JPS5928626A - Exposure control system for camera - Google Patents

Abstract

PURPOSE:To enable the detection of the relation between an exposure control value by manual setting and the luminance state of an object in association to the characteristics of a film, by scanning the bright and dark parts on the object with a photometer, obtaining max. and min. values and determining the difference in the number of stages between said values and the signals corresponding to exposing time and an aperture value. CONSTITUTION:A detection switch 32 is closed to scan an object field with a photometer so as to pass the high and low luminance parts on an object. A switch 32 is opened to detect the max. and min. value with a max. value detection circuit 18 and a min. value detection circuit 38, whereafter the slider 58 and slider 72 of a signal generation circuit 54 are set to change adequately the set exposing time or preset aperture value. If said values are so adjusted that the displays of the two signals for the differences between the numbers of stages corresponding to the max. and min. value are symmetrically positioned on both sides with the element 90-13 in the central part of a display part 90 as a center, the level of the exposure is matched with the average value of the max. and min. value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exposure control system for a camera equipped with a photometry device that receives subject light that has passed through a photographic lens and an aperture at a relatively narrow acceptance angle.

Conventional technology Conventionally, luminance information is collected from multiple arbitrary locations on a subject using a spot photometry system with a relatively delicate acceptance angle, and the difference between the multiple luminance information obtained is displayed to display this information. For example, Japanese Patent Laid-Open No. 55-127542 proposes a camera in which an exposure control value is determined based on the photographing intention. In the camera according to this proposal, for example, when measuring two parts of a subject, a high-brightness part and a low-brightness part, first, match the photometry area to one of the parts, press the memorize button, Next, match the photometry area to the other part and press the memorize button/ again. There is no problem if the area of the luminance area to be measured is sufficiently wide compared to the photometric area, but if the area of the luminance area to be measured is in the shape of a point or line, If the area is not very wide, it is not easy to aim at such a brightness area and press the memory button to collect the brightness information, even if it is δ1t.

Summary The present invention makes it possible to collect, for example, the brightness difference between two adjacent parts, or the brightness information of bright or dark areas in the form of points or lines, with a simple operation, and to determine the shooting intention based on the obtained brightness information. The purpose of this system is to propose a camera exposure control system that allows easy setting of exposure control values according to It has circuit means for detecting the value, and a signal generation circuit for generating a signal J corresponding to the manually set exposure time and aperture value. - determining the difference in the number of steps between the maximum value and the minimum value, and simultaneously displaying these differences in the number of steps on a dot display device having a large number of display elements arranged in a row,
If the relationship between the manually set exposure control value and the brightness state of the subject is related to the characteristics of the film, press the push button switch to set the maximum value and minimum value detection circuit to the detection state, and then, for example, determine the maximum and minimum brightness of the subject. Continuously change the direction of the photometer so that it scans the field through the luminance area, and then release the push button. Maximum brightness and minimum brightness information is then captured and displayed in relation to the manual exposure control values.

Embodiment FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a single-lens reflex camera. In Fig. 1, a photographic lens (2), an aperture (4), a half mirror +61,
A pentaprism (B) and the like constitute the main optical element of a single-lens reflex camera. A total reflection mirror (1o) is provided behind the half mirror (6), and guides the subject light to the photometric element (12). A lens barrel (3) containing a photographic lens (2)
) is provided with a known aperture presetting means, and when the aperture value is set by this presetting means, the camera adjusts the amount of mechanical displacement corresponding to the difference in the number of steps between the open aperture value and the set aperture value. Known means of communicating to the body are provided. When the shutter release is performed, the aperture is stopped down to a preset aperture value by a known mechanism. The photometric element (12) receives subject light incident on a relatively narrow area at the center of the photographic screen on the film surface.

This light-receiving area is located within the viewfinder field of view, for example in Figure 3:
It is indicated by the sea urchin mark (M). For example, a photodiode is used as the photometric element (12). A photometric circuit (14) including a photometric element (12) obtains a voltage signal proportional to the logarithm of the intensity of C1 incident on the photometric element (12), and applies this voltage signal from a film sensitivity setting means (16). A signal corresponding to the film sensitivity is calculated, and the aperture (
4) is in the open state, it outputs a voltage signal indicating the N appropriate exposure time determined according to the subject brightness, the maximum aperture value, and the film sensitivity. In other words, if the aperture is left open and exposure is performed with an exposure time corresponding to this output signal, the film will be exposed to an intermediate density.

The maximum value detection circuit (18) detects the maximum value of the output voltage from the photometry circuit (14) during a specified period, that is, while the switch element (2o) is in a conductive state.

The detection circuit (1g) itself has a known configuration and includes operational amplifiers (24>, (26), switch elements (20),
(22), rectifier diode (28), capacitor (
3o) etc.

The switch element (20L (22) is the control electrode (21)
For example, in (23), when a high voltage is applied, the circuit becomes cut off, and when a low voltage is applied, the circuit becomes conductive. When the switch element (22) becomes conductive, the capacitor (3o
) is discharged to place the detection circuit (18) in a reset state. Each of the control electrodes (2]) and (23) of the switch elements (20) and (22) is a detection switch (
32) and a reset switch (34), and is further connected to a system control circuit (36) K, which normally receives a high voltage.

The minimum value detection circuit (38) detects the minimum value of the output of the photometry circuit (4) while the switch element (4o) is in the conductive state. The minimum value detection circuit (38) has a similar configuration to the maximum value detection circuit (18). However, this differs from the maximum value detection circuit in that the connection direction of the rectifier diode (48) is reversed, and that the capacitor (50) is charged to the power supply voltage when reset is completed.

The signal generation circuit (54) is connected to the manually set exposure time.
:Generates a signal according to the aperture value. This signal generating circuit (54) moves the slider (58) at a position corresponding to the set exposure time.
) is set, a constant voltage circuit (60) that provides a constant voltage to the potentiometer (56), and a non-inverting input terminal (64) to the slider (58).
an operational amplifier (62) connected to the operational amplifier (62);
2), one end is connected to the output terminal (68) of the slider (72).
) is connected to the inverting input terminal (66), and the potentiometer (70)
and a constant current circuit (78) that supplies a constant current to.

The slider (72) of the Hoarn 4 meter (70) is
It is interlocked with the aperture limiter throat means, and the amount corresponding to the number of steps between the open aperture value and the aperture value is adjusted from the aperture end -r- (74) toward the terminal (76). It is set in the slid position. The slider (58) outputs a voltage signal indicating the set exposure time, and the terminal (74) connects the voltage signal from the tFJ slider (58) to the terminal (74) of the potentiometer (70). ) and the slider (72), and a voltage signal corresponding to the number of stages described above is added thereto, and a voltage signal is output. This voltage signal vO is transmitted to the photometric circuit '(14), the maximum value and minimum value detection circuit (14), and the maximum value and minimum value detection circuit (14).
8), (38), each output voltage Vl, V2. V5
It is used as a comparison reference signal for voltage signal V,
, V2. As described above, V is a signal indicating the exposure time according to the open aperture value.

Therefore, if these voltage signals are subtracted by the number of aperture steps by the aperture presetting means described above, a voltage signal indicating the "appropriate exposure time" corresponding to the preset aperture value will be obtained. By comparing the "appropriate exposure time" signal and the manual exposure time signal from the slider (58), it is possible to know the relationship between the subject brightness and the set exposure value. On the other hand, in the embodiment, the voltage signal V,
V2. Instead of subtracting the number of aperture steps from V, the number of aperture steps is added to the manual exposure time signal, and the photometry output and the electrical signal corresponding to the manually set exposure value are compared with each other. In this way, three signals V,,v2
．． Instead of reducing the number of narrowing stages from each of V and Noso Jl,
The circuit configuration is simpler if the number of stops is added to one set exposure time signal.

The stage difference detection circuits (80), (82), and (84) are composed of subtraction circuits, and the signals Vl, V, , v3
The signal loss is subtracted from each of them, and the number of steps difference in the positive or negative direction is detected based on the signal Vo. The display device (86) has a number of stages, a difference detection circuit (80), (8
2), output Δv from (84), lΔv2. ΔVs
The K-response exposure deviation value is displayed simultaneously on the display section (90) in the viewfinder in increments of 0.5 steps. Incidentally, a specific example of the configuration of this display device is shown in FIG. Display section (9
0) has a display device in which liquid crystal display elements (90() to (90-25)) are arranged in a row along one side of the viewing field as shown in FIG. 0
They are arranged in five steps of width, and for a difference in the number of steps 0, the central element r-(9(1-13'l) is made to correspond, and for a positive step difference, &'' element r((10-1 ) ~ (Jl O-12),
Also, for negative step number differences, elements (90-14) to (90
-25) is the correspondence. The signal processing circuit (88) sequentially switches and takes in the three analog signals from the step number difference detection circuits (80), (82), and (84) in time series, converts them into digital values, and converts them into codes suitable for the display section. Convert to The exposure time control circuit (92) includes a signal generation circuit (
A signal corresponding to the manual exposure time from the slider (58) in 54) is input, and the exposure time is controlled in relation to the shutter release operation. This circuit (92) is composed of a known time circuit including a logarithmic expansion circuit.

Description of FIG. 2 In FIG. 2, the switching circuit (94) sequentially converts the outputs of the subtraction circuits (60), (62), and (64) of FIG. 1 into switching signals in time series. latch circuit (98),
(100) and (+02) are the subtraction circuits (6
The digital conversion values corresponding to the outputs of 0), (62), and (64) are latched every time AD conversion is performed. Decoder (104), (106), (+
08) are latch circuits (98), (100),
It converts the contents latched in (102) into a code according to the display, and each has a plurality of output terminals, one of which outputs a high voltage depending on the input value. OR gate (106-1,) (t-1~25)
The 3 input terminals are decoder (+04), (1,06
) and (108), which are connected to three signal output terminals having the same level. The display device (+08) has liquid crystal display elements (110-i) arranged in a row in steps of 05, and when the output of the OR gate (+06-i) is a high voltage, the display element (110-i) Driven to display state. The center display element (110(3)) corresponds to the origin, and for example, the difference between the two inputs (V+Vo
) is O, this display element (]1O-13) is driven and displayed. v, -v (1) In the case of 0, the display element (1,
10-]-) to (+1O-12) is also v
When l-Vo<O, the display element (I] 0-,!4
) to (] 10-25) are driven and displayed.

Next, the operation of the circuit with the above configuration will be explained. When the power switch (94) is closed and the circuit is in a power supply state, the system control circuit (36) temporarily disconnects the low voltage from the terminal (39).
- output maximum value and minimum value detection circuit (18),
(38) is reset. Under the reset state, the difference in the number of stages Δ■1.corresponding to the outputs of both detection circuits (82) and (84). The display of Δv2 is prohibited, and only the step number difference Δ■o corresponding to the output of the photometric circuit (14) is displayed. Next, while observing the subject through the finder,
The detection switch (32) is closed and the field is scanned by the photometer through the high and low brightness areas on the subject, after which the detection switch (32) is opened. Furthermore, after the detection switch (32) is closed, the reset switch (3
4) is closed and both detection circuits are reset, the above-mentioned display inhibiting operation is canceled. Now, after detecting the maximum and minimum values, by appropriately changing the set exposure time or preset aperture value, the display of the two step difference signals corresponding to the maximum and minimum values will be displayed on the center element (90- 1 and 3) so that they are located symmetrically on both sides, the exposure amount level is matched to the average value of the maximum value and minimum value. By setting the exposure amount in this way, if the difference between the maximum value and the minimum value is within the latitude range of the film, an exposure is made that captures the most information about the subject brightness. If the difference exceeds the film latitude, for example, you may want to record details in high-brightness areas even at the expense of low-brightness areas.
Change the setting value and reduce the exposure amount so that the maximum value displayed in 6) falls within the latitude. If you change the setting value such as the aperture value to reduce the amount of exposure, the display position of the maximum value and minimum value will be shifted in the negative direction by the number of steps decreased. Therefore, if the ball is shifted until the display position of the maximum value coincides with at least the display element that is separated from the central element (90-1, 3) by the number of steps corresponding to half the latitude +1a in the positive direction, the ball is shifted. ,
In this case, the appropriate exposure amount is set. Note that the latitude of a film varies depending on the type of film, and for black and white film, it can be changed through development processing.

Therefore, it is desirable for the photographer to obtain information in advance about the characteristics of the film to be used. Further, it is not necessary that the element r·(90-13) at the center corresponds to the center of latitude, and the photographer is free to determine a position suitable for him based on his own photographic experiments and photographic experience. After collecting the maximum and minimum values, the relationship between these and any part of the object can be determined by displaying the output ΔV(,) of the step difference detection circuit (80). For example, , it is possible to know which part of the subject has the brightness exceeding the latitude F. In this way, the photographer can predict the photographing result.

Next, after determining the exposure amount as described above, release the shutter.7.The aperture (4) is stopped down to the preset aperture value in a known manner, and then the shutter is opened and the exposure is performed at the set time. Booths are controlled. In addition, the maximum value and minimum value detection circuit (1
8) and (38) may be reset in connection with the shutter release, or may be reset only in response to a manually operated reset switch (34). Also the detection switch (32)
is linked to an operating member such as a push button or a lever, but if the reset switch (34) is linked to the same operating member, seven can be created. For example, when a push button is used, maximum value and minimum value detection operations may be designated in the first stage of pushing, and reset may be performed in the second stage.

In the embodiments described above, analog circuits such as the maximum value and minimum value detection circuits (18) and (38) are used, but these may be replaced with digital circuits. In this case, the output signal of the photometric circuit (14) should first be converted into a digital signal. Further, the present invention is applied to a camera system in which the aperture value is set by an aperture presetting means on the photographing lens side, and the difference in the number of steps between the open aperture value and the preset aperture value is transmitted to the camera body side. Although shown, the present invention can also be applied to a camera system in which the aperture value is set on the camera body side.

According to the present invention, there is provided a detection means configured to detect the maximum value and minimum value of the photometric output during the period in which the detection operation is instructed by the detection designation member.
Therefore, information on the maximum and minimum values during scanning can be obtained by instructing the detection operation using the detection designation member and scanning the bright and dark areas on the subject with appropriate photometry. The detection operation in this case is extremely simple;
Moreover, it is also possible to easily obtain luminance information of any two parts. The obtained information is displayed in relation to the manually set exposure control value, and the state of subject brightness can be understood in relation to the exposure control value and film characteristics.
It is possible to easily find and determine the exposure control value according to the shooting intention.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
A circuit diagram showing a specific example of the configuration of the display device (86) in the circuit diagram of FIG. 1, and FIG. 3 is a diagram showing an example of the configuration of the display section of the display device in the finder. 2. Photographing lens, 4. Aperture, 6. Half mirror 11
4...Photometering circuit, 18...Maximum value detection circuit, 38...
Minimum value detection circuit, 54...Signal generation circuit, 80.82
．． 84 Level difference detection circuit, 86... Display device, 92
・Exposure time control circuit, 90-1...Display element applicant Minolta Camera Co., Ltd.

Claims (1)

[Scope of Claims] Photometry means that receives subject light that has passed through a photographic lens and an aperture at a relatively narrow acceptance angle, and outputs an electrical signal that is in a linear relationship with the logarithm of its intensity, and for a period specified from the outside. a maximum value and minimum value detection circuit for detecting the maximum value and minimum value of the electric signal output from the photometric circuit; a manual operating means for instructing the detection operation of the maximum value and minimum value detection circuit; a signal generation circuit that generates an electric signal according to an exposure time and an aperture value; and, based on the output signal of the signal generation circuit, this output signal and each output signal of the maximum value detection circuit and the minimum value detection circuit. first and second step difference detection circuits for detecting the step difference between the steps; display means for simultaneously displaying values corresponding to the output signals of the first and second step difference detection circuits; and a shutter. An exposure control system for a camera, comprising: an exposure control means for performing exposure with an exposure time and aperture value manually set based on a release.