JPH0121487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exposure value display device that can clearly display the relationship between an actual control exposure value and a spot photometric value.

2. Description of the Related Art Exposure meters having both average and spot metering functions have been proposed in the past.

However, such exposure meters only display the metering value corresponding to one of the metering modes selected by the photographer, and do not display the metering value based on either the average metering or spot metering mode. The choice of whether or not to take pictures was based on the photographer's experience and intuition. In addition, when there is a large brightness difference between the main subject and its background, such as when shooting against the light, the metering value may be adjusted to an appropriate value.
The exposure was determined by multiplying by the estimated exposure multiple. The determination of the exposure multiple in this case also relied on empirical intuition and lacked a rational basis. Therefore, for beginners, it is not easy to obtain an appropriate exposure value that matches the intention of drawing using a conventional exposure meter.

Problems to be Solved by the Invention The present invention has been made in view of the above circumstances, and an object of the present invention is to clearly display the relationship between the actual control exposure value and the spot photometry value at the same time. Another object of the present invention is to provide an exposure value display device that can accurately grasp the light distribution state of a subject.

Means for Solving the Problems In order to achieve the above object, the exposure value display device of the present invention receives object light, measures the brightness of a relatively narrow area in the object field, and measures the brightness of a logarithm compression value of the brightness. a control exposure output means for outputting a control exposure value; a difference calculation means for calculating the difference between the output from the spot photometry means and the output from the control exposure output means; and the output of the control exposure output means. a first display means for numerically displaying the control exposure value at a fixed reference position; and a second display means for displaying the amount of difference as a displacement from the fixed reference position based on the difference calculated by the difference calculation means. It is characterized by comprising a display means.

Effects According to the present invention described above, for example, when controlling exposure using an average metering value, the control exposure value is numerically displayed at a fixed reference position, and highlights, etc. in the photographed scene are displayed in a spot. The measured spot photometric value is displayed as a difference from the control exposure value in relation to the displacement from the reference position, so it is possible to predict where the highlighted area will be located on the film's characteristic curve. can.

Embodiments Hereinafter, details of the present invention will be explained based on illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
Cameras to which this circuit is applied are aperture priority TTL
It has a photometric automatic exposure time control function. On the display device, either the average metering value or the manually set exposure value is displayed numerically depending on the mode selected by the photographer, and the exposure value obtained by spot metering is the numerically displayed exposure value. It is displayed as the difference in the number of steps.

In FIG. 1, PD ₁ is a photodetector for average photometry, PD ₂ is a photodetector for spot photometry, and as shown in FIG. 3, photodetector PD ₁ is a pentaprism 22.
The light receiving element PD ₂ is arranged near the eyepiece of the camera body, and the light receiving element PD ₂ is connected to a movable reflector 20 for a single-lens reflex camera, which is positioned as shown in Fig. 3 during image observation. Light from a specific small region of the object field (for example, the region corresponding to the area within the circle 18 in FIG. 2) is taken in through the semi-transparent portion and the mirror 21.
FET ₁ and FET ₂ connected in series with each of the light receiving elements PD ₁ and PD ₂ are field effect transistors used as analog switches that are alternately turned on at a predetermined period. That is, in the circuit shown in FIG. 1, average photometry and spot photometry are performed by time division. Field effect transistor FET ₁ ,
The transistor _Q1 , whose collector is connected to the source of the FET ₂ , is used as a logarithmic compression element that obtains a voltage signal between the base and emitter that corresponds to the logarithm of the photocurrent of the photodetector _PD1 or _PD2 . Potentiometers PM ₁ and connected in parallel with each other
PM ₂ is for introducing information on film sensitivity and preset aperture, respectively. From the sliding terminal W ₂ of the potentiometer PM ₂ , a circuit consisting of the above light receiving element, logarithmic compression element, potentiometer, high input impedance amplifier A ₁ and constant current circuit I ₁ is used. , object brightness,
A signal corresponding to an appropriate exposure time determined according to the film sensitivity and the preset aperture value is output.

However, for subjects with uniform brightness, the light receiving element
It is generally difficult to configure PD ₁ and PD ₂ so that they receive light of the same intensity, so it is usually difficult to configure PD 1 and PD 2 to receive light of the same intensity, so it is usually difficult to configure the slider W for average metering and spot metering for subjects with uniform brightness. The output value at ₁ is different. In order to adjust this difference and correct both signals into equivalent signals, a differential amplifier A ₂ and a potentiometer are used.
PM ₃ and constant current circuit I ₂ are used. Here, in this embodiment, from the slider W ₃ of the potentiometer PM ₃ , the average photometry is calculated, and from the slider W ₄
A signal based on spot photometry is output from. Block 1 is an analog changeover switch that allows the signal from slider W ₃ to pass when the photocurrent of photodetector PD ₁ for average photometry is being sampled, and for passing the signal from photodetector PD ₂ for spot photometry. When the photocurrent is being sampled, the signal from slider _W4 is initially switched to pass. Block 2 is an analog-to-digital converter which converts the average photometry and spot photometry analog signals alternately inputted via analog switch 1 into digital signals. The latch circuits 3 and 4 each latch the A-D converted average photometry value and the spot photometry value each time the A-D conversion operation is completed, and the latch circuit 3 holds the average photometry value. The photometric value of spot photometry is latched in the latch circuit 4 as a digital signal, and the conversion operation of the A-D converter 2 and the latch timing of the latch circuits 3 and 4 are known by the pulses emitted from the control pulse generation circuit 6. It is controlled as follows. Since the configuration of the control pulse generation circuit 6 has no direct relation to the content of the present invention, its details will be omitted.

Change-over switches SW ₂ and SW ₃ are mode change-over switches that can be changed by manual photometry mode selection, and contacts a ₂ and a ₃ correspond to average photometry mode, and contacts b ₂ and b ₃ correspond to spot photometry mode. Block 5 is a speed signal generation circuit that outputs a digital signal corresponding to the manually set shutter speed. switch
SW ₄ and SW ₅ are manual switches that change the exposure time between automatic and manual. The switch SW ₄ , SW ₅
Switching to the _A4 and _A5 side switches to manual mode.
Exposure time is manually set. In this case, the latch circuit 3 selected by switch SW ₂
or 4 is input to the latch circuit 8 via the switch _SW5 . switch
When SW ₄ and SW ₅ are switched to contacts b ₄ and _{b 5} , the latch circuits ₃ and
4 is transmitted to latch circuits 7 and 8. By doing this, the photometry value according to the selected photometry mode is displayed as a step difference with respect to the set shutter speed in a circuit described later.

The latch circuits 7 and 8 are normally switches _SW4 ,
The information input via SW ₅ is refreshed at a relatively slow cycle of, for example, about 0.5 seconds.
This is because the conversion speed in the A-D conversion circuit 2 is on the order of milliseconds (msec), and new conversion outputs are inputted to the latch circuits 3 and 4 every moment, but this information is directly displayed on the display device. This was designed to prevent the display from flickering at a rapid rate when inputting data, making it unsightly.

The latch signal terminal 7a of the latch circuit 7 has
A latch pulse is applied through the AND gate 9, and one of the inputs of the AND gate 9 is normally given a " ₁ " signal through the resistor R1, and the switch _SW6 is closed. “0” when
The signal is applied to close the AND gate 9.

The switch SW ₆ is closed manually by the photographer at any point during photometry. In other words,
When the switch SW ₆ is closed, the "1" pulse generated from the pulse generating circuit 6 cannot pass through the AND gate 9, and the contents of the latch circuit 7 remain latched. The latch circuit 7 etc. is opened when a "1" signal is applied to the latch terminal, takes in input information, and outputs "0".
The information captured by the signal is retained.

Block 10 is a time forming circuit which starts operating in connection with the shutter opening operation and forms a time according to the information held in latch circuit 7. Block 11 is an electromagnet drive circuit that responds to the output of time forming circuit 10 to cut off the excitation of electromagnet Mg for starting shutter closing.

Block 12 is a decoder that converts the exposure time control signal held by latch circuit 7 into a signal suitable for numerical display in seven segment display. The block 13 is a seven-segment display device for displaying the shutter speed, and is arranged, for example, at the center of the right end of the viewfinder field of view, as shown in FIG. A circuit 14 which receives the outputs of both the latch circuits 7 and 8 is a subtraction circuit for calculating the difference in the number of stages between the two outputs. Block 15 is subtraction circuit 1
This decoder converts the output of 4 into a signal suitable for the display format of the display device 16. The display device 16 is constituted by display elements 16a to 16f, 16a' to 16f', which are dots arranged vertically in a vertical line, divided into upper and lower portions of the segment display device 13, as shown in FIG. 2, for example.

In the display device 16, if the exposure information of the latch circuit 8 is overexposure with respect to the exposure information of the latch circuit 7, the upper part of the display device 13 shown in FIG. (are lit), and in the case of underexposure, the light emitting elements in the lower section corresponding to the difference in the number of steps are lit.

Next, the operation of the above configuration will be explained. First, assume that the exposure control mode using average metering is selected. In this case, contacts a ₂ and _{a 3} are connected to switches SW ₂ and SW ₃ , and contacts a 2 and a 3 are connected to switches SW ₄ and SW ₅ .
b ₄ and b ₅ are selected, and the information from latch circuits 3 and 4 is taken into latch circuits 7 and 8, respectively. When a photometry switch (not shown) is turned on (for example, it is turned on in the first step when the shutter button is pressed), power is supplied to each circuit section as is well known, and the latch circuits 3 and 4 receive observation using the finder 17. The average photometric value of the subject image taken and the spot photometric value of the area indicated by the mark 18 in the center of the viewfinder 17 are stored while being updated periodically. The data update cycle at this time depends on the conversion speed of the A/D converter circuit 2, and requires approximately twice the time. Information is taken into the latch circuits 7 and 8 at a speed slower than the data update speed.
Thus, if the average photometric value and the spot photometric value are, for example, 1/500 second and 1/60 second, respectively, in terms of shutter speed, "500" will be displayed on the numerical display 13 as shown in FIG. In the display device 16, a display element 16c' indicating that the amount is under by three steps is lit.
In this way, it can be seen that the 3-level (3Ev) portion where spot photometry is performed is dark compared to the average photometry level of the subject.

Here, when the switch SW ₆ is pressed, the information of the latch circuit 7 that was captured at the time it was pressed is
It will remain as is without being updated. In this way, when the average photometric value is maintained and the camera's optical axis is aligned with any part of the subject and the spot photometric information is captured (in this case, the spot photometric value is periodically updated in the latch circuit 8). The brightness information of any part of the subject can be checked by comparing it with the average photometric value.

Therefore, based on this information, the photographer should control the exposure at the numerically displayed shutter speed based on the shooting intention while taking into account the characteristics of the film such as the film latitude, or It becomes possible to judge whether to add correction or switch to spot photometry control. Now, when the shutter release is performed, the latch circuit 7
An exposure time corresponding to the information is formed in the time forming circuit 10 and exposure is performed.

As a matter of course, the circuit control system is constructed so that the data updating operation in the latch circuit 7 is interrupted during exposure.

Next, in spot metering mode, switch
By switching SW ₂ and SW ₃ , the average photometric value of the latch circuit 3 is loaded into the latch circuit 8, and the spot photometric value of the latch circuit 4 is loaded into the latch circuit 7. In this way, the spot photometric value is displayed numerically on the display device 13, whereas the average photometric value is displayed as a dot indicating the difference in the number of steps. In this case as well, by operating the switch SW ₆ , the spot photometry value can be held in the latch circuit 7 for an arbitrary period of time, and the same information processing operations as in the average photometry mode can be performed.

Furthermore, when switches SW ₄ and SW ₅ are switched to contacts A ₄ and A ₅ , the exposure time is controlled by the manually set shutter speed. , the photometry value of the selected photometry mode is displayed as the step difference with respect to the set shutter speed. This is convenient when giving different exposures to photometric values.

The symbols A, S, and M indicating the shooting modes such as average metering, spot metering, and manual setting may be displayed in the viewfinder in conjunction with the operation of the switch. In the above embodiment, a dot display means is used to display the step difference, but this may be replaced with a numeric display means.

Furthermore, in the above embodiment, the outputs of the two light-receiving elements were sampled alternately in a time-divided manner, and the output terminals of the measurement circuit and the latch circuit were switched in synchronization with the outputs of the two light-receiving elements. Take it out,
It is also possible to perform photographic calculations and A/D converters on each of them, take out the outputs in parallel, and input them to the latch circuits 3 and 4, respectively.

Furthermore, the exposure factor to be displayed and controlled is not limited to the shutter speed as described above, but may also be an aperture value displayed for cameras with shutter speed priority automatic aperture control system, and average and spot metering optics. Needless to say, the system is not limited to the one shown in FIG. 3, and various well-known or well-known systems can be used.

In this case, the number of photoelectric bodies in each light receiving element is not limited to one, and a plurality of photoelectric bodies may be provided in order to obtain a desired average value in average photometry.

According to the present invention as described above, the control exposure value is numerically displayed at a fixed reference position, and the amount of difference between the spot photometry value and this control exposure value is simultaneously displayed as a displacement from the reference position. So,
The photographer can accurately grasp the brightness state of the subject and take pictures under exposure conditions that match the intention of drawing.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing an embodiment of a display device applied to the invention, and Fig. 3 is a light reception for average photometry and spot photometry. FIG. 2 is a schematic diagram showing an example of arrangement of elements. PD ₁ ... Light receiving element for average photometry, PD ₂ ... Light receiving element for spot photometry, 1... Analog changeover switch, 2... A-D conversion circuit, 3, 4, 7, 8...
Latch circuit, 5... Manual setting shutter speed signal generation circuit, 10... Time forming circuit, 11... Electromagnet drive circuit, 12, 15... Decoder, 13, 1
6...Display circuit, SW ₂ , SW ₃ ...Average/spot metering mode selection switch, SW ₄ , SW ₅ ...Manual/
Automatic mode changeover switch, SW ₆ ...Information retention command switch, Mg...Shutter closing control electromagnet.

Claims (1)

[Scope of Claims] 1. Spot photometry means that receives object light, measures the brightness of a relatively narrow area in the field, and outputs a logarithmically compressed value of the brightness, and control exposure output means that outputs a control exposure value. and a difference calculation means for calculating the difference between the output from the spot photometry means and the output from the control exposure output means, and a first display for numerically displaying the output of the control exposure output means as a control exposure value at a fixed reference position. An exposure value display device comprising: means; and second display means for displaying the amount of difference as a displacement from a fixed reference position based on the difference calculated by the difference calculation means. 2. The exposure value display device according to claim 1, wherein the control exposure output means receives the subject light and outputs a logarithmically compressed value of average brightness of a relatively wide area in the subject field. 3. The exposure value display device according to claim 1, wherein the control exposure output means outputs a manually set exposure value.