JPH11153487A - Photometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a convenient photometer in which release time lag will not be prolonged even if the subject of photography is of low brightness. SOLUTION: In this photometer, photocurrents proportional to the amounts of incident light beams are integrated by an integrating capacitor 33, and the voltage of the integrating capacitor 33 is detected by an A/D converting circuit 34 in a CPU 1. Measurement time from the start of integration by the integrating capacitor 33 is measured by a timer in the CPU 1. If the integrated voltage has reached a predetermined voltage value before a predetermined measuring time has elapsed, data about the brightness of the subject of photography are computed in the CPU 1 according to the timer count data. If the predetermined time has elapsed before the integrated voltage has reached the predetermined voltage value, the data about the brightness of the subject of photography are computed from the predetermined voltage value, the predetermined time, and the voltage value detected by the timer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric device,
More specifically, the present invention relates to a photometric device used for an optical device such as a camera.

[0002]

2. Description of the Related Art In recent years, in a photometric circuit of an optical device such as a camera, an incident light beam is converted into a photocurrent using a photodiode, and this is converted into a logarithmic compression voltage, or the photocurrent is stored in a capacitor. A / D conversion is performed. In these cases, a comparator for A / D conversion and a reference voltage generating circuit are required for compression, and a bipolar IC has been used.

In such a photometric circuit, photometry is performed using an IC for photometry and a CPU in a camera. However, the circuit scale becomes large, the development process becomes complicated, and the cost becomes high. Had a problem.

In order to solve this problem, a photodiode and an integrating capacitor are connected to an input / output port of a CPU, and the integrating capacitor is charged (discharged) with a photocurrent, for example, in Japanese Patent Laid-Open No. 4-181128. In such a case, there is disclosed a photometric device technology that obtains the subject brightness from the time until the input gate is inverted, and realizes a simplified and low-cost photometric device without using a bipolar IC.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 4-181 is disclosed.
In the technique disclosed in Japanese Patent No. 128, the open drain transistor is turned on, the charge of the integrating capacitor is discharged, and then the input gate is inverted when the charge reaches a predetermined value. I have. The time required from when the transistor is turned on until the gate is inverted is a release time lag.

[0006] However, Japanese Patent Laid-Open No. Hei 4-18112 discloses
In the technique disclosed in Japanese Patent Application Laid-Open No. 8 (1996) -1996, when the subject has low luminance, the photocurrent becomes small, so that it takes a very long time to integrate until the input gate is inverted. Therefore, in such a case, the release time lag is long, and it is difficult for the user to use.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a photometric device which is easy to use without increasing the release time lag even if the subject has low luminance.

[0008]

That is, the present invention provides an integrating capacitor for integrating a photocurrent according to the amount of incident light, a detecting means for detecting a voltage of the integrating capacitor, and a measuring time from the start of integration of the integrating capacitor. Means for measuring the subject brightness data based on the time measurement data of the time measurement means, when the integrated voltage reaches a predetermined voltage value before the measurement by the time measurement means elapses a predetermined time. And calculating means for calculating the subject luminance data from the predetermined voltage value, the predetermined time, and the voltage value detected by the detecting means when the predetermined time has elapsed before the voltage reaches the predetermined voltage value. It is characterized by the following.

Further, the present invention relates to a photometric device for integrating a photocurrent output from a light receiving element with an integrating capacitor and outputting subject luminance data based on time data until the integrated voltage reaches a predetermined voltage value. If the integrated voltage of the integrating capacitor does not reach the predetermined value even after a predetermined time has elapsed from the start of the integration, the integration voltage is calculated from the predetermined time value and the integrated voltage value at that time until the predetermined voltage is reached. And a brightness calculation means for calculating subject brightness data based on the time calculated by the prediction calculation means.

Further, the present invention relates to a photometric device for integrating a photocurrent output from a light receiving element with an integrating capacitor and outputting subject brightness data based on time data until the integrated voltage reaches a predetermined voltage value. If the integrated voltage of the integrating capacitor does not reach the predetermined voltage value even after a predetermined time has elapsed from the start of the integration, a brightness calculating means for calculating the subject brightness data based on the integrated voltage at that time. It is characterized by having.

In the photometric device according to the present invention, the photocurrent corresponding to the amount of incident light is integrated by the integrating capacitor, and the voltage of the integrating capacitor is detected by the detecting means. The measuring time from the start of the integration of the integrating capacitor is measured by a timer. Then, the arithmetic means calculates the subject luminance data based on the time data of the clock means when the integrated voltage reaches a predetermined voltage value before the measurement by the clock means elapses a predetermined time. On the other hand, if the predetermined time has elapsed before the integrated voltage reaches the predetermined voltage value, the subject brightness data is calculated from the predetermined voltage value, the predetermined time, and the voltage value detected by the detection means. .

Further, according to the present invention, a photometric device for integrating a photocurrent output from a light receiving element with an integrating capacitor and outputting subject brightness data based on time data until the integrated voltage reaches a predetermined voltage value. In the above, when the integrated voltage of the integrating capacitor does not reach the predetermined value even after a predetermined time has elapsed from the start of the integration, the predicting operation means calculates the predetermined time value and the integrated voltage value at that time. And the time until the above-mentioned predetermined voltage is reached is predicted by the prediction calculation means. Then, the subject brightness data is calculated by the brightness calculation means based on the time calculated by the prediction calculation means.

Further, according to the present invention, a photometric device for integrating a photocurrent output from a light receiving element with an integrating capacitor and outputting subject luminance data based on time data until the integrated voltage reaches a predetermined voltage value. In the above, when the integrated voltage of the integrating capacitor does not reach the predetermined voltage value even after a predetermined time has elapsed from the start of the integration, the luminance calculating means uses the integrated voltage at that time as the subject. The luminance data is calculated.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a camera having a photometric device according to a first embodiment of the present invention.

In FIG. 1, a CPU 1 sequentially executes sequential control based on a program stored in a ROM provided therein, thereby controlling operations of peripheral ICs and the like. The CPU 1 includes an AF (autofocus) IC 2, an EEPROM 6, an interface 7, encoders 13, 14, 16, and a DX circuit 1.
7, a strobe unit 18, a liquid crystal display panel 19, a date imprint circuit 20, a reset IC 21, and the like are connected.

The AF IC 2 measures the distance to the subject by an infrared active method, and transfers the obtained subject distance information to the CPU 1 by 8-bit serial communication. The AF IC 2 is connected to a light emitter / receiver 5 composed of three IREDs 3 for light emission and one PSD 4 for light reception, thereby measuring the distances of three points on the shooting screen. You can do it.

In these projectors 5, if there is a variation in the base line length between the constituent elements IRED 3 and PSD 4, the subject distance information obtained as a distance measurement indicates that the base line length does not vary. If it does not exist, it deviates from the distance measurement data obtained. Therefore, the following EEP
Correction calculation is performed based on the data stored in the ROM 6, and the correction is appropriately made.

The EEPROM 6 is constituted by a nonvolatile storage element, and the error caused by the dispersion of the shorthand data and the mechanical fluctuation of the lens when converting the distance measurement data into the data of the lens. Is stored in the memory for adjusting the data during production.

The interface 7 is an IRED3
Then, the power supply stabilizing circuit 8 of the CPU power supply _VDD and the pre-drivers of the motor driver 9 and the plunger driver 10 are driven. The motor driver 9 drives the film feeding motor 11 and the taking lens driving motor 12, respectively. The film feeding state is detected by the encoder 13, and the driving position of the photographing lens is detected by the encoder 14. These detection results are supplied to the CPU 1.

The shutter of a camera (not shown)
Driven by the plunger 15, the start of the shutter opening is detected by the encoder 16 and supplied to the CPU 1.

The DX circuit 17 is for detecting the ISO sensitivity of the film.
It is supplied to U1. The strobe unit 18, the liquid crystal display panel 19 and the date imprinting circuit 20
Based on the signal of No. 1, flash light emission, display of a mode, the number of film frames, and the like, and date imprinting are performed.

The reset IC 21 is a power-on reset IC for the CPU 1. This reset IC 21
This is for keeping the CPU 1 in a reset state until the power supply V _DD of the CPU 1 reaches the operable voltage of the CPU 1 when the power supply battery is turned on. Even if the power supply V _DD is temporarily interrupted, the CPU 1 does not run away. It is designed to prevent it.

Further, the CPU 1 includes various switches 2
2-28 and light emitting diodes 29-30, photodiode 32 and capacitor 33 which are light receiving elements for photometry
Is connected.

That is, the first release switch (R1SW) 22 is a switch that operates when the release button is half-pressed. When the first release switch 21 is turned on, the distance measurement is performed, and the measured distance value at this time is stored in the CPU 1.

Second release switch (R2SW) 2
Reference numeral 3 denotes a switch that operates when the release button is fully pressed. When the second release switch 23 is turned on, the taking lens is extended based on the distance measurement value, and the exposure is controlled based on the photometry value.

A flash mode switch (FLSS)
W) 24 is a switch for switching between a red-eye emission mode, a strobe off mode, and a strobe forced emission mode. Here, the red-eye emission mode is a mode having a flash photography function that can prevent a red-eye phenomenon described later.

A self-timer switch (SLSW)
Reference numeral 25 denotes a switch used for photographing in the self-timer mode, and a forced rewind switch (RWMSW) 26
A switch is operated to rewind the film when the film loaded in the camera is rewound halfway. Furthermore,
A barrier switch (BRSW) 27 is a switch that is operated when opening and closing a barrier provided on the front surface of the photographing lens, and a back cover switch (BKSW) is a switch that is operated when opening and closing the back cover on the back of the camera. It is.

Further, the light emitting diodes 29 and 30 are indicator lights in the viewfinder, and perform an AF ranging end and a short distance warning, a strobe light emission warning, a red-eye occurrence warning, and the like. The light emitting diode 31 is a light emitting diode for self-mode display.

The above-mentioned red-eye is a so-called red-eye phenomenon in which the subject's eyes appear red when the subject is flashed by the flash unit 18 and photographed. Therefore, the above-mentioned red-eye occurrence warning means that when the occurrence of the above-mentioned red-eye phenomenon is detected in advance, the flash mode changeover switch 2
4 is a warning urging the user to switch the mode to the red-eye mode.

The photodiode 32 is for measuring the luminance of a subject. The anode terminal of the photodiode 32 is connected to an integration capacitor 33 and to an A / D conversion circuit 34 and an N-channel (hereinafter abbreviated as Nch) open drain transistor 35 in the CPU 1. On the other hand, the cathode terminal of the photodiode 32 is connected to the reference voltage Vcc.

In this photometric device, the photodiode 32
The voltage generated by charging the integration capacitor 33 with the photocurrent generated according to the amount of incident light at A / D
It is detected by the conversion circuit 34. The time until the integrated voltage reaches a predetermined voltage is measured, and the measured data is converted into subject brightness data.

Next, with reference to the timing chart of FIG. 2, the operation of the photometric device when the subject brightness is not low and when the subject brightness is low will be described. FIG. 2A is a timing chart for explaining the operation when the subject brightness is not low and the brightness is normal.

When the reset signal changes from low level (L) 1 to high level (H), the integration transistor 35 is turned on. As a result, the electric charge stored in the integrating capacitor 33 is discharged. Thereafter, when the reset signal returns to the low level after a predetermined time has elapsed, the integrating transistor 35 is turned off again.

At this point, the integration capacitor 33 starts to be charged by the photocurrent of the photodiode 32. That is, integration starts. A change in the charging voltage of the integration capacitor 33 (hereinafter, referred to as integration voltage) is monitored by an A / D conversion circuit 34. Since the rate of change of the integrated voltage changes according to the photocurrent from the photodiode 32, that is, the subject brightness, the subject brightness can be obtained by measuring the time t until the integrated voltage reaches a predetermined threshold voltage _VTH. Can be

Next, the case where the subject brightness is low will be described with reference to the timing chart of FIG. When the subject is very dark, that is, when the photocurrent is small, the integrated voltage rises slowly as shown in FIG. Therefore, this integrated voltage is equal to the threshold voltage V _TH
The time to reach is very long. However, since this time is related to the time lag in the photographing sequence, it is not preferable to increase the time.

Therefore, in this photometric device, if the integrated voltage does not reach V _TH even after a lapse of a predetermined time (limit time t _lim ) from the start of integration, the integrated voltage at that time (FIG. In the case of), the time (t _cal ) from V _lim ) to V _TH is calculated by the following equation (1). t _cal = (t _lim / V _lim ) · V _TH (1) Here, V _lim is an integrated voltage at the time limit time t _lim .

Thus, the time spent for photometry is t
Since it does not exceed _lim , the time lag can be reduced. The above-mentioned time limit t _lim is, for example, 7 msec. And the setting can be changed without being limited to this value.

Here, the photometric operation in the first embodiment will be described with reference to the flowchart of FIG. First, in step S1, a timer (not shown) in the CPU 1 is reset. Then, step S
At 2, the reset signal changes from a low level to a high level and is output for a predetermined time. At the same time, the integration transistor 35 is turned on for a predetermined time. As a result, the integration capacitor 33 is reset, that is, the electric charge is discharged.

Thereafter, when the timer is started in step S3, the process proceeds to step S4, where the value of the integration capacitor 33 is A / D converted, and the integration voltage is read. Here, in step S5, it is determined whether or not the above-described time limit t _lim has elapsed since the start of the timer. If the time limit t _lim has not elapsed, the process proceeds to step S6, and it is determined whether or not the integrated voltage has reached a predetermined threshold voltage V _TH . If it does not reach the threshold voltage V _TH is returned to step S4, steps are repeated S4~S6 described above.

On the other hand, if it is determined in step S6 that the threshold voltage _VTH has been reached, the process proceeds to step S7,
The timer value t at that time is read. On the other hand, when the integration voltage reaches the time limit t _lim before the integration voltage reaches the threshold voltage V _TH during charging of the integration capacitor 33,
The process moves from step S5 to step S8.

In step S8, the charging completion time of the integrating capacitor 33 is calculated as a predicted calculation time.
It is obtained by the above equation (1). Next, step S9
, The predicted operation time t _cal is read in place of the timer value t.

When the timer value t is read in this way,
Proceeding to step S10, the timer value t becomes the subject brightness value BV
Is converted to That is, after the timer value t is logarithmically compressed, it is converted into the subject brightness value BV.

As described above, when the charging time of the integrating capacitor 33 exceeds the predetermined time limit, the charging time is obtained by the calculation, so that the photometry can be performed without increasing the time lag even at a low luminance.

In the above-described embodiment, the integration capacitor is once discharged and then charged with the photocurrent. However, the present invention is not limited to this. For example, the battery may be charged once at Vcc, then discharged (inversely integrated) with a photocurrent, and the time required to decrease to a predetermined voltage may be measured.

In the first embodiment, the predetermined threshold voltage V _TH and the limit time t _lim are stored as fixed values in a ROM (not shown) inside the CPU. Considering this, the setting may be made for each device.

For example, an integral characteristic of a subject having a predetermined luminance is measured, and an optimum threshold voltage V _TH and a limit time t _lim are set in accordance with the measured characteristics. May be read.

Also, depending on the shooting conditions and the exposure mode,
In some cases, it may be desirable to give more importance to photometric accuracy than to time lag. In this case, if the values of the threshold voltage V _TH and the time limit t _lim are set according to the shooting mode, it becomes easier for the photographer to use.

The second embodiment is an example of the setting of the time limit t _lim in consideration of such a photographing mode and the like. FIG. 4 is a flowchart illustrating an example of the operation of setting the time limit t _lim of the photometric device according to the second embodiment of the present invention.

In steps S11 to S13, it is determined whether the setting mode of the camera is the night scene mode (step S1).
1) Whether the flash mode is off (step S1)
2) Whether the mode is the self-remote control mode (step S1)
3) is determined. If any of the modes in steps S11 to S13 is applicable, the process proceeds to step S18, and the time limit t _lim is set to a predetermined time “C”.

If it is determined in each of the steps S11 to S13 that the mode is not any of the modes, the process proceeds to the step S14.
It is determined whether is in the continuous shooting mode. Here, if the mode is not the continuous shooting mode, it is determined in a succeeding step S15 whether or not the mode is the time lag reduction mode.

In steps S14 and S15,
If it corresponds to any of the modes, the process proceeds to step S16, and the time limit t _lim is set to a predetermined time “A”. On the other hand, if it is determined in steps S14 and S15 that none of the modes is applicable, step S1
Proceeding to 7, the time limit t _lim is set to a predetermined time “B”.

As described above, in the routine for setting the time limit t _lim , three types of set times can be changed in steps S16 to S18 according to various modes. In this case, the normal integration limit time is set to B [msec. ]
The relationship is set as A <B <C.

Thereafter, a photometry routine is started.
Since the flowchart of FIG. 3 may be executed, the description thereof will be omitted. The various modes in which the setting of the time limit t _lim can be changed are not limited to the above examples.

Next, referring to the flowchart of FIG.
A third embodiment of the present invention will be described. In the above-described second embodiment, photometry is performed after switching the limiting time t _lim of the integration capacitor according to the camera mode. However, in the third embodiment, photometry is performed again according to the subject brightness. Is performed.

First, in step S21, B, which is a normal integration limit time, is set to t _lim . Next, photometry is started in step S22. In this case, the photometry routine of FIG. 3 described above may be executed, and a description thereof will be omitted.

Then, in step S23, it is determined whether or not the integration limit time t _lim has elapsed. here,
If it is determined that the integration limit time t _lim has not yet elapsed, the photometry is completed assuming that the photometric value has been determined. If the integration limit time t _lim has elapsed, step S
Proceeding to 24, it is determined whether re-photometry has been performed.

If it is determined in step S24 that the photometry has been completed, the photometry is completed. On the other hand, if the photometry has not been performed again, the process proceeds to step S25, and the value “D” at the time of low luminance is set to the integration limit time t _lim . Thereafter, step S22
And the photometry is started again.

As described above, once the photometry is performed, the integration limit time can be reset according to the luminance of the subject. According to the above embodiment of the present invention, the following configuration can be obtained.

That is, (1) a light receiving element for outputting a photocurrent corresponding to the amount of incident light, an integrating capacitor for integrating the photocurrent output from the light receiving element, and a detecting means for detecting an integrated voltage of the integrating capacitor. A timer for measuring the time from the start of integration of the integrating capacitor; and, when the integrated voltage reaches a predetermined voltage value before a predetermined time elapses during the measurement by the timer, the timer of the timer is used. Subject brightness data is calculated based on the data, and if the measurement by the timing means has passed the predetermined time before the integrated voltage reaches the predetermined voltage value, the predetermined voltage value, the predetermined time, and the detection Calculating means for calculating the subject luminance data from the voltage detected by the means.

(2) The photometric device according to (1), wherein the predetermined time can be changed according to a photometric mode. (3) In a photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined value, from the start of the integration. When the integral voltage of the integrating capacitor does not reach the predetermined value even after the lapse of the predetermined time, a time until the predetermined voltage is reached is calculated from the predetermined time value and the integrated voltage value at that time. A photometric device comprising a predictive calculation means.

(4) The photometric device according to (3), wherein the predetermined time can be changed according to the photometric mode. (5) In a photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined value, from the start of the integration. If the integrated voltage of the integrating capacitor does not reach the predetermined value even after a predetermined time has elapsed, the image processing apparatus further includes a luminance calculating unit that calculates the subject luminance data based on the integrated voltage at that time. Photometric device.

(6) The photometric device according to (5), wherein the predetermined time can be changed according to the photometric mode. (7) In a photometry method in which a photocurrent output from a light receiving element is integrated by an integration capacitor and subject brightness data is output based on time data until the integrated voltage reaches a predetermined voltage value, the integrated voltage is If a predetermined time has elapsed from the start of the integration by the integrating capacitor before reaching the predetermined voltage value, the time required to reach the predetermined voltage value from the predetermined time value and the integrated voltage value at that time is determined. A photometric method characterized by performing a prediction operation.

(8) The photometric method according to (7), wherein the setting of the predetermined time can be changed according to a photometric mode. (9) The photometric method according to (8), wherein the predetermined time can be reset according to the subject brightness.

(10) In the photometry method, a photocurrent output from a light receiving element is integrated by an integration capacitor, and subject brightness data is obtained based on time data until the integrated voltage reaches a predetermined voltage value. A first step of resetting an integrated voltage of a capacitor and starting a predetermined measuring time; and determining whether a predetermined time has elapsed from the start of integration by the integrating capacitor before the integrated voltage reaches the predetermined voltage value. A second step of judging whether the predetermined time has elapsed in the second step and a time until the integrated voltage reaches the predetermined voltage value based on the integrated voltage value at that time. A third step of performing a prediction operation.

(11) The predetermined time can be changed according to the photometry mode.
The photometric method according to 0). (12) The photometric method according to (10), wherein the predetermined time can be reset according to the brightness of the subject.

(13) In a camera having a photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined value. If the integrated voltage of the integrating capacitor does not reach the predetermined value even after a predetermined time has elapsed from the start of the integration, the integration voltage is calculated from the predetermined time value and the integrated voltage value at that time until the predetermined voltage is reached. A prediction calculation means for predicting calculation of the time.

(14) The camera according to (13), wherein the setting of the predetermined time can be changed according to the shooting mode of the camera. (15) The camera according to (13), wherein the predetermined time can be reset according to a subject luminance.

(16) In a camera having a photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined value. If the integration voltage of the integration capacitor does not reach the predetermined value even after a predetermined time has elapsed from the start of the integration, the brightness calculation means for calculating the subject brightness data based on the integration voltage at that time is provided. A photometric device, comprising:

(17) The camera according to (16), wherein the setting of the predetermined time can be changed according to a shooting mode of the camera. (18) The camera according to (16), wherein the predetermined time can be reset according to a subject luminance.

[0070]

As described above, according to the present invention, it is possible to provide an easy-to-use photometric device without increasing the release time lag even if the subject has low luminance.

[Brief description of the drawings]

FIG. 1 is a block diagram of a camera having a photometric device according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating an operation of the photometric device, in which FIG. 2A is a timing chart illustrating an operation when the subject brightness is not low and the brightness is normal, and FIG. It is a flowchart explaining an operation.

FIG. 3 is a flowchart illustrating a photometry operation according to the first embodiment.

FIG. 4 is a flowchart illustrating an example of a time _limit setting operation of a photometric device according to a second embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation of performing re-photometry according to a subject luminance in the third embodiment of the present invention.

[Explanation of symbols]

 1 CPU, 2 AF IC, 3 IRED, 4 PSD, 5 Emitter / Receiver, 6 EEPROM, 7 Interface, 8 Power Supply Stabilizing Circuit, 9 Motor Driver, 10 Plunger Driver, 11 Film Feeding Motor, 12 Photographing Lens Drive motor, 13, 14, 16 encoder, 15 plunger, 17 DX circuit, 18 strobe unit, 19 liquid crystal display panel, 20 date imprinting circuit, 21 reset IC, 22 first release switch (R1SW), 23 second release switch (R2SW), 24 strobe mode switch (FLSSW), 25 self-timer switch (SLSW), 26 forced rewind switch (RWMSW), 27 barrier switch (BRSW), 28 back cover switch (BKSW), 29, 30 , 31 light emitting diode, 32 photodiode, 33 integrating capacitor, 34 A / D conversion circuit, 35 integrating transistor.

Claims (3)

[Claims] 1. An integrating capacitor for integrating a photocurrent according to the amount of incident light, a detecting means for detecting a voltage of the integrating capacitor, a time measuring means for measuring a measuring time from the start of integration of the integrating capacitor; If the integrated voltage has reached a predetermined voltage value before the measurement by the means has passed a predetermined time, subject brightness data is calculated based on the time measurement data of the time measurement means, and before the integrated voltage reaches the predetermined voltage value. And a calculating means for calculating the subject brightness data from the predetermined voltage value, the predetermined time, and the voltage value detected by the detecting means when the predetermined time has elapsed. 2. A photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined voltage value. If the integrated voltage of the integrating capacitor does not reach the predetermined value even after a predetermined time has elapsed since the start of the operation, the time required to reach the predetermined voltage from the predetermined time value and the integrated voltage value at that time is determined. A photometric device, comprising: a prediction calculation unit that performs a prediction calculation; and a luminance calculation unit that calculates subject brightness data based on the time calculated by the prediction calculation unit. 3. A photometric device that integrates a photocurrent output from a light receiving element with an integrating capacitor and outputs subject luminance data based on time data until the integrated voltage reaches a predetermined voltage value. If the integrated voltage of the integrating capacitor does not reach the predetermined voltage value even after a predetermined time has elapsed from the start of the process, a brightness calculating means for calculating the subject brightness data based on the integrated voltage at that time is provided. A photometric device, characterized in that: