JP2000275695A - Camera exposure control device and camera exposure control method - Google Patents

Abstract

(57) [Summary] [Problem] To always obtain an appropriate exposure even when a selected aperture is changed to another aperture. SOLUTION: The aperture amount is sequentially controlled based on each aperture value of a plurality of combinations of a predetermined aperture value and a time value,
A correction time value corresponding to each controlled aperture amount is obtained and held, and when the aperture value of the selected combination is forcibly changed under predetermined conditions, the held correction time value is obtained. Using the time value, the time value corresponding to the aperture value of the change destination is corrected. It is possible to correct the error of the time value caused by the variation of the aperture for each solid, to avoid improper exposure, and to obtain a captured image with good image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera exposure control device and a camera exposure control method, and more particularly, to a program type camera exposure control device and a camera exposure control method.

[0002]

Proper exposure of the Related Art In general camera, B the luminance of the object, the sensitivity of the photosensitive material S, the exposure time T, if the brightness of the lens and ^{1 / F 2, BS · T} / F 2 = K or F ² / T = BS / K (1) In the equation (1), K is a constant, and F is a so-called F number. The F number is the ratio (D / f) of the effective aperture D of the photographic lens to the focal length f.
(F / D). It is called an F number to distinguish it from the focal length f.

In a case where an ideal image is formed on an object at infinity like a normal photographic lens, if the transmittance of the lens and the luminance of the object are fixed, the illuminance of the image on the optical axis becomes the F number. Inversely proportional to the square (F ² ) (ie, proportional to 1 / F ² )
I do. The series of F number is JIS7106-196
0, a sequence of common ratio √2 through 1 according to ASA PH 3.33-1967 (0.5000 0.7071 1.0
00 1.414 2.000 2.828 4.00
0 5.657 8.000 11.31 16.00
22.63 32.00 45.25...), Which is generally abbreviated to this value (0.5 0.7
1 1.4 2.0 2.8 4 5.6 8 11
16 22 32 45...). When the aperture needs to be subdivided, for example, when dividing into two, a geometric progression of ⁴の 2 that passes through 1 is used, and when dividing into three, 1 is used when dividing into three.
Although it selected from geometric progression of ⁶ √2 through, herein order to avoid complication of the description, unified sequence of the common ratio of √2.

As can be understood from the equation (1), the exposure control elements of the camera include the exposure time T and the lens brightness 1 / F.
^Two of two. T is the shutter speed of the camera, 1 / F ²
Corresponds to the amount of aperture of the camera, and the camera exposure control device controls T and 1 / F ² to appropriate values in accordance with the brightness B of the subject. Now, when F ² , 1 / T and F ² / T are expressed by equations (2) to (5) as exponential functions each having a base of 2, the exponents Av, Tv, and Ev are each represented by an aperture value (Aper
time Value), time value (Time Value)
e) and Exposure Value. F ² = 2 ^Av (2) 1 / T = 2 ^Tv (3) F ² / T = 2 ^Ev = 2 ^{(Av + Tv)} (4) Ev = Av + Tv ... (5)

[0005] Also, photosensitive material sensitivity NS, subject brightness B / NK, and photographic brightness BS / K, which are related to brightness, are used.
As exponential functions each having a base of 2,
When expressed by the equation (9), the indices Sv, Bv, and Lv are respectively represented by a sensitivity value (Film SpeedValue), a luminance value (Luminance Value), and a light value (Lig).
ht Value). NS = 2 ^Sv ... (6) B / NK = 2 ^Bv ... (7) BS / K = 2 ^Lv = 2 ^{(Sv + Bv)} ... (8) Lv = Sv + Bv ...・ (9)

The sensitivity value Sv, the luminance value Bv and the light value Lv are
It has the same properties as the above-described aperture value Av, time value Tv, and exposure value Ev, and can be expressed as in equation (10). Av + Tv = Ev = Lv = Sv + Bv (10) Therefore, the exposure value Ev is given by the sum of the opening value Av and the time value Tv, and the proportion of the exposure value is arbitrary. Or E
Since v = Lv, the exposure value Ev is also given by the sum of the sensitivity value Sv and the luminance value Bv, and the proportion is similarly arbitrary.

[0007] As described above, the system for calculating the exposure by addition and subtraction of Av and Tv or Sv and Bv is an APEX system (Additive System of Photo).
graphic Exposure). APEX
One of the methods is called a program expression. This is an exposure control mode in which a combination of the aperture value Av and the time value Tv is predetermined (programmed) for each Ev value (exposure value), and a chart for representing the combination is “ This is called a “program diagram”.

FIG. 6 is an example of a program chart. In the figure, the horizontal line indicates the aperture value Av, the vertical line indicates the time value Tv, and the oblique line indicates the exposure value Ev. In the figure, the Av value is represented by the F number for convenience, and the Tv value is represented by the shutter speed (second time) for convenience, but the conversion from the F number to the Av value is performed before. Expression (2) may be used, and the conversion from the shutter speed to the Tv value may use Expression (3). In FIG. 6, if the Ev value is, for example, “11”,
An aperture value Av and a time value Tv for obtaining an appropriate exposure are given by a combination of Av and Tv located at each intersection indicated by a circle in the figure. If the upper and lower limits of Av and Tv are ignored, F2.8 is obtained.
And 1/250, F4 and 1/125, F5.6 and 1/6
0, F8 and 1/60, F11 and 1/15, F16 and 1 /
8, Ev = 11 in any combination of F22 and 1/4
The proper exposure to is obtained.

However, since the actual camera Av value and Tv value have upper and lower limits, for example, the effective range of the Av value is F4
To F11, and the effective range of the Tv value is 1/30 to 1/25.
If it is set to 0, the actual appropriate exposure control range is the range of the broken line in FIG. 7, and the Ev lines (9 to 15 in the figure) intersecting each intersection within this range are the subject brightness that can be photographed.

FIG. 8 is a flowchart of a conventional exposure control process. This flowchart is executed when the shutter button of the camera is half-pressed. When the flowchart is executed, first, the counter variables i and j are set to 1 and initialized (S1), and then the luminance Ev of the subject is measured using an exposure meter (S2). Next, Av is given by Av _(i)
Is set (S3), and Tv _(j) is set in Tv (S4). Here, Av _(i) and Tv _(j) are data of a table held in a memory inside the camera in advance, and the structure of the table is, for example, as shown in Tables 1 and 2 below. I have.

[0011]

[Table 1]

[0012]

[Table 2]

In Tables 1 and 2, when i = 1 and j = 1, Av ₍₁₎ = F4 and Tv ₍₁₎ = 1/250, so that Av is set to = F4 and Tv 1/250
Is set. Next, it is determined whether or not Ev = Av + Tv. If the determination is YES, the aperture control (S6) and the shutter speed setting are performed using the values of Av and Tv (F4 and 1/250) set in S3 and S4. (S7) is performed and the flowchart ends, but if the determination is NO, the following loop processing is executed.

First, it is determined whether or not j = 4 (S
8). That is, the last record (Tv
₍₄₎ It is determined whether or not) has been reached. If it has not been reached, j is counted up (S9), and S4 and subsequent steps are repeated. Thereby, Tv stored in the table of Table 2 is obtained.
₍₁₎ to Tv The values of ₍₄₎ are sequentially extracted and set to Tv. If Ev = Av + Tv is determined during the repetition, the aperture control and the shutter speed setting are performed using the values of Av and Tv set in S3 and S4 during the repetition, and the flowchart ends.

On the other hand, even when j = 4, Ev = Av + Tv
Is not determined, j is set to 1 (S11).
At the same time, i is counted up (S12), and S3 and subsequent steps are repeated until i = 4 (YES determination in S10).
Assuming that the Ev value is in the range of 9 to 15, Ev = Av + Tv will be determined in any of the above-described repetitive processes, and aperture control and shutter speed setting will be performed using the Av value and Tv value at the time of determination. Therefore, shooting can be performed under appropriate exposure conditions that satisfy Ev = Av + Tv. Table 1
And all combinations of the tables in Table 2
If v = Av + Tv is not determined, for example, E
It is determined that the v value is too small (too dark), and a flash light emission process or the like (S13) is performed.

By the way, since the opening degree of the aperture mechanism of each camera and the opening / closing amount of the shutter mechanism are inevitable and the adjustment work at the time of completing the assembly is indispensable, the tables shown in Tables 1 and 2 have conventionally been used. Although the opening amount of the aperture mechanism and the opening and closing amount of the shutter mechanism of each camera were adjusted to accurately correspond to the above data, some adjustment errors were included because it was impossible to completely adjust . For example,
The opening amount of the aperture mechanism may include an error of up to ± 0.3 Ev in Ev value conversion. Now, the above error will be described using two adjacent data in Table 1 as examples, for example, F4 and F5.6. When performing aperture control using Av _{(1) in the} table, the opening amount of the aperture mechanism is Av ₍₁₎ = F4, but if there is an error of −0.3 Ev, the opening corresponding to Av ₍₁₎ = F4 tends to be slightly larger than F4. When the aperture control is performed using Av _{(2) of the} table, the opening amount of the aperture mechanism is Av ₍₂₎ = F5.
6, but when there is an error of +0.3 Ev, the opening amount corresponding to Av ₍₂₎ = F5.6 tends to be slightly closed compared to F5.6.

FIG. 9 shows the above error on a program diagram, and solid lines 1 and 2 indicate ideal openings corresponding to data (ie, Av ₍₁₎ and Av ₍₂₎ ) on the table. Degrees and broken lines 3 and 4 are actual opening degrees including errors. As described above, the exposure control device performs the proper exposure condition (Ev = Av +
Av and Tv that satisfy Tv) are selected. The error of the selected Av can be absorbed by the operation of the exposure control device.

[0018]

However, for example, when a process of forcibly changing a selected Av to another Av such as backlight correction is performed, nEv is converted into an Ev value.
In order to change the opening amount of the aperture mechanism in units (n is 1, 2, 3,...), If there is an error as shown in FIG.
If it is set to 1, the opening amount is changed from the broken line 3 to the one-dot chain line 5 on 1Ev, and the Tv value is originally T '.
Is T "where it should be, and as a result,
There has been a problem that the proper exposure is deviated by the time difference ΔT between T ′ and T ″. Therefore, the problem to be solved by the present invention is to change the selected aperture to another aperture. The goal is always to get the right exposure.

[0019]

SUMMARY OF THE INVENTION The present invention provides a camera for selecting one of a plurality of combinations of predetermined aperture values and time values to set an aperture amount and a shutter speed suitable for the brightness of a subject. In the exposure control device, the aperture amount is sequentially controlled based on each aperture value of the combination, and a correction time value corresponding to each aperture amount controlled by the control means is obtained and held, and the selected correction time value is selected. When the aperture value of the combination is forcibly changed under a predetermined condition, the time value corresponding to the aperture value to be changed is corrected using the held correction time value.

More specifically, according to the first aspect of the present invention, one of a plurality of combinations of a predetermined aperture value and a time value is selected, and an aperture amount and a shutter speed suitable for the brightness of the subject are selected. In a camera exposure control device to be set, a control means for sequentially controlling the aperture amount based on each aperture value of the combination, and a correction time value corresponding to each aperture amount controlled by the control means are obtained. Holding means for holding. Alternatively, the invention according to claim 2 is the invention according to claim 1, wherein the changing means for forcibly changing the aperture value of the selected combination under predetermined conditions;
When the opening value is changed by the changing unit, a correcting unit that corrects a time value corresponding to the opening value to be changed using the correction time value held in the holding unit. And Alternatively, in the invention according to a third aspect, in the invention according to the second aspect, the changing means converts the aperture value of the selected combination into nEv units (n
Is changed to 1, 2, 3,...). According to a fourth aspect of the present invention, there is provided an exposure control for a camera, wherein one of a plurality of combinations of a predetermined aperture value and a time value is selected to set an aperture amount and a shutter speed suitable for the brightness of a subject. The method is characterized in that the aperture amount is sequentially controlled based on each aperture value of the combination, and a correction time value corresponding to each aperture amount is obtained and held. Alternatively, in the invention according to claim 5, in the invention according to claim 4, when the aperture value of the selected combination is forcibly changed under predetermined conditions, the held correction time value is changed. And correcting the time value corresponding to the aperture value of the change destination.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, taking an electronic still camera as an example. In FIG. 1, reference numeral 10 denotes a photographic lens, 11 denotes an aperture mechanism provided on the optical axis of the photographic lens 10, 12 denotes a driving unit of the aperture mechanism 11, and 13 denotes an image pickup signal of a subject by receiving light passing through the aperture mechanism 11. Image sensor (hereinafter C)
CD), 14 is a driver for the CCD 13, 15 is the CCD 1
3, a timing generator for generating various timing signals such as a signal for controlling an imaging time (electronic shutter time: hereinafter, simply referred to as a shutter time); 16 samples an imaging signal from the CCD 13 to remove noise The sample-and-hold circuit 17 is an analog-to-digital converter that converts the image signal after noise removal into a digital signal.

Reference numeral 18 denotes a digital-to-analog converter 1
7, a color processing circuit for generating a combined luminance / color difference signal (hereinafter referred to as a YUV signal) from the output of 7, a video transfer circuit 19, a buffer memory 20 for holding a sequentially generated YUV signal, and a recording memory 21 for the YUV signal And a compression / expansion circuit for performing compression / expansion processing by a predetermined encoding method (generally, JPEG method) at the time of reproduction, 22 is a photometric sensor for measuring the brightness of the subject, and 23 is a fixed or detachable recording the compressed YUV signal. A possible flash memory.

Reference numeral 24 denotes a control program stored in the program ROM 24a to execute control of recording and reproduction of an image and various controls accompanying these controls (for example, one of them is an exposure control, and 24b is an exposure control. The EEPROM is a CPU that holds the correction data necessary for (1) and the table data of Table 1 and Table 2). The CPU 24 has a function as a control unit, a change unit, and a correction unit described in the gist of the invention, and
b corresponds to the holding means described in the gist.

A key input unit 25 generates a key input signal in response to operation of a shutter button or various buttons.
26, a digital video encoder for converting the YUV signal held in the buffer memory 20 into a signal format suitable for display; 27, a liquid crystal display for an image monitor for displaying a signal from the digital video encoder 26;
Reference numeral 28 denotes a bus for connecting each unit.

The electronic still camera having such a configuration can be switched between the factory adjustment mode and the normal user operation mode by operating a predetermined key on the key input unit 25. The factory adjustment mode is a mode for measuring the variation of each of the assembled electronic still cameras, and is, for example, a mode for collecting correction data for obtaining an appropriate exposure in exposure control.

FIG. 2 is a block diagram when the above-described collection mode is executed. Numeral 30 denotes an electronic still camera, and numeral 31 denotes a light source of a known amount of light installed at a fixed distance in front of the electronic still camera 30. FIG. 3 is a schematic flowchart showing a program in the collection mode. This program is one of control programs executed by the CPU 24.
When the program of FIG. 3 is started, first, the counter variable i
Is set to 1 (S20), and the light source 31 is turned on (S20).
21). Next, the data of Av _(i) (Av ₍₁₎ = F4) is looked up from the table (see Table 1) held in the EEPROM 24b, and this lookup data (F4) is used. The opening amount of the aperture mechanism 11 is controlled (S22). Next, the luminance Ev of the light source 31 is measured from the output of the photometric sensor 22, and Ev = Av ₍₁₎
The value of Tvadj ₍₁₎ satisfying + Tvadj ₍₁₎ is obtained, and the value is stored in a predetermined area of the EEPROM 24b in association with Av ₍₁₎ (S23).

Next, it is determined whether or not i = 4 (S24). Since i = 1 at present, the count is increased to i = i + 1 = 2 (S25), and then step S22 is performed again.
Repeat thereafter. That is, since i = 2, EE
From the table held in the PROM 24b, Av ₍₂₎
(F5.6; see Table 1), and using the lookup data (F5.6), the diaphragm mechanism 1
1 is controlled (S22). Next, the luminance Ev of the light source 31 is measured from the output of the photometric sensor 22, and Ev = A
v ₍₂₎ + Tvadj ₍₂₎ The value of Tvadj ₍₂₎ that satisfies ₍₂₎ is obtained, and the value is associated with Av _{( 2)} and the EEPROM 24 b
(S23).

Next, the data is counted up to i = i + 1 = 3 (S25), and the data of Av ₍₃₎ (F8; see Table 1) is looked up from the table held in the EEPROM 24b. The opening amount of the throttle mechanism 11 is controlled using F8) (S22). Next, the luminance Ev of the light source 31 is measured from the output of the photometric sensor 22, and Tvad that satisfies Ev = Av ₍₃₎ + Tvadj ₍₃₎
obtains the value of j _(3), EEP associates that value Av ₍₃₎
It is stored in a predetermined area of the ROM 24b (S23).

Next, the data is counted up to i = i + 1 = 4 (S25), and the data of Av ₍₄₎ (F11; see Table 1) is looked up from the table held in the EEPROM 24b. The opening amount of the aperture mechanism 11 is controlled using F11) (S22). Next, the brightness Ev of the light source 31 is measured from the output of the photometric sensor 22, and Tva that satisfies Ev = Av ₍₄₎ + Tvadj ₍₄₎
dj ₍₄₎ is obtained, and the value is associated with Av ₍₄₎ and EE
After storing in a predetermined area of the PROM 24b (S23), i = 4 is determined in step S24, and the program ends. As a result of the above program processing, the EEPROM 24b
The correction data shown in the following Table 3 is stored in the predetermined area.

[0030]

[Table 3]

In Table 3, t1 is correction data associated with Av ₍₁₎ , t2 is correction data associated with Av ₍₂₎ , t3 is correction data associated with Av ₍₃₎ , and t4 is Av _{(1). This} is the correction data associated with ₄₎ . t1 to t4 represent the respective opening values when the aperture value of the diaphragm mechanism is changed to F4, F5.6, F8, and F11 using the light source 31 of a known light amount. If the obtained time difference ΔT is set to zero (T ′ = T ″), that is, if the adjustment error of the opening amount of the throttle mechanism is set to zero, t1 = Tv ₍₁₎ , t2 = Tv ₍₂₎ , and t3 = T.
v ₍₃₎ and time value data satisfying t4 = Tv ₍₄₎ .

As described at the beginning, since the adjustment error of each camera is about ± 0.3 Ev at the maximum, t1 to t4 and T4
v _{(1) to} Tv ₍₄₎ do not match. Therefore, t1 ≠ Tv
₍₁₎ , t2 ≠ Tv ₍₂₎ , t3 ≠ Tv ₍₃₎ , t4 ≠ Tv ₍₄₎ , and the difference between t1 and Tv ₍₁₎ , the difference between t2 and Tv ₍₂₎ , t3 and Tv ₍₃₎ And the difference between t4 and Tv ₍₄₎ are the time difference ΔT described in the problem of the conventional example.

Next, a normal user operation mode will be described. This mode includes a through mode in which an image pickup signal periodically taken out from the CCD 13 is converted into a signal suitable for display and sequentially displayed on the liquid crystal display 27, and a shutter mode. A capture mode in which a desired imaging signal is recorded in the flash memory 23 by operating a key can be divided into a capture mode in which a desired image is read from the flash memory 23 and displayed on the liquid crystal display 27. In the through mode, the CCD 13 disposed behind the photographic lens 10 is driven by a signal from the driver 14, and the subject images collected by the photographic lens 10 are photoelectrically converted at regular intervals to output an image signal for one image. Is done. Then, the imaging signal is sampled by the sampling and holding circuit 16 and converted into a digital signal by the analog-to-digital converter 17, and then a YUV signal is generated by the color process circuit 18. This YUV signal is supplied to the video transfer circuit 19
And transferred to the image buffer of the buffer memory 20 via the video transfer circuit 19, after the transfer to the buffer is completed, sent to the liquid crystal display 27 via the digital video encoder 26 and displayed as a through image. .

When the direction of the camera is changed in this state, the composition of the through image displayed on the liquid crystal display 27 changes, and the shutter key is "half-pressed" at an appropriate time (when a desired composition is obtained). After the exposure and focus are set, when the “full press” is performed, the mode switches to the capture mode, and the YUV signal stored in the image buffer of the buffer memory 20 is fixed at the current YUV signal and displayed on the liquid crystal display 27. The through image is fixed at the image at the same point. Then, the Y stored in the image buffer of the buffer memory 20 at that time is
The UV signal is sent to a compression / decompression circuit 21 via a video transfer circuit 19, and is subjected to JPEG encoding for each component of luminance information and color difference information in a unit called a basic block of 8 × 8 pixels. 23
Will be recorded.

In the reproduction mode, the path from the CCD 13 to the buffer memory 20 is stopped, and the latest captured image is read out from the flash memory 23 and decompressed by the compression / decompression circuit 21. Is sent to the image buffer of the buffer memory 20 via the. Then, the data in the image buffer is sent to the liquid crystal display 27 via the video transfer circuit 19 and the digital video encoder 26, and is displayed as a reproduced image.

The control of the opening amount of the aperture mechanism 11 and the charge accumulation time of the CCD 13, that is, the exposure control, is performed in both the through mode period and the capture mode period described above.
The operation of the exposure control will be described with reference to FIG. 7 described above. In short, the aperture value Av and the time value T existing within the broken line frame shown
v of each combination measured by the photometric sensor 22
This is an operation of selecting one combination that satisfies the value v and has the time value Tv as fast as possible in consideration of camera shake prevention. For example, if the Ev value is “11”, then Av =
4. A combination of Tv = 1/250 is selected, and in the capture mode, the image is recorded with this combination fixed.

In the case where the background of the subject includes the sun or illumination, the Ev value increases due to the influence of the bright light, and as a result, the subject appears dark. Therefore, when there is a high-luminance portion around the subject, it is determined that backlight shooting has been performed, and the Av value of the selected combination is converted to an Ev value by nEv (n is 1, 2,...). The backlight correction is forcibly changed.

However, if the selected Av is forcibly changed to another Av, there is an error in the opening amount of the aperture mechanism, for example, an error as shown in FIG.
When the opening amount is changed aiming at the one-dot chain line 5 on v,
Where the Tv value should originally be T ', it becomes T ". As a result, a problem arises in that the exposure is deviated from the proper exposure by the time difference ΔT between T' and T". Note that such inconvenience is not limited to backlight correction processing. Any processing for forcibly changing the Av value of the selected combination by nEv in Ev value conversion corresponds to this.

In the present embodiment, the above disadvantage is solved.
Therefore, the Av value of the selected combination is converted to Ev value.
When performing the process of forcibly changing only nEv,
Execute the correct processing program. Figure 4 shows the program
FIG. 3 is a diagram showing a schematic flowchart of the above. Figure smell
Thus, CUR and TGT are variables, respectively. program
Starts, first, the Av number of the selected combination
(Av_(i)I); the same applies to the following)
(S30) Further, the Av number of the change destination is set in the TGT.
(S31). Then, change using the following equation (11)
The previous Tv value is calculated. Tv_(TGT)= Tv_(CUR)× Tvadj_(TGT)/ Tvadj_(CUR)  ... (11) where Tv_(CUR)Is the T stored in the table of Table 2 above.
v_(i)And Tvadj_(TGT)And Tva
dj_(CUR)Is Tvadj stored in the table of Table 3 above.
_(i)Data.

For example, when CUR = 1 and TGT = 2,
That is, the Av value of the selected combination is converted to an Ev value.
If you want to forcibly change to the narrowing-down side by 1 Ev in
Equation (11) becomes like the following equation (12). Tv_(TGT) = Tv₍₁₎× Tvadj₍₂₎/ Tvadj₍₁₎  ・ ・ ・ ・ (12) From Table 2 above, Tv₍₁₎= 1/250, for convenience
If ΔT = 0, Tvadj₍₁₎= 1/250 =
0.004 [sec], Tvadj₍₂₎= 1/125 = 0.
008 [sec], and the previous equation (12)_(TGT)= 0.004 × 0.008 / 0.004 (13) where Tv is the change destination_(TGT)Is Tv₍₂₎1/1 of the same value as
25, but if ΔT ≠ 0, the Tv_(TGT)
Is Tv₍₂₎To "Tvadj_(TGT)/ Tvadj_(CUR)"so
It becomes the corrected value. For example, Tvadj_(CUR) = 0.0
03 [seconds], Tvadj_(TGT) = 0.009 [sec]
Tv_(TGT)= 0.004 × 0.009 / 0.003 (14), and the destination Tv_(TGT)Is Tv₍₂₎Slower than
0.012 [second]. That is, "Tvadj
_(TGT)/ Tvadj_(CUR)FIG. 5
As shown in FIG._(TGT)Can change position
And This movement amount is ΔT described in the conventional problem.
And “Tvadj”_(TGT)/ Tvadj
_(CUR)To eliminate the effect of ΔT.
Can be.

This will be described. Now, at the time of the error _{measurement, Av (i) + ΔAv (} i) adj: narrow the Av _(i) and the actual aperture value ΔAv when _(i) adj is the aperture when the error _{Av (i + 1) + ΔAv} ( _{i + 1)} adj: actual aperture value when the aperture is Av _{(i + 1)} ΔAv _{(i + 1)} adj is the aperture error at that time Tv _(i) adj: aperture Av _(i) + ΔAv _{(i )} Exposure time for adj Tv _{(i + 1)} adj: Aperture Av _{(i + 1)} + ΔAv _{(i + 1)} adj
Under the light source having a constant luminance, from the appropriate exposure condition expression of the above expression (1), (Av _(i) + ΔAv _(i) adj) ² / Tv _(i) adj = (Av _{(i + 1)} + ΔAv _{(i + 1)} adj) ² / Tv _{(i + 1)} adj = BS / K = constant (15)

Further, at the time of actual use, Av_(i)+ ΔAv_(i): Aperture is Av_(i)Actual when
Aperture value of ΔAv_(i)Is the aperture error at that time Av_{(i + 1)}+ ΔAv_{(i + 1)}: Aperture is Av_{(i + 1)}And when
Actual aperture value of ΔAv_{(i + 1)}Is the aperture error at that time Tv_(i): Aperture Av_(i)+ ΔAv_(i)Exposure time Tv_{(i + 1)}: Aperture Av_{(i + 1)}+ ΔAv_{(i + 1)}Exposure to
Assuming that the time is, from the appropriate exposure condition expression of the above expression (1), (Av_(i)+ ΔAv_(i))^Two/ Tv_(i)  = (Av_{(i + 1)}+ ΔAv_{(i + 1)})^Two/ Tv_{(i + 1)} (16)

The aperture is set to Av_(i)And Av_{(i + 1)}Fruit when
(Av_(i)+ ΔAv_(i)adj)^Two/ (Av_{(i + 1)}+ ΔAv_{(i + 1)}adj)^Two  = (Av_(i)+ ΔAv_(i))^Two/ (Av_{(i + 1)}+ ΔAv_{(i + 1)})^Two ... (17), the aperture value is 2^{(x / 2)}In geometric series
2 ＾ (Av_(i)+ ΔAv_(i)adj) / 2 ＾ (Av_{(i + 1)}+ ΔAv_{(i + 1)}adj) = 2 ＾ (Av_(i)+ ΔAv_(i)) / 2 ＾ (Av_{(i + 1)}+ ΔAv_{(i + 1)}(18) where ＾ represents an exponent (the same applies hereinafter). Therefore, 2 ＾ ΔAv_(i)adj / 2 ＾ ΔAv_{(i + 1)}adj = 2 ＾ ΔAv_(i)/ 2 ＾ ΔAv_{(i + 1)} ・ ・ ・ ・ (19) Therefore, ΔAv_(i)adj-ΔAv_{(i + 1)}adj = ΔAv_(i)-ΔAv_{(i + 1)} ... (20) From the equations (15) and (16), the equation (20) is
When standing, Tv_{(i + 1)}= Tv_(i)× (Av_{(i + 1)}+ ΔAv_{(i + 1)})^Two/ (Av_(i)+ ΔAv_(i))^Two  = Tv_(i)× Av_{(i + 1)}adj^Two/ Av_(i)adj^Two  = Tv_(i)× Tv_{(i + 1)}adj / Tv_(i)adj... (21) Therefore, the ratio of the error measurement data
(Tv_{(i + 1)}adj / Tv_(i)adj) to change to
Time value Tv_{(i + 1)}Can be corrected.

As described above, according to the present embodiment, even if the Av value of the selected combination is forcibly changed by nEv in terms of the Ev value, it can be corrected to an appropriate Tv value. This provides a special effect that a captured image with good image quality can be obtained by avoiding inappropriate exposure.

In the above embodiment, an example of application to an electronic still camera has been described. However, the present invention is not limited to this. The present invention can be applied to all cameras including a silver halide camera as long as it performs a program-type exposure control.

[0046]

According to the present invention, a camera exposure for selecting one of a plurality of predetermined combinations of aperture values and time values and setting an aperture amount and a shutter speed suitable for the brightness of a subject. In the control device, the aperture value is sequentially controlled based on each aperture value of the combination, a correction time value corresponding to each controlled aperture value is obtained and held, and the aperture value of the selected combination is adjusted. When forcibly changing under a predetermined condition, the time value corresponding to the aperture value to be changed is corrected using the held correction time value, so that the aperture of each solid is adjusted. The improper exposure can be avoided by correcting the time value error caused by the variation, and a captured image with good image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a configuration diagram during error measurement.

FIG. 3 is a flowchart of an error measurement program.

FIG. 4 is a flowchart of an exposure correction program.

FIG. 5 is an operation explanatory view of the embodiment.

FIG. 6 is a program diagram when the upper and lower limits of Av and Tv are not considered.

FIG. 7 is a program diagram when upper and lower limits of Av and Tv are considered.

FIG. 8 is a flowchart of an exposure control program.

FIG. 9 is a diagram for explaining inconvenience of a conventional example.

[Explanation of symbols]

 24 CPU (control means, change means, correction means) 24b EEPROM (hold means)

Claims (5)

[Claims] 1. An exposure control apparatus for a camera, wherein one of a plurality of combinations of a predetermined aperture value and a time value is selected to set an aperture amount and a shutter speed suitable for the brightness of a subject. Control means for sequentially controlling the aperture amount based on the combined aperture values; andholding means for obtaining and holding a correction time value corresponding to each aperture amount controlled by the control means. Characteristic exposure control device for camera. 2. A change means for forcibly changing an aperture value of a selected combination under predetermined conditions, and a correction means held in said holding means when the aperture value is changed by said change means. 2. The exposure control device for a camera according to claim 1, further comprising: a correction unit configured to correct a time value corresponding to the aperture value to be changed using the time value. 3. The changing means converts the aperture value of the selected combination into nEv units (n = 1, 2,
The exposure control device for a camera according to claim 2, wherein the change is made to (3, ...). 4. An exposure control method for a camera, wherein one of a plurality of predetermined combinations of aperture values and time values is selected to set an aperture amount and a shutter speed suitable for the brightness of a subject. An exposure control method for a camera, comprising: sequentially controlling an aperture amount based on each aperture value of a combination; obtaining and holding a correction time value corresponding to each aperture amount; 5. When the aperture value of the selected combination is forcibly changed under predetermined conditions, a time value corresponding to the aperture value to be changed is set using the held correction time value. The exposure control method for a camera according to claim 4, wherein the correction is performed.