JPH0534760A - Exposure correcting method camera - Google Patents

Abstract

PURPOSE:To enhance the accuracy for the correction of exposure corresponding to a T number in an external photometry system automatic exposure camera. CONSTITUTION:The actual value of the T number is obtained by actually measuring the transmissivity of a photographing lens 11 on a stage that the camera is completed. Based on it, the correction value of the T number for correcting the design value of the T number which is previously stored in a microcomputer 4 to the actual value of the T number is obtained. Then, it is written in a non-volatile memory E<2>PROM9. When the exposure is calculated, the camera corrects the design value of the T number by the correction value of the T number and executes the control of the exposure corresponding to the corrected T number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure correction method for an external exposure type automatic exposure camera.

[0002]

2. Description of the Related Art In an external photometric camera, automatic exposure shifts due to the difference between the F number and the T number at the theoretical shutter speed and aperture given to the photometric value. Therefore, in the conventional camera, the T-number design value of the taking lens given by design is stored in the ROM of the microcomputer at the manufacturing stage of the camera, and the camera stores the T-number design value stored in the ROM during the exposure calculation. According to the above, a method of performing exposure compensation has been adopted.

[0003]

However, in the above method, the actual T number of the taking lens and the T stored in advance in the ROM in each finished camera product due to variations in assembling the taking lens, variations in the taking lens itself, and the like. There was a problem that there was an error with the number design value, which hinders automatic exposure.

The present invention has been made based on the above viewpoint, and an object thereof is to provide an exposure correction method for a camera which is effective for accurate exposure correction depending on the T number.

[0005]

According to the present invention, in an external exposure metering type automatic exposure camera which performs exposure correction according to the T number during exposure calculation, the transmittance of the taking lens of the camera is measured at the stage when the camera is completed. Then, the T number actual value is obtained from the measured transmittance, and the T number design value is calculated from the T number actual value and the T number design value stored in advance in the microcomputer of the camera.
The T number correction value for correcting to the actual number number is obtained, and the T number correction value is externally written to the electrically rewritable nonvolatile memory E ² PROM incorporated in the camera through the camera microcomputer, The above-described object is achieved by a camera exposure correction method in which the camera corrects the T number design value with the T number correction value during exposure calculation and performs exposure correction according to the corrected T number.

[0006]

The T-number actual value is calculated from the transmittance of the photographing lens measured at the stage when the camera is completed, and the T-number design value stored in advance in the microcomputer of the camera is used to correct the T-number actual value. The number correction value is obtained, and this is externally written to the E ² PROM of the camera through the camera microcomputer. The camera corrects the T number design value with the T number correction value stored in the E ² PROM during the exposure calculation, and the corrected T number
Adjust the exposure according to the number. As a result, it is possible to perform exposure correction according to the actual T number of the taking lens of each camera, and it is possible to achieve accurate exposure correction according to the T number.

[0007]

1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, reference numeral 1 is an external exposure metering automatic exposure camera, 2 is a T number correction value writing device, and 3 is a transmittance measuring device.

The camera 1 has a microcomputer 4 built-in. The microcomputer 4 controls the distance measuring / photometering unit 5, the shutter control unit 6, the focus adjusting unit 7 and the zoom driving unit 8 and electrically rewrites them. Writing / reading of possible nonvolatile memory E ² PROM 9 is controlled. The distance measuring / photometering unit 5 gives the distance measuring and photometric information to the microcomputer 4, and the shutter control unit 6
Opens and closes the shutter 10, and the focus adjusting unit 7 causes the taking lens 1
1 is moved to the in-focus position and returned to a predetermined position, and the zoom driving unit 8 zooms the lens barrel 12 having the photographing lens 11 therein. Reference numeral 13 denotes a two-stage release switch composed of a first stage SP1 and a second stage SP2, which gives a start signal to the microcomputer 4 when the first stage SP1 is turned on and releases it to the microcomputer 4 when the second stage SP2 is turned on. Give a signal. An encoder 14 gives zoom position information of the lens barrel 12 to the microcomputer 4. A zoom switch 15 gives a zoom operation signal to the microcomputer 4 by its operation. The microcomputer 4 controls the zoom drive unit 8 in response to the operation of the zoom switch 15 to cause the lens barrel 1 to move.
2 is zoom-driven, and in response to the operation of the release switch 13, the distance measuring / photometering unit 5, the focus adjusting unit 7, and the shutter control unit 6 are controlled to perform shooting with automatic focus and automatic exposure. ..

The T number design value given by design is stored in the ROM of the microcomputer 4. In this example, the T-number design value stored in the ROM is 10
These ten T-number design values T _{S1 to} T _S10 are 10 point zoom positions P _{1 to} P ₁₀ from standard to telephoto.
It corresponds to. The T number design values T _{S1 to} T _S10 are T numbers at each zoom position given at the design stage of the camera, and as described above, due to variations in assembling the taking lens 11 and variations in the taking lens 11 itself, etc. An error will occur with respect to the actual T number of each individual camera finished product, that is, the actual value of the T number. E ² PRO
The M9, ten T number correction value A ₁ to A ₁₀ for correcting the T number design value T _S1 through T _{S1 0} to T number actual values for the individual camera finished products, at the stage where the camera is completed , Is written based on the actual measurement of the transmittance of the taking lens 11 of each camera. Ten T-number correction values A _{1 to} A
₁₀ corresponds to T number design values T _{S1 to} T _S10 . The microcomputer 4 sets the T number correction values A _{1 to} A ₁₀ from the E ² PROM 9 to the RAM of the microcomputer 4 at the time of power-on reset, and sets the zoom position information from the encoder 14 at the time of exposure calculation according to the flowchart of FIG. Based on the T-number design value and T-number correction value corresponding to the current zoom position,
The number design value is corrected with the T number correction value, and the exposure is corrected according to the corrected T number.

The T number correction value writing device 2 is, for example, a general-purpose computer, and is connected to the microcomputer 4 via the terminal 16 of the camera 1 when the camera 1 is completed. The transmittance measuring device 3 has a transmittance calculating unit 17, a light source unit 18, and a light receiving unit 19, and when the camera is completed, the light source unit 18 and the light receiving unit 19 sandwich the taking lens 11 of the camera 1 to The taking lens 1 of the camera 1 is arranged on the optical axis and under the control of the T number correction value writing device 2.
The transmittance of 1 is measured, and the measured transmittance is given to the T number correction value writing device 2. T number correction value writing device 2
According to the flowchart of FIG. 2, each zoom position P ₁
Calculating a T number correction value A ₁ to A ₁₀ in to P _10,
These are written in the E ² PROM 9 of the camera 1.

FIG. 2 is a flow chart showing the writing of the T number correction values A _{1 to} A _{10 to} the E ² PROM 9 by the T number correction value writing device 2.

The T number correction value writing device 2 and the transmittance measuring device 3 are set in the completed camera 1 as described above, and the program of the T number correction value writing device 2 is started. The T number correction value writing device 2 first instructs the microcomputer 4 of the camera 1 to open the shutter 10 in step 20, opens the shutter 10, and then enters step 21 to correct the T number at the zoom position P _1. The writing process of the value A ₁ is started. In the writing process of the T number correction value A ₁ in step 21, first, the microcomputer 4 of the camera ₁ is instructed to the zoom position P ₁ , the lens barrel 12 is set to the zoom position P ₁ , and then the transmittance measuring device 3 is set. Is measured to measure the transmittance of the photographing lens 11 at the zoom position P _1, and the measured transmittance is taken. Next, the T number actual value at the zoom position P ₁ is obtained from the taken-in transmittance, and T for correcting the T number design value T _S1 to this T number actual value.
After determining the number correction value A _1, the microcomputer 4 of the camera 1 of the T-number correction value A ₁ E ² PROM9
It gives a write instruction to the T number correction value A ₁ to E ² PROM9 through the microcomputer 4 write and terminates the writing process of the T-number correction value A ₁ of the zoom position P _1. Then, the T number correction values A _{2 to} A _{10 at} the zoom positions P _{2 to} P ₁₀ are sequentially written into the E ² PROM 9 in the same manner as described above, and the T number correction values A ₁ to
When the writing of A _{10 to} the E ² PROM 9 is completed, step 22 is performed.
to go into. In step 22, the microcomputer 4 of the camera 1 is instructed to release the shutter 10 and the shutter 1 is released.
0 is closed to complete the writing of the T number correction values A _{1 to} A ₁₀ . At the end of writing the T number correction values A _{1 to} A ₁₀ , the camera 1 is removed from the T number correction value writing device 2 and the transmittance measuring device 3.

FIG. 3 shows the microcomputer 4 of the camera 1.
3 is a flowchart of exposure control by the.

When the first stage SP1 of the release switch 13 is turned on, the microcomputer 4 enters the distance measurement / photometry processing in step 30 and obtains the distance measurement / photometry information from the distance measurement / photometry unit 5. Then, the next step 31 is entered. In step 31, zoom position information is fetched from the encoder 14, and in the next step 32, the T number design value and T number correction value corresponding to the current zoom position are read out, and then in step 33, the T number design value is changed to the T number correction value. Correct with. Next, in step 34, after exposure calculation including exposure correction according to the corrected T number is performed, step 35 is entered. In step 35, it is determined whether or not the second stage SP2 of the release switch 13 has been turned on. If it has not been turned on, step 36 is entered, and if it is turned on, step 37 is entered. At step 36, ON / OFF determination of the first stage SP1 of the release switch 13 is performed. If the first stage SP1 remains on, the process returns to step 35, and if it is off, the standby state is entered. In step 37, the exposure processing is performed by controlling the focus adjustment section 7 and the shutter control section 6 according to the distance measurement information in step 30 and the exposure calculation result in step 34.

In the embodiment described above, the T number correction value for correcting the T number design value to the T number actual value is written in the E ² PROM at the stage when the camera is completed, and the T number correction is performed during the exposure calculation. The T number design value was corrected by the value, and the exposure was corrected according to the corrected T number. However, the actual T number at the stage when the camera was completed is written to the E ² PROM, and the T number is calculated when the exposure is calculated. It is also possible to perform exposure correction according to the actual value.

[0017]

As described above, according to the present invention, the T number actual value is obtained from the transmittance of the photographing lens measured at the stage when the camera is completed, and the T number design prestored in the microcomputer of the camera is obtained. Obtain the T number correction value to correct the value to the above T number actual value,
This is externally written into the camera's E ² PROM via the camera's microcomputer, and the camera corrects the T number design value with the T number correction value stored in the E ² PROM at the time of exposure calculation, and corrects it. Since the exposure compensation is performed according to the T number, the exposure compensation can be performed according to the actual T number of the photographing lens of each camera, and the exposure compensation according to the T number can be made accurate. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing writing of a T number correction value to an E ² PROM by a T number correction value writing device.

FIG. 3 is a flowchart of exposure control by the microcomputer of the camera.

[Explanation of symbols]

1 Camera 2 T Number Correction Value Writing Device 3 Transmittance Measuring Device 4 Microcomputer 9 E ² PROM

Claims (1)

Claim: What is claimed is: 1. In an external exposure metering automatic exposure camera that performs exposure compensation according to the T number during exposure calculation, the transmittance of the taking lens of the camera is measured and measured at the stage when the camera is completed. The T number actual value is obtained from the transmittance, and T for correcting the T number actual value to the T number actual value from the T number actual value and the T number actual value stored in advance in the microcomputer of the camera.
A number correction value is obtained, and the T number correction value is written into an electrically rewritable non-volatile memory E ² PROM built in the camera from the outside through a microcomputer of the camera. The corrected T value is obtained by correcting the T number design value with the number correction value.
An exposure compensation method for cameras that compensates exposure according to the number.