JPS59165035A - Photometric device of camera - Google Patents

Abstract

PURPOSE:To omit a manually operated AE lock by selecting, storing and fixing a partial photometric value when the difference between average and partial photometric values exceeds a prescribed value. CONSTITUTION:When the output difference VM of average and partial photometric circuits 1, 2 is discriminated by a comparator 5, and when the difference VM is less than the prescribed value, an output S1 is turned to H and an average photometric output is selected from a switching circuit 6 and calculated by an arithmetic circuit 9. When the difference VM exceeds the prescribed value, an output S2 is turned to H, a partial photometric output is selected and data DS after operation 9 and A/D conversion 10 are latched. If a main subject is once catched on the center part of a finder visual field and a shutter button is half pressed, the AE lock is performed automatically by selecting a partial photometric value.

Description

DETAILED DESCRIPTION OF THE INVENTION "Unplugging Light" This invention relates to a photometric device for an AE camera.

Follow] q1 bill Interchangeable lens - Eyes Flex AE camera.

The TTL photometry method that takes advantage of this performance is the mainstream, and is divided into average photometry and partial photometry depending on the photometry sensitivity distribution of the screen.

Average metering and partial metering have advantages and disadvantages, and unless an appropriate metering method is selected according to the intention of drawing or the shooting conditions, it is often impossible to obtain accurate metering values or appropriate exposure values.

For example, if the brightness range of the subject is evenly distributed, such as when shooting landscapes in front light conditions, average metering is ideal, but average metering is ideal for shooting people in backlight conditions or stage shots under spotlight lighting. Even if there is a significant brightness difference between the main subject and its surroundings, the brightness of the entire screen is measured as an average, so the metering value may be extremely under or over for the main subject. There are many.

In order to reduce these drawbacks, center-weighted average metering, in which the metering sensitivity gradually increases toward the center of the screen, is often used in current auto-exposure eye reflex cameras. In many cases, the degree of concentration is insufficient, and in order to obtain the appropriate sushi serving value intended by the photographer, it is necessary to correct the exposure by adding an exposure multiple using an exposure correction device or the like.

On the other hand, with partial metering, which measures a limited portion of the screen, it is possible to perform accurate metering for the main subject even under special shooting conditions as described above, but because the metering range is narrow, the screen Determining an exposure value that takes into account the overall balance is difficult and requires a high degree of skill from the photographer.

In order to solve these problems, we have both an average photometry circuit and a partial photometry circuit. An automatic switching photometer has been proposed in which when a predetermined value is exceeded, a partial photometry circuit automatically switches the luminance output to a photometry output.

To explain this using Figure 1, the brightness output by average photometry is B V A + the brightness output by partial photometry is BV
The relationship between the brightness output difference ΔBV=BVA-BVS and the corrected brightness output BVC when the photometric output BVO is BVO=B, VA-BVC is shown in FIG. 1, for example.

That is, when the brightness difference output ΔBV is 121EV or less (
Since the range shown by the arrow AV in the figure) is BVC=0,
BVO=BVA, and the luminance output by average photometry becomes the photometry output. On the other hand, the brightness difference output ΔBV is 121EV
(range indicated by arrow SP and SL:32 in the figure), BVC=ΔBV, so BVO=BVS
Therefore, the luminance output due to partial photometry becomes the photometry output.

In this way, in the case of normal framing where the main subject is captured almost in the center of the frame, accurate metering for the main subject will always be performed even under various shooting conditions, and this will allow for proper fogging during AE shooting. You can get a lot of money.

However, depending on the intention of the image, there may be cases where you want to frame the main subject outside the partial metering area, away from the center of the screen (finder field of view). After capturing the subject and metering it, using a switch or the like to fix the metered value or calculated value according to the photographer's will, a so-called AE lock operation, the desired framing had to be done and the shutter had to be released.

Therefore, it is necessary for the photographer to have knowledge about the shooting conditions under which to perform the AE lock operation, and there is also the risk of erroneous operation of performing normal AE shooting while the AE lock mode is set using a switch, etc. In addition, continuous AE locks that keep the circuit power on can also cause the battery to drain faster.

1 - This invention was made in order to eliminate the drawbacks of the conventional automatic switching photometry device as described above. AE lock is automatically activated under shooting conditions that require AE lock, and AE lock is not activated in other cases, allowing the photographer to focus on drawing, and eliminating the risk of erroneous operation or premature battery consumption. The purpose is to provide equipment.

Therefore, the present invention provides an average photometry circuit, a partial photometry circuit, a brightness difference detection circuit that detects the difference in brightness output from both photometry circuits, and a brightness difference output detected by the brightness difference detection circuit that is set to a predetermined value. In a camera photometry device equipped with a photometry output automatic switching circuit that uses the luminance output from the average photometry circuit as the photometry output in the following cases, and uses the luminance output from the partial photometry circuit as the photometry output when the brightness difference output exceeds a predetermined value, It is equipped with an automatic data fixing circuit that fixes the photometric value or the exposure calculation value based on the photometric value only when the luminance difference output exceeds a predetermined value, that is, when the luminance output by the partial photometric circuit becomes the photometric output. be.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 2 and 3.

FIG. 2 is a block diagram of an exposure control device for a camera to which a photometry device according to the present invention is applied, and shows an average photometry circuit 1.
2-part photometry circuit 29 Luminance output VA, V by both photometry circuits
Differential amplifier 6 as a luminance difference detection circuit that detects the difference in S
．． A switching level setting circuit 4, a comparison circuit 5, and a switching circuit 6, which constitute a photometric output automatic switching circuit. Furthermore, the aperture setting circuit 7.
Film sensitivity setting circuit 8. Arithmetic circuit 9. AD conversion circuit 1
0. Data latch circuit 1 constituting the data automatic fixing circuit
1. and a shutter control circuit 12.

The average photometry circuit 1 detects the average brightness of the entire field of view of the finder and generates a brightness output VΔ. On the other hand, the partial photometry circuit 2 detects the brightness at the center of the viewfinder field of view and generates a brightness output VS.
Then, the differential amplifier 3 inputs the luminance outputs VA and VS from the double-sided optical circuit 19.2, and outputs a luminance difference signal VM corresponding to the difference therebetween.

The switching level setting circuit 4 generates a voltage signal ■T1 that sets the level of the luminance difference signal for switching between average photometry and partial photometry.
．． Output VT2. These voltage signals VT, VT2 are
■When the brightness difference signal when Δ=vs is ■Mo, it is set so that (VT 1 +VT 2 )/2=VMo. For example, VT.

is set to 2 EV, and v'r2 is set to a luminance pressure corresponding to -2EV.

The comparison circuit 5 compares the brightness difference signal VVI from the differential amplifier 3 with the voltage signal VT1°VT2 from the switching level setting circuit, and when ■T1≦VM≦VT2 (for example, the brightness output ■Δ and VS When the difference is 2EV or less), the output signal S is set to a high level "H" and the output signal S2 is set to a low level "L"; otherwise, the output signal S1 is set to a low level "L" and the output signal S2 is set to a low level "L". High level ゛'H
”.

The switching circuit 6 outputs the average photometric luminance output VA when the output signal S1 of the comparator circuit 5 is I('', outputs the partial photometric luminance output VS when the output signal S2 is H'', and outputs the photometric output VO and the output signal VS, respectively. do.

This photometric output {circle over (2)} 0 is input to the arithmetic circuit 9 together with the aperture signal va set by the aperture setting circuit 7 and the film sensitivity signal Vf set by the film sensitivity setting circuit 8 .

Thereby, the calculation circuit 9 calculates the exposure calculation value ES for controlling the shutter speed, converts it into a digital signal I)S by the AD conversion circuit 10, and inputs it to the shutter control circuit 12 through the data latch circuit 11. Control exposure time.

The data latch circuit 11 outputs the input data as is when the signal S2 from the comparator circuit 5 is L'', and latches (fixes) the input data at that time when the signal S2 becomes L''.
Then, the data continues to be output until the shirt release operation is completed.

This data latch circuit 11 also has the function of storing the exposure calculation value necessary when the photometry function is stopped due to the mirror rising in a negative-eye reflex camera.

Note that the photometry operation in this camera is started when the shutter button is pressed halfway, that is, when the shutter button is pressed down in the first stroke.

Therefore, at the first stroke of the shutter button, the output signal S1 of the comparator circuit 5 becomes H'', and when the switching circuit 6 outputs the average photometric luminance output VA, the output signal S2 of the comparator circuit 5 becomes L''. Therefore, the data latch circuit 11 is A
Exposure calculation value data DS from the D conversion circuit 10 is not latched but output as is. Then, in the second stroke, the data DS is latched by the release signal, and the shutter operation begins.

However, when the output signal S1 of the comparison circuit 5 becomes L'' with the first stroke of the shutter button and the switching circuit 6 outputs the partial photometry brightness output VS, the output signal S2 of the comparison circuit 5 becomes H'' at this time. Therefore, the data latch circuit 11 latches the exposure calculation value data DS inputted at that time from the AD conversion circuit 10, and even if the exposure calculation value data changes due to a change in the photometry output ■o, the latched exposure calculation value data continues to be output, and transitions to shutter operation with the second stroke of the shutter button.

For example, when you capture the main subject in the center of the viewfinder's field of view and press the shutter button halfway,
When the photometry output ■o becomes the partial photometry brightness output VS, the exposure calculation value data DS at that time is fixed, so after that, move the main subject to a position away from the center of the viewfinder field, reframe it, and then change the shirt pattern. Even when the camera is released, the exposure calculation value does not change, so proper exposure can be obtained for the main subject.

In this case, the photographer does not need to perform any special operations such as applying E-lock using a switch or the like, so he can concentrate on drawing.

FIG. 3 shows a specific circuit example of this embodiment, and parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

The average photometry circuit 1 uses a photocurrent generated in a photodiode 1'@PD for average photometry provided above the eyepiece of a finder, for example, to an operational amplifier A2 with high input impedance and a log diode 1. It is logarithmically compressed by Dl and converted into a luminance signal voltage.

The partial photometry circuit 2 includes, for example, photodiodes PD for partial all light provided on both the left and right sides of the eyepiece of the finder.
The photocurrent generated at 2 is converted into a luminance signal voltage by an operational amplifier A3 with high input impedance and a log diode LD2.

Then, constant current source I, diode D and operational amplifier A
1, and temperature compensation resistors RT, each having a positive temperature coefficient.

Temperature compensation is performed using RT2, resistors R, R2, and operational amplifier A4 to obtain an average photometric brightness output (voltage) VA and a partial photometric brightness output (voltage) VS.

These brightness outputs VA and VS are 1111
It is output so as to change in the positive direction when one light is detected, and in the negative direction when a bright subject is measured, with respect to the reference voltage VR.

Differential amplifier 3 includes resistors R3 to R6 and operational amplifier A6.
When the difference between the luminance outputs VA and VS is zero, the output VM of the operational amplifier A6 becomes the reference voltage level vT3,
When there is a difference between VA and VS, the output VM of the operational amplifier A6 deviates upward or downward from the reference voltage level according to the magnitude relationship and the magnitude of the difference.

The switching level setting circuit 4 connects the reference voltage ■R to the resistor R7+R.
Divided by a series circuit of Q + R9, three voltage levels V
T1. VT2, VT3 (VTI > VT3 > VT
2) Set. Voltage level ■T3 and VT,,V]'
For example, the difference from 2 is equivalent to 2 EV.

The comparison circuit 5 includes two oven collector output comparators CP1. CP2 and] (consisting of a window comparator circuit consisting of resistor R1o and an inverter G2 that inverts its output signal S1, and when VT2〈vM〈VT1, the output signal S1 is set to high level ゛H'' and the output signal S2
is set to low level "L", and when VM:>V T or VM(V)'2, the output signal S is set to low level "L".
= to make the output signal S2 high level.

An analog switch AS forming the switching circuit 6.

Ag3 each uses the output signal 5lyS2 of the comparator circuit 5 as a control input, and when this control input is 'H', it becomes me and outputs the average photometric luminance output VA or partial photometric luminance output VS as the photometric output V' (1). Output.

The aperture setting circuit 7 includes a variable resistor RΔ that is linked to the aperture ring.
The reference voltage VR is divided according to the aperture setting value to generate an aperture signal Va.

The film sensitivity setting circuit 8 consists of variable resistors R and F linked to the ASA dial, and divides the reference voltage VR according to the film sensitivity setting value to generate a film sensitivity signal Vf.

The arithmetic circuit 9 calculates these photometric outputs o, aperture signals Va,
The film sensitivity signal Vf is input to each input resistor RIs +
Input to the inverting input terminal via R+3 + R14,
It consists of an operational amplifier A7 to which a feedback resistor R16 is connected, and a reference voltage VR is applied to its non-inverting input terminal to form an adder circuit.

The exposure calculation value ES output from this calculation circuit 9 is
The signal is converted into a digital signal DS by the conversion circuit 10, and inputted to the timing circuit 17 of the shutter control circuit 12 through the data latch circuit 11, which determines the time at which the trailing curtain should be locked in the case of a focal plane shutter.

Then, after the leading curtain starts traveling by the shirt tare release, the transistor TR is turned on for the determined time, and the magnet MG is excited to lock the trailing curtain.

The data automatic fixing circuit 16 in this embodiment includes a data latch circuit 11 and a set/reset flip-flop circuit (hereinafter referred to as rFF) for generating the latch signal.
(abbreviated as J) 18, and a resistor R1, which constitutes its initial reset circuit.

It consists of a capacitor C1, an inverter G1, and a resistor R12 and a capacitor C2 that constitute a delay input circuit.

Further, the take-launch circuit 11 also has the function of launching data by inputting the release signal SL at the second stroke of the shirt tab.
・) This data automatic fixing circuit 16 is installed in the A1 ivy 1. When the power supply voltage Vcc is applied with the first stroke of the button, the terminal voltage of the capacitor C1 is initially zero, and the output of the inverter G1 becomes "H" for a certain period of time, resetting the FF18 and outputting its Q output. Set to L''.

When the output signal S2 of the comparator circuit 5 is L'' (during average photometry), this state remains, and the shutter button's first
The data latch circuit 11 does not latch the input data until the release signal SL is input, and outputs the input data as is.

However, when the output signal S2 of the comparator circuit 5 becomes H'' (partial photometry), the terminal voltage of the capacitor C2 becomes H'' with a small delay time determined by the resistor R+2 and the capacitor C2, and the FF18 is set and its Q output to l]″.

Thereby, the data latch circuit 11 launches (fixes) the exposure calculation value data DS at that time, and thereafter continues to output the launched data until the release operation is completed.

This data automatic fixing circuit 16 is provided with a timer circuit 1 day consisting of a resistor R17, a capacitor C3, and an inverter G3, and an AND circuit 20, as shown in FIG.
After c is applied, the output of inverter G3 is made to be lI= for, for example, 100m5, and only when the terminal voltage of capacitor C2 becomes H'' during that time, switch FF18 to cell 1 to make the output H''. , data latch circuit 11
Alternatively, the input data may be latched.

If you do this, the exposure calculation value based on the metering output will be fixed only when partial metering is started from the beginning, such as when you intentionally try to take a backlit photo, and the exposure value calculated by the metering output will be fixed, and if the shooting conditions change during framing. If the average H111 light is automatically switched to partial metering when a composition is not intended by the photographer, an appropriate iE exposure can be obtained without the exposure calculation value being fixed.

Furthermore, this invention can be used as an autofocus A1 core camera.
In particular, when the shutter button is pressed halfway, when the camera is applied to a type of camera that locks the photographing lens once it is in focus, an AND circuit 20 is used to combine the signal S2 and the focus signal, as shown in FIG. Then, only when a focus signal is output in the partial metering state, the FF 18 is set to set its Q output to 1'', and the data latch circuit 11 latches the exposure calculation value data at that time. do it.

That way, when you place the main subject in the center of the viewfinder's field of view and press the shutter halfway, the shooting lens will be locked when the subject is in focus, and if you have switched to partial metering at that time, the exposure will be calculated accordingly. Since the value is fixed, even if the main subject is subsequently moved from the center of the viewfinder field and the shutter is released, the main subject remains in focus and proper exposure can be achieved.

In each of the above embodiments, the exposure calculation value data is fixed when the photometry output VO is the partial photometry brightness output VS, but the photometry output VO is fixed by a hold circuit or the like during partial photometry. The same effect can be obtained.

Effects As explained above, if the photometric device of the present invention is used, the AE lock will be automatically activated under shooting conditions that require the AE lock, without the need to intentionally operate the AE lock using a switch or the like.
Even if the camera is locked and the framing is shifted, the correct exposure for the main subject can be obtained, allowing the photographer to concentrate on creating the image.

There is also no risk of erroneous operation or premature battery consumption.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the operation of a photometer that automatically switches between average photometry and partial photometry, which is the subject of the present invention, Fig. 2 is a block diagram showing an embodiment of the invention, and Fig. 6 is a similar diagram of the same. Circuit diagram showing a specific circuit example, No. 4
5 and 5 are circuit diagrams showing other different examples of the automatic data fixing circuit, respectively. 1... Average photometry circuit 2... Partial photometry circuit 3.
... Differential amplifier (brightness difference detection circuit) 4 ... Switching level setting circuit 5 ... Comparison circuit 6 ... Switching circuit
7...Aperture setting plane path 8...Film sensitivity setting circuit 9...Arithmetic circuit 10...AD conversion circuit 11.
・Data latch circuit 12...Shutter control circuit 13-15...Temperature compensation circuit 16...Data automatic fixing circuit

Claims (1)

[Scope of Claims] 1. An average photometry circuit, a partial photometry circuit, and a brightness difference detection circuit that detects the difference in brightness output by the two-side optical circuit, and a brightness difference output detected by the brightness difference detection circuit that is set to a predetermined value. Photometry of a camera equipped with a photometry output automatic switching circuit that uses the luminance output from the average photometry circuit in the following cases and uses the luminance output from the partial photometry circuit when the brightness difference output exceeds the predetermined value. In the device, when the luminance difference output exceeds the predetermined value, the 81
A photometry device for a camera, characterized in that it is provided with an automatic data fixing circuit for fixing an exposure calculation value based on a first output or its photometric output.