 23 to the pipe part 16 with the potentiometer wiper 26 in Fig. 1.

The electrical connections α to g provided in FIG. 1 are also identified in the circuit diagram in FIG. 2 at the corresponding points with the letters to g . The measuring bridge contains the

ίο resistor photocell 20, a comparison resistor 27, the potentiometer 25 with the grinder 26, a battery 28 and a switch 29. The two electrical ones Derivatives, namely that of the one between photocell 20 and comparison resistor 27 lying point 30 and that of the grinder 26, lead to an electrical amplifier 31, of which from the amplified differential current of the bridge to the drive motor 5 is conducted. This can be used as a reversing motor be trained. From him is about that

so gear 32 to 37 of the potentiometer wiper 26 emotional.

The potentiometer wiper 26 is moved by a motor until the bridge is adjusted to "zero" is and the motor 5 receives no more power, so it stops. But this means that after the in Fig. 1 drawn embodiment depending on the locked preset value of time or aperture with the Movement for the electrical bridge adjustment to "zero" at the same time the aperture (by means of the ring 4) or the exposure time (by means of the ring 3) is set in accordance with the exposure value.

At this point it should be pointed out that the change in the effective solid angle is a corresponding one Change of the photocell current has the consequence, but that to take this fact into account no additional expenses for compensatory measures are made for the subject matter of the invention will need. According to the invention, the solid angle used for the measurement changes continuously from a very small solid angle at high illuminance levels in the recording room to relative large solid angle with low illuminance levels. The resistance characteristics of the Photo cell compared to, for example, over the entire usable illuminance range with consistently large solid angle recorded course a flattening. But that doesn't mean anything other than that the factor of the change in solid angle acts just as if the cell had one different characteristics. Because now every function potentiometer of an electrical arrangement is known to have to be "adapted" to the other circuit elements, is for the Adjustment of the potentiometer to the newly acquired, flattened cell characteristics no additional compensation measure necessary.

The automatic device according to the invention works according to the illustrated embodiment as follows:

The locking connection 24, 241 between the ring gear 23 and the time setting ring 3 is assumed to be corresponding the sensitivity of the recording material used and thus the influence of this Exposure factor for the position of the measuring diaphragm 19 taken into account. Before the photograph the time or lens aperture ring of the camera shutter is set to a desired value and locked in this position. This pro

choice caused in any case because of the above Gear connections between the lens shutter and the bundling device of the light meter part a corresponding setting of the measuring orifice 19 and the bridge potentiometer 25 or its grinder 26, so that this exposure factor from the photoelectrically controlled automatic is captured. If the camera is now directed at an object to be photographed and the switch 29 is closed, so the final exposure setting takes place automatically according to the measured exposure value. Since the electrical measuring bridge will not be balanced for the time being, a differential current flows from it into the amplifier 31. The amplified differential current rotates the motor 5 in one direction or the other. As a result, in the substitute representation in FIG. 2, the slide 26 is displaced via the gears 32 to 37 as long as until the differential current of the bridge drops to zero and the motor 5 stops. Simultaneously however, the exposure setting has taken place via the motor shaft 6 and its differential gear 9, 10, 11, 12, 13. Is the object space brightly lit, so a great light intensity hits the photocell through the bundling device 20, the bridge equilibrium will only be reached when the measuring orifice 19, and with it also the Receiving aperture, was closed on a relatively small light passage opening. Is on the other hand the object illumination is less bright, so the measuring diaphragm 19 only needs to be reduced in size to establish the bridge equilibrium. It is thus sufficiently clear that the automatic always works with the optimal light measuring angle. With high brightness it is small, with lower brightness is he bigger. With bright lighting and strong contrasts, the strong bundling, so the small spatial angle of the measuring light, only a part of the object space that is important for the image is recorded and thus the photographic recording is correctly exposed. If the lighting is weaker, it will be automatic measured with a larger spatial angle of light, but because of the lower contrasts Misfolding are also avoided. The advantages of the device according to the invention make themselves especially noticeable when taking pictures in poorly lit rooms, because with it, As already mentioned, lighting densities down to a few lux can still be clearly measured can.

Claims (16)

PATENT CLAIMS: 1. Photographic camera with devices for setting the exposure factors according to the Photocurrent of a light meter photocell, characterized in that the solid angle of the on the photocell and used for light measurement depending on the The illuminance of the object detected by the exposure meter changes automatically will. 2. The photographic camera of claim 1, wherein the last to the properly combined exposure value leading exposure factor (exposure time or lens aperture) from one through the photocell current controlled drive is set automatically, characterized in that that the solid angle of the light beam hitting the photocell is simultaneous with the automatic one Setting of the last fogging factor for correct exposure of the recording material is changed. 3. Photographic camera according to claim 1 or 2, characterized in that the light-sensitive Organ (20) of the light meter a resistance photocell 'is used. 4. Photographic camera according to claim 3, characterized in that the electrical, the Circuit containing resistive photocell (20) by using switching means known per se works both temperature-compensating and voltage-independent in such a way that the voltage the battery (28) operating the resistance cell can fluctuate within wide limits without this To influence the measurement result. 5. Photographic camera according to claim 4, characterized in that the electrical circuit a bridge circuit operating according to the zero principle is provided. 6. Photographic camera according to claim 1 to 5, characterized in that means are provided are, through which, when attaching interchangeable taking lenses to the camera, the setting range of the through the Measuring lens on the photocell reaching clearance angle is automatically changed in such a way that the smallest intended clearance angle of this by attaching the various interchangeable lenses controlled arrangement for all interchangeable lenses is about the same, while the largest solid angle depends on the attached taking lens, with the correct one Adaptation of this change in measuring range with regard to the upper spatial angle limit to the electrical Bridge ratios when attaching an interchangeable lens by automatic Switching to a corresponding bridge comparison resistor is effected. 7. The photographic camera of claim 2 and one or more of the foregoing Claims, characterized in that the automatic Behchtungs setting by one Reversing motor (5) is driven. 8. A photographic camera according to claim ?, characterized in that the reversing motor (5) driving the exposure setting also adjusts the focusing diaphragm (19) for the measuring light. 9. Photographic camera according to claim 7 or 8, characterized in that the motor movement is transmitted via a differential gear (7 to 13) to the automatically set exposure factors (3, 4). 10. A photographic camera according to claim 1, characterized in that the bundling device for the measuring light from a lens (18) or a lens system, an iris diaphragm (19) and a resistance photocell (20) and is constructed such that at approximately the same diameter of measuring lens (18), largest measuring aperture (19) and photocell (20) both the distance from the measuring diaphragm to the measuring lens as well as that from the measuring diaphragm to the photocell, for example corresponds to the focal length of the measuring lens. 11. Photographic camera according to one or more of the preceding claims, characterized characterized in that the automatically adjustable setting members (3, 4) of the exposure factors are coupled to the setting device (21, 22) for the measuring diaphragm (19) or bundling device. 12. A photographic camera according to claim 11, characterized in that the setting of the Measuring aperture (19) apart from the automatically adjustable exposure factors of other, additional Exposure factors can be influenced. 13. Photographic camera according to one or more of the preceding claims, characterized characterized in that both the aperture basket and the grooved ring of the orifice plate with tubular extension pieces (16, 17) are provided which together form the housing of the Form bundling device. 14. A photographic camera according to claim 13, characterized in that one of the tubular The extension piece (17) consists wholly or partly of electrically non-conductive material, which carries the potentiometer winding (25) and the resistance cell (20) while from another tubular extension piece of the potentiometer wiper (26) and the measuring lens system (18) are held. 15. Photographic camera according to claim 13 and 14, characterized in that both tubular Extension pieces (16, 17) are provided with teeth, each with a toothed Adjustment member of the taking lens, e.g. B. the time setting ring (3) and the aperture setting ring (4), comb. 16. A photographic camera according to claim 15, characterized in that the toothing (22) of a pipe section (16) is in engagement with an intermediate toothed ring (23), which takes into account further exposure factors (z. B. film sensitivity, filter factor) via detents or couplings (24, 241) is adjustable compared to other exposure factor setting members (e.g. the lens aperture ring or the time setting ring). Considered publications:
German Patent Nos. 637581, 683 925, 871108, 915412, 921371. 1 sheet of drawings © 309 599/164 5.