JP2584656C - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial applications)   The present invention relates to a so-called program automatic exposure control device.
Not only can you get a correct exposure, but you can also get better quality images
The present invention relates to an exposure control device capable of performing the following. (Conventional technology)   Determine exposure by appropriately combining aperture and shutter speed according to the brightness of the subject
So-called automatic exposure control device (hereinafter abbreviated as exposure control device)
Sometimes. ) Can be very simple to take photos,
Used in most cameras. Taking an example of an interchangeable lens camera
A brief description of the conventional exposure control device is as follows.   Conventional devices of this type use a combination of an aperture and a shutter speed to obtain an appropriate exposure.
There are multiple program diagrams to determine the alignment. FIG. 4 shows such a program. FIG. 3 is a diagram showing a system diagram, in which P₁, P_TwoAnd P_ThreeThree types of programs indicated by
FIG. 3 shows an example with a diagram.   In the case shown in FIG._TwoConsider the program diagram shown as standard
And P₁In the program diagram shown by, the shutter speed is increased at the same object brightness.
It can be said that it is possible to shoot in the state where_ThreeThe program diagram shown by
It can be said that shooting can be performed in a state where the focus is narrowed down at one subject luminance.   Which of these program diagrams should be used for exposure control?
Selection depends on the focal length of the interchangeable lens (photography lens) used for photography.
If the taking lens is a zoom lens, it changes according to the rotation of the zoom ring.
It was done by the focal length. That is, in the example of FIG. 4, the focal length is
A certain value f₁P for all longer₁Is used, and the focal length is f
_TwoIf shorter (however, f_Two<F₁) Is all P_ThreeThe program diagram shown by is used.
Other than P_TwoThe program diagram shown by was used. (Problems to be solved by the invention)   However, when taking a picture, the shutter speed at that time is used.
The camera shake limit speed value determined by the reciprocal of the focal length of the shooting lens (however, the dimension is ignored.
When the focal length f is 50 mm, the shutter speed is 1/50 second. ) Faster speed
It is said that shooting errors are less likely to occur due to camera shake. In this regard,
The conventional exposure control device has a program diagram for each of various types of photographing lenses having different focal lengths.
It does not mean that there is a zone.
Since the ram diagram is assigned, the shutter speed in the program diagram is the slowest.
Point (rise shutter speed, T in Fig. 4)_V1, T_V2And T_V3Point).
For example, a common factor value for a plurality of photographing lenses to which the program diagram is applied must be used.
For this reason, there is a case where the performance of each photographing lens cannot be sufficiently exhibited.   The present invention has been made in view of such a point, and accordingly, an object of the present invention.
Not only can obtain the proper exposure amount, but also can obtain images with better image quality.
It is an object of the present invention to provide an exposure control device capable of controlling the exposure. (Means for solving the problem)   To achieve this object, according to the present invention, a program diagram for exposure control is provided.
Is determined for each shooting lens with a different focal length.
Up shutter speed T_vfAccording to the focal length f of the taking lens,_vf= Log
_Twof in an exposure control device comprising means for obtaining   The T_vfMeans for obtaining the focal length information of the photographing lens.
Lens ROM and an EA register that is a CPU and functions as a 16-bit register.
Registers, registers B and C, each of which is an 8-bit register,
RAM with data and T_vfThe program that operates the means for determining
A ROM having a CPU having comparison means and arithmetic means,   Information indicating the focal length of the photographing lens stored in the lens ROM is stored in the EA
Take in   The number of digits of the most significant bit of the focal length information stored in the EA register_Two
It is a means for setting the value of the integer part of f. (Action)   According to such a configuration, for each taking lens having a different focal length, and
In the case of a zoom lens, the camera shake limit every time the focal length changes due to zooming
Appropriate rising shutter speed T that does not cause a field_vfTo find the
The program chart that best fits each photographing lens is determined. (Example)   Hereinafter, an exposure control device according to the present invention is an interchangeable lens camera,
) This is an example in which the camera is equipped with a function and includes a shooting lens with a built-in lens ROM.
explain. Explanation of camera configuration   First, the configuration of the above-described interchangeable lens camera will be described with reference to the drawings. still,
The drawings used in the description are only schematically shown to the extent that the present invention can be understood,
The dimensions, shapes, and arrangement of the components are not limited to the illustrated example.
it is obvious. In each figure, the same reference numerals are given to the same components.
Is shown.   FIG. 2A is a block diagram schematically showing the camera.   In FIG. 2A, reference numeral 31 denotes a camera body. 11 is this camera body
A photographing lens attached to 31 is shown, and this example shows a single-focus photographing lens.   The taking lens 11 includes a lens 13 that is movable along the optical axis and contributes to focusing.
Lens system 15 and the driving force from the driving source on the camera body 31 side to the movable lens 13
And a driving force transmission mechanism 17. Further, the taking lens 11 is provided with an aperture of the taking lens.
A lens ROM (Read Only Memory) 19 storing value information, focal length information, etc.,
A lens-side electrical contact group for electrically connecting the photographing lens 11 and the camera body 31
21 is provided.   On the other hand, the camera body 31 includes a main mirror 33, a sub-mirror 35, a focus plate 37, and a pen.
An optical system such as an antenna prism 39, an imaging unit 41 contributing to automatic focusing, and a photographing lens
A drive mechanism 43 for driving the movable lens 13 in the camera 11 and an AE (automatic exposure control).
) And a light receiving element 47 for TTL dimming when using a strobe,
A central display 49 for displaying the status of the camera, and a file for displaying the status of AF and AE.
Display 51 inside the camera, built-in flash 53, and film winding and rewinding
Motor 55 and a body-side electrical contact corresponding to the lens-side electrical contact group 21
A point group 57, a release switch 59, and an X contact 61 as a synchro contact are provided.
I can.   Furthermore, the camera body 31 is a microcomputer that controls the central display unit 49.
Interface and system between IPU (Indi-cation Processing Unit) 71 and imaging unit 41
Control of sequence motor 55 and AF motor 43,
Control and E^TwoPCU (Power Control Unit) 73 with PROM 73a and photometry
DPU (Data Proc), which is a microcomputer that performs calculations and controls the display 51 in the viewfinder, etc.
essing Unit) 75 and CPU (Central Processing Unit)
) 77. The CPU 77 includes an IPU 71, a PCU 73, a DPU 75, and a photographing lens.
The lens ROM 19 in the lens 11 is controlled.   In the camera having the configuration shown in FIG.
Information indicating the focal length of the photographic lens is provided to the CPU 77 via the electrical contact groups 21 and 57.
Is transmitted to However, when the taking lens is a zoom lens, the focal length is zoomed.
It changes to various values with the ringing. Therefore, the lens in the zoom lens In the zoom ROM 19, information corresponding to the focal length that changes variously due to zooming is reserved.
Stored. This information is then read out as described below.   FIG. 2 (B) shows a zoom lens mountable on the camera body 31 cut along the optical axis.
FIG. In this case, the taking lens 81 is provided on the taking lens 11.
In addition to the constituent components, the zoom ring 83 is fixed to the zoom ring 83 so that it can rotate.
Brush 83a to be moved along with the
And a mcode board 83b. FIG. 2C shows the zoom code plate 83b and the lens
Lens composed of a lens ROM 19, a lens-side electrical contact group 21, and a distance code plate 85.
FIG. 2 is a view showing electric components in the apparatus. In this part, each code plate is actually a cylinder of the shooting lens
It is mounted inside so as to be rounded along its circumference. Fig. 2
(D) shows a zoom formed by a zoom ring 83, a brush 83a, and a zoom code plate 83b.
It is a partial perspective view which expands and shows a room encoder part.   When the photographer rotates the zoom ring 83, the focal length of the photographing lens 81 changes.
However, at this time, the brush 83a is positioned in the longitudinal direction of the zoom code plate 83b shown in FIG.
The direction of the zoom ring 83b stops while the
When stopped, it stops at that position. Place this on the surface of the zoom code plate 83b that contacts the brush 83a.
In the case of a, a extending from the lens ROM 19₁, A_Two, A_ThreeAnd a_Four4 shown by
Wiring pattern is provided. The number of wiring patterns may change due to zooming.
To determine the resolution of the focal length,
It is changed by design and is not limited to this example. These four
One of the wiring patterns, in this case a_FourThe wiring pattern shown with is the ground line.
Have been. Also, other wiring patterns a₁~ A_ThreeAre zoom codes in a predetermined relationship.
The width of the plate increases or decreases in the direction perpendicular to the length of the plate
It is formed so that. On the other hand, as shown in FIG.
B corresponding to the number of turns₁~ B_FourAre the four contacts that are electrically connected to each other
It has four contacts. Various contact shapes can be considered. In this case,
Each contact has a double structure to improve the reliability of the connection. Each contact is a pair
The structure is designed to be in contact with the wiring pattern at the wide area of the corresponding wiring pattern.
Especially b_FourThe contact indicated by is a_FourWiring pattern (earth line) Is in contact with   In such a configuration, the brush 83a is moved with the rotation of the zoom ring 83.
Then, z of the zoom code plate 83b₁In the position (see FIG. 2 (C)), the brush 83a
Each contact and wiring pattern a₁, A_Two, A_ThreeIs connected to a₁And a_TwoIn contact state
, A_ThreeIn a non-contact state. Here, the wiring pattern a₁~ A_ThreeIs inside lens ROM19
And each contact of the brush is connected to the wiring pattern a._FourThrough a
Connected to the₁A at the position₁, A_TwoAnd a_ThreeEach wiring pattern indicated by
The voltage state of the₁~ A_Two(0,0,1) (where 0 is low level)
Le). Also, z_TwoAt position (0,1,0), z_ThreeAt position (1,0,0) and z_FourAt position (0
, 0,0). The electrical signal obtained from this change in voltage state is
It is used as an address of the lens ROM 19 as it is.
, Information corresponding to the focal length information stored in advance can be read. reading
The information indicating the issued focal length is transmitted to the CPU 77 as in the case of the single focus photographing lens.
You. T_vfExplanation of means to find   In the camera having the above-described configuration, the program diagram according to the present invention is not required.
Up shutter speed T_VfAccording to the focal length f of the taking lens,_Vf= Log_Twof
Means (T_VfMay be abbreviated as a means for calculating the lens ROM)
19 and a CPU 77. The CPU 77 has a configuration described below.
It is. FIG. 1A is a block diagram showing functions of the CPU 77. In the figure, 77a
Indicates a ROM, and T_VfIs stored.
77b is a comparison means, 77c is a calculation means, 77d is a RAM, and 77e is an input / output port.
Shown. The CPU 77 communicates with the lens ROM 19, the PCU 73,
Information is exchanged with the DPU 75 and the like. In this case, the RAM 77d is shown in FIG.
As shown in B), EA registers functioning as 16-bit registers and 8
B and C registers which are bit registers and an accumulator Acc
And However, the EA register consists of the EAH register for the upper 8 bits and the lower
It is used for each 8-bit EAL register.   <Log_TwoDescription of approximate calculation of f>   Next, using the above-mentioned RAM 77d, arithmetic means 77c and comparing means 77b, T_VfTo lo
g_TwoAn example in which f is obtained as an approximate calculation result will be described. Note that T_VfAccuracy (resolution)
The approximate calculation processing procedure differs depending on the degree. In this embodiment, T_VfResolution
, Subject brightness in current photography is 1/8 E_VBecause it is required in steps,
An example will be described that is suitable for this. Furthermore, from such a thing, log_Twof
Each bit of the accumulator Acc for performing the approximate calculation is, as shown in FIG.
Each is weighted. FIGS. 1 (D) to 1 (F) show T_vfWork means to determine
9 is a flowchart of the operation of the CPU 77.   The CPU 77 stores information indicating the focal length of the photographing lens stored in the lens ROM 19.
The information is taken into the EA register (step 201). About the information indicating this focal length
As described above, the focal length information of a single focus shooting lens is
For zoom lenses, the focal length specified by zooming is
The corresponding information is captured. In this embodiment, the data stored in the lens ROM 19 is stored.
The information indicating the focal length is stored in a form compressed to 8 bits.
Therefore, when the data is stored in the EA register of the CPU 77, it is transformed into the original integer form.
It is to be stored with the information. Briefly explain this compression and deformation.
It is as follows. The 8-bit information stored in the lens ROM is
2 bits from lower 2^Two, 2^FourAnd the upper 6 bits
Is 2 from the lower side⁰, 2¹, 2^Two, 2^Three, 2^Four, 2^FiveIs a second group of bits with
. Then, transform the integer into the sum of the values of each bit of the second group of bits,
Multiply the product of the values of each bit of the group of bits and apply a predetermined constant to the result.
Multiply by.   Next, information indicating the focal length stored in the EA register from the lens ROM 19 will be described.
Therefore, the data of the upper 8 bits of the EA register, that is, the data of the EAH register is 00H (H
Means hexadecimal notation. (The same applies hereinafter) or not (Step 203). In this comparison
The current focal length of the taking lens is 256 mm (2⁸) You can tell if it is above or below.   If EAH = 00H in step 203, set 08H to the B register.
In both cases, the data of the EAL register is stored in the accumulator Acc (steps 205 and 207).
). If EAH ≠ 00H, set 10H in the B register and accumulate The data of the EAH register is stored in the data Acc (steps 209 and 211).   Next, the data of the B register is decremented by 1 and the value is stored in the B register.
(Step 213). Further, the accumulator Acc is shifted left, that is, the lower bit of Acc is shifted.
From the bit to the upper bit direction by one bit (step 215).
Then, it is determined whether the carry (CY) is 1 or not (step 217). Carry (C
If Y) is 0, the flow returns to step 213 again, and steps 213 and 21 are repeated until CY = 1.
Step 5 is repeated.   CY = 1, that is, the most significant bit of the focal length information stored in the EA register appears
Then, check which digit this bit corresponds to. This number is currently
B register value. The log is_Twointeger of approximation of f
Several values are available in the B register. Next, log_TwoDecimal part of approximation calculation of f (1/8
In order to determine the value of (step), a comparison is made as to whether B <06H (step 219).   In this comparison, if the value of the B register is greater than 6 including 6, the B register
The value obtained by subtracting 6 from the star value is stored in the C register (step 221). Next, EA
Shift the register value to the right, that is, one bit from the upper bit to the lower bit
(Step 223), and then subtracts 1 from the value of the C register.
It is stored in the C register (step 225). Unless C = 0FFH, step 223 is performed again.
And the process of steps 223 and 225 until C = 0FFH, that is, until C = −1.
Is repeated. And when C = 0FFH, that is, 0 bit of EA register
The eye, counting from the most significant digit of the information indicating the focal length stored in the EA register.
When the information of the lower 5 bits is stored, 1 is added to the value of the EA register and this value is
The data is stored again in the EA register (steps 227 and 229).   Next, the value of the EA register is shifted right by one bit. With this shift, EA
The 0th bit of the register contains the maximum information of the focal length stored in the EA register.
The information of the fourth bit in the lower direction counted from the upper digit is stored (step
231). Next, 1 is added to the value of the EA register, and this value is stored again in the EA register.
(Step 233). In steps 229 and 233, the value of the EA register is
By adding 1 each, 1 / 16E_VAnd 1 / 32E_VAmend the digits of
That means log_TwoApproximate calculation of f can be performed with high accuracy. In addition, 4th and 5th bits in the lower direction counting from the most significant digit of the information indicating the point distance information
Is added to each of the values of_VfTo 1/8 E_VCorresponding to the steps
T_VfIf the resolution of
It should be understood that the different bit positions also change.   Next, the value of the EA register is further shifted right by one bit (step 235). This
As a result, by the 0th to 2nd bits of the EA register (more precisely, the EAL register),
g_TwoThe information corresponding to the decimal part (1/8) of the approximation calculation result of f is stored.
. The information of the lower 3 bits of the EAL register, that is, the information of the 0th to 2nd bits is stored in the accumulator Ac.
c (step 237).   On the other hand log_TwoThe integer part of the approximate calculation result of f is the information stored in the B register.
And therefore indicates this information and the decimal part stored in the accumulator Acc
By taking the logical sum with information, log_TwoThis gives an approximate calculation result of f.
To match the information position of the B register with the information position of Acc,
Bits are shifted left (step 239). Then, OR is performed (step 241).
). As a result, log_TwoThe approximate calculation result of f is obtained.   Also, in step 219 during the approximate calculation, if B <06H, then
, B <05H (step 251). In this comparison, B is
If it is greater than 5, including 5, then B is 5, and as a result
The processing from step 229 is executed directly. If B <05H, then B <04
H is compared (step 253). In this comparison, B includes 4
If B is greater than 4, then B is equal to 4.
Execute these processes directly. Thus, when B is 5, the same as when B is 6
A process (steps 229 and 233) for increasing the accuracy of the approximation calculation is performed. Also, B
In the case of 4, the accuracy of the approximate calculation of adding 1 to the fourth bit from the most significant bit is
The process for raising (step 233) is performed.   If it is determined in step 253 that B <04H, the processing from step 237 is directly performed.
Run directly.   Log obtained as described above_TwoThe approximate calculation result of f is
Since this is a commonly referred value, the program line for each taking lens with a different focal length Shutter speed rising point T for determining the figure_VfIt is suitable as. Therefore,
The approximate calculation result of_VfOf course, it does not matter, but in this embodiment,
The approximation calculation result is further subjected to a correction process as described below.   <Log_TwoCorrection of approximate calculation result of f>   log_TwoThe reason why the approximation calculation result of f needs to be corrected is as described below.   In order to obtain good photos in normal photography, the focal length of the taking lens must be
When the distance is short, the depth of field is deep, so the aperture is very close and the shutter speed is increased.
When the focal length is long, the depth of field is shallow and the shutter speed is slowed down by closing the aperture.
It is better to comb. Furthermore, a short focal length shooting lens has a long focal length shooting lens.
The camera is easier to shake due to its shorter overall length than the lens, and when the focal length is long,
It is considered difficult to shake due to the long overall length of the camera. For example, shooting with a focal length of 300mm
Actually, it is not so if the lens is 10 times easier to shake than the 30 mm lens,
The camera shake is less than 10 times. Therefore, if the focal length f is, for example, 24
When using a shooting lens of mm, it is better to set the shutter speed to about 1/24 second.
It is better to take a photo at a faster speed (1/30 second or 1/60 second)
You. Similarly, when using a taking lens with a focal length f of 300 mm, for example,
It is better to take a photo at a slower speed than at approximately 1/300 second.
It sounds good. Therefore, in the case of this embodiment, log_TwoApproximate calculation result of f
Correct according to equation (1), and calculate the correction result for each shooting lens with a different focal length.
Rise shutter speed T in the ram diagram_VfAnd       T_Vf= (Log_Twof) ・ α + β ... (1)   Here, α and β are α <1 and the predetermined focal length f₀For log_Twof₀
= (Log_Twof₀) · A constant determined to satisfy α + β.   In addition, this log_TwoIn this case, the approximation calculating and correcting means of f includes the CPU 77 and the PCU 73
And mainly consists of. The reason for using PCU73 is that the constants α and β in equation (1) are
E provided for PCU73^TwoStore them in PROM 73a, and CPU 77 retrieves these constants as necessary.
This is because the configuration is adopted. α and β are stored in, for example, the program ROM 77 of the CPU 77.
a in advance, and E^TwoOf course, a configuration without using PROM73a is also good, but E^TwoUsing PROM
The advantage that α and β can be easily changed even if the design changes etc. Is obtained.   Hereinafter, f₀= 250mm and log_TwoExplanation about correction of approximation calculation result of f
I do.   First, f₀= Log at 250mm_Two250 = (log_Two250) Satisfies the formula α + β
Α and β are determined. Although α and β can take various values,
In the embodiment, α = 3/4 and β = 2. These values are E^TwoPredetermined address of PROM73a
Is stored in   Then, the subsequent correction processing follows the processing of step 241 shown in FIG. 1 (D).
And is performed as described below.   The CPU 77 is the PCU 73 E^TwoΑ and β stored in PROM 73a are
(Step 243), and then log stored in Acc_TwoUse approximation result of f
Then, the correction calculation of the above equation (1) is executed, and the rising shutter speed T_VfAsk (
Step 245).   Log as above_TwoSpecific example of the effect of the correction processing of the approximate calculation result of f
Will be explained.   … When the taking lens used for taking a picture is f = 250mm, lo
g_TwoThe approximate calculation result of 250 is          250 $ 2⁸= 256, log_Two250 ≒ 8 Becomes And the result corrected according to equation (1) is         T_Vf= 8 × 3/4 + 2 = 8 As a matter of course, the approximate calculation result is equal to the correction value.   … Considering the case where the shooting lens used for shooting is f = 1000 mm,   1000 ≒ 2^Ten= 1024, log_Two1000 ≒ 10, but according to equation (1),
As a result, the rising shutter speed is reduced.         T_Vf= 10 x 3/4 + 2 = 9.5   … Considering that the shooting lens used for shooting is f = 30 mm,   30 ≒ 2^Five= 32, log_Two30 ≒ 5, but it is corrected as follows by Eq. (1).
As a result, the rising shutter speed is increased.         T_Vf= 5 x 3/4 + 2 = 5.75   Thus, by performing the correction as described above, f = 250 mm is the center.
It can be seen that the shutter speed rises from both sides of the focal length and the shutter speed is compressed.   <Determination of program diagram>   Next, a method of determining a program chart for each lens having a different focal length will be described.
.   Rising shutter for each shooting lens (including zoom lens) with different focal length
Speed T_VfAfter the above is obtained as described above, a program chart for each lens must be determined.
And This program diagram is 1 / T_V3Rising right rising from second
(Fig. 4 shows P₁Etc.). But on
The rising shutter speed T obtained in the above embodiment._VfIs a shooting mistake due to camera shake
In order to obtain better photos, it can be said that the shutter speed is assured
The exposure condition of this T_Vf, The aperture value A_VTo a specified amount.
(It is preferable that the shift amount be A_VSWill be shown). Therefore,
In this embodiment, T_VfAperture value A corresponding to_VfIs given E_VA when value is shifted_Vvalue
The program diagram is to be determined. FIG. 3 (A)_VThe value(
Ev_j-E_Vi) Is a diagram provided for explanation of a program diagram when shifting by minutes;
Among them, what is indicated by I (solid line) is the program diagram, and what is indicated by II (broken line)
Is a conventional program diagram. Note that the program diagram as indicated by I is as follows (
According to equations a) and (b), the same E_VT by value_VaAnd T_VbRespectively, and both
T is the larger value of_VIt is obtained by adopting it as a value.       T_Va= E_V・ Y / X + δ (a)       T_Vb= T_Vf, A_V= E_V-T_Vb... (b)   Here, X and Y are constants that define the inclination of the program diagram, and in FIG.
= 8, Y = 3. Δ is E_VT when = 0_VIt is a value, and it is from the following formula (c).
It can be found.     δ = (1-Y / X) · T_Vf-Y (A_Vmin+ A_VS) / X ・ ・ ・ (c)   In this embodiment, means for determining the program diagram indicated by I is provided by the CPU 77.
And the PCU 73. The reason for using PCU73 is that the program diagram
Constants X and Y for determining the slope of the data and constants A for indicating the shift amount_VSIs provided in PCU75 E^TwoIt is stored in the PROM 73a, and the CPU 77 takes in these constants as necessary.
This is because that. X, Y, A_VSIs stored in advance in, for example, the program ROM 77a of the CPU 77.
Of course, a configuration without the PCU 73 may be used. However, as mentioned above, E^TwoPROM
Can easily change these constants even if design changes occur.
Benefits are obtained.   FIGS. 3 (B) to 3 (D) show a CPU for operating a program diagram determining means.
It is a flowchart of FIG. In the calculation for determining the program diagram,
EAH register of RAM77d of CPU77 is T_VEAL register
A_VAcc is T_VfAre used as registers for
. The arithmetic processing and comparison processing performed during the operation are performed by the arithmetic means 77c and the arithmetic means 77c, respectively.
And comparison means 77b.   T_VfLog to register_TwoThe approximate calculation result of f is stored (step 301). next
, T_VfRegister data to T_VIt is stored in a register (step 303). Next, DP
The subject brightness E obtained in U75 (see FIG. 2 (A))_VUsing E_V-T_VPerform the operation of
This result A_VIt is stored in a register (step 305). Then A_VIn the register
The data is the aperture value (A) of the currently used shooting lens._Vmin) And minimum aperture
Value (A_VmaxCheck if the value is within the range between).
_VLeave the data in the register as is,_VminOr A_Vma
x(Steps 307 to 313).
A_VminAnd A_VmaxIs stored in the lens ROM of the taking lens.
These are taken into the CPU from the lens ROM.   Next, the determined A_VT based on the value_VFind a value and use this value as T_VStore in register
(Step 315). Then this T_VThe data in the register is the camera shutter mechanism
It is checked whether the shutter speed is within the ability of the camera._VLes
The register data is kept as is, and if the capacity is out of range, the maximum shutter speed
Degree (shortest exposure time) T_VmaxOr the minimum shutter speed T_VminAny of the following
Replace with any of the values (steps 317 to 323). Step 307-Step
By performing the processing of step 323, it is possible to obtain a diagram indicated by III in FIG. 3 (A).
Can be. T determined as described above_VValue (this value is the value of T in equation (b) above)_Vb Is equivalent to ) Is stored in the A register (step 325).   Next, the CPU 77 executes E^TwoDefine the inclination of the program diagram from PROM73a
Constants X and Y and a constant A indicating the shift amount_VSAre read (step 327). this
X, Y and A_VSAre values according to the design, respectively.
Let X = 8, Y = 3 and A_VSIs 1E_VThe amount corresponds to the minute.   Next, δ is obtained in accordance with the above equation (c), and this δ is stored in the B register (step
329).   Next, according to the above equation (a), T_VaFind a value and use this value as T_VStore in register (
Step 331).   Next, T_VRegister data (T_Va) And A register data (T_Vb) And the ratio
Compare, T_V> A for T_VLeave the register data as is, otherwise
Is T_VThe data of the A register is stored in the register (steps 333, 335). Here
By the processing at, T calculated respectively according to the above-described equations (a) and (b)_VaAnd T_Vbof
The larger value is T_VStored in a register.   The processing shown in steps 337 to 365 after this is the limit maximum shutter of the shutter.
Tta speed T_VmaxAnd the minimum shutter speed T_VminAnd the currently used shooting lens
A_VminAnd A_VmaxT_VValue and A_VIn the process to determine the value
is there.   First, T_VT currently stored in the register_VThe value is the maximum shutter speed of the camera
T_VmaxT if greater than_VSet the register value to T_Vmax(Step 339),
This T_VmaxA using_VA value is obtained (step 341). Next, the obtained A_VIf the value is A_V
> A_VmaxA when_VRegister value is A_VmaxAnd if not,
(Steps 343, 345). A at this time_VThe value is used as the aperture value. Next,
A_VA in register_VT using the value_VA new value is obtained and this T_VValue T_VRegister case
(Step 347). Next, this T_VValue T_VmaxAnd again (step 349
), T for large_VSet the register value to T_VmaxReplace this value with the shutter speed
And T otherwise_VThe value in the register itself is used as the shutter speed. Stay
T at 337_VValue is T_VmaxLess than and this T_VValue and open aperture value A_Vm
inIs the sum of the current subject E_VStep 34 even if the value is exceeded The processing from 1 to step 351 is executed.   On the other hand, at step 337, the current T_VValue is T_VmaxIt is determined that
This T at Step 353_VValue and open aperture value A_VminAnd the sum is E_VIf the value is less than
When set, first, A_VRegister value is A_Vmin(Step 357), and this condition
T under_VA new value is determined and this T_VValue T_VStore in register (step 357)
. Then, this T_VT if the value is less than 0_VReplace the register value with 0 (
Step 361), otherwise, leave as is, T_VThe value in the register is
(The longest exposure time is obtained) T_Vmin(Step 363).
Where T_V<T_VminT for_VminValue is shutter speed, otherwise
Is currently T_VT stored in the register_VThe value is the shutter speed. Also, the aperture is
In either case, it is open.   It should be noted that the present invention is not limited to the above-described embodiment, but will be described below.
Such transformations can be made.   T_VfThe operation of the means for determining the value is limited to the flowcharts shown in FIGS.
It is needless to say that other procedures are not required.   The procedure for determining the program diagram is shown in FIGS. 3 (B) to 3 (D).
The procedure is not limited to the chart, and another procedure may be used.   An apparatus to which the exposure control apparatus of the present invention can be applied is a camera having the structure described in the embodiment.
It is not limited to LA, for example, interchangeable lens type camera equipped only with AE function,
Obviously, the present invention can be applied to a camera having another structure such as an electronic still camera. (The invention's effect)   As is clear from the above description, according to the exposure control device of the present invention, the focus control
Zoom for each taking lens with different distance, or if the taking lens is a zoom lens
Each time the focal length changes due to the camera, proper standing without causing camera shake
Up shutter speed T_VfIs calculated each time, and based on this,
A suitable program diagram is determined.   As a result, not only can an appropriate amount of exposure be obtained, but also the image quality can be improved.
Video can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (A) is a block diagram showing the function of a CPU which is a component of the exposure control device according to the present invention, and FIG. 1 (B) is used to explain the configuration of a RAM. FIG. 1 (C) is a diagram showing an example of use of the accumulator Acc in obtaining T _Vf, and FIGS. 1 (D) to (F) are flowcharts of a CPU for operating means for obtaining T _Vf. 2 (A) to 2 (D) are views for explaining a preferred camera to which the exposure control device of the present invention is applied, and FIG. 3 (A) is a program obtained by the exposure control device of the present invention. FIGS. 3 (B) to 3 (D) show C for operating a means for obtaining a program diagram.
PU Flow Chart FIG. 4 is a diagram showing a program diagram for explaining the conventional and the present invention. 11: photographing lens, 13: movable lens 15: lens system, 17: driving force transmission mechanism 19: lens ROM (Read Only Memory) 21 ... lens side electrical contact group 31: camera body, 33: main mirror 35 ... sub mirror, 37 focus lens 39 pentagonal prism 41 imaging unit 43 movable lens 13 drive mechanism 45, 47 light receiving element 49 central display unit 51 viewfinder display 53 built-in strobe 55 sequence motor 57 ... body side electric contact group 59 ... release switch, 61 ... X contact 71 ... IPU (Indi-cation Processing unit) 73a ... E 2 PROM 73 ... PCU (Power Control unit) 73a ... E 2 PROM 75 ... DPU (Data Processing Unit) 77 ... CPU (Central Processing Unit) 81 ... zoom lens, 83 ... zoom ring 83a ... brush, 83 b ... zoom code plate a ₁ ~a ₄ ... zoom code plate provided with wiring patterns b ₁ ~b ₄ ... brushes contact.

Claims (1)

(1) In order to determine a program chart for exposure control for each photographing lens having a different focal length, the rising shutter speed T _vf of the program chart is set to the focal length f of the photographing lens. Accordingly, in an exposure control apparatus provided with a means for calculating according to the equation T _vf = log ₂ f, the means for calculating T _vf is a lens ROM storing information indicating focal length information of the taking lens, and a CPU. A RAM having an EA register functioning as a 16-bit register, B and C registers each being an 8-bit register, an accumulator, a ROM storing a program for operating a means for obtaining T _vf , a comparing means And a CPU having arithmetic means, the information indicating the focal length of the photographing lens stored in the lens ROM being stored in the EA register. The number of digits of the most significant bit of the focal length information stored in the EA register is determined by the log ₂
An exposure control device, which is means for setting a value of an integer part of f.