JPS62166322A - Exposure control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling exposure of a camera using a lens shutter.

Conventional technology The exposure control method for cameras that use a lens shutter involves measuring external light to determine the opening time of the lens shutter (the time from when the shutter open command is output until when the shutter close command is output). One is the photometry method, and the other is the direct photometry method, which outputs a shutter open command and then outputs a shutter close command when it detects that the amount of light reaching the imaging plane, or the integral value of the equivalent amount of light, has reached a predetermined value. There is.

The former method does not measure the amount of light that actually reaches the imaging plane, resulting in poor exposure control accuracy, so the latter method has recently been adopted.

Problems to be Solved by the Invention However, even with the latter method, due to the inertia of the shutter blades, etc., there is a delay between the output of the shutter closing command and the actual start of the shutter closing, which reduces exposure control accuracy. There is.

Particularly on the high-brightness side where the shutter speed is fast, accuracy deteriorates and there is a strong tendency for overexposure.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that the amount of light that reaches the imaging plane after the shutter opening command is output, or the integral value of the equivalent amount of light, is less than the appropriate exposure amount. The configuration is such that the time required for outputting the shutter closing command after detecting the predetermined value is determined as a function of the time until the predetermined value is reached.

Effect: Therefore, the amount of exposure from when the shutter close command is output to when the shutter is completely closed varies depending on the brightness, but it is a function of the time it takes to reach the predetermined value (a function of brightness), and the amount of exposure after the predetermined value is reached. Since the time until the shutter closing command is output is determined, exposure control accuracy is improved.

Embodiment FIG. 1 is a diagram showing an exposure control method according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part thereof.

In the figure, the image of subject 1 is captured by lens 2.

The reflected light passes through the mirror 3 and forms an image on an imaging section 4 (such as a silver halide film), and a part of the reflected light enters a photometric element 6.

Release pulse 7 from release switch 6 is CPtT8
, the CPU 8 first outputs a reset pulse 9, resets the integral output 11 of the integrating circuit 10 that integrates the output of the photometric element 6, and resets the first timer 12. Next, when a shutter opening command 13 is output to the shutter drive circuit 14, the shutter 3 starts to open. Due to this operation, the light to the photometric element 6 increases as the shutter opening amount 16 changes, so the reset integral output 11 increases as shown. When this output reaches a predetermined value 17 that is smaller than the appropriate exposure amount 16 that is appropriate for the imaging section 4, the comparator 18 outputs a predetermined value detection pulse 19, and measures the elapsed time after outputting the shutter opening command 13. The first timer 12 that is running is stopped. Further, this predetermined value detection pulse 19 is applied to the RQ addressed by the first timer 12.
The variable time setting value 21 from the M table 2o is set in the second timer 22, and the second timer 22 is started. When the time corresponding to the variable time setting value 21 has elapsed since the predetermined value detection pulse 19 was output, the variable time elapsed pulse 23 is output from the second timer 22, so the CPU 8 outputs the shutter closing command 24 and closes the shutter. Close 3. When the shutter 3 closes, the exposure to the imaging section 4 reaches the appropriate exposure amount 16.

In the first embodiment, the reflected light from the imaging section 4 is photometered, but the light in front of the imaging section 4 is separated by a half mirror or the like and is made to enter the photometric element 6. Alternatively, the light that does not pass through the shutter 3 is changed to be equivalent to the light that passes through the photometric element 6.
A similar operation is also possible using a method in which light enters the light source.

Alternatively, a system in which the CPU 8 executes a series of operations from outputting the predetermined value detection pulse 19 to outputting the shutter closing command 24 may be used.

The variable time setting value 21 described above changes to a predetermined value 17 from the time when the shutter opening command 13 is output, as shown in FIG.
The shorter the time until detection, the shorter the time. This is because the higher the brightness is, the more the exposure amount from when the shutter close command 24 is output until the shutter 3 finishes closing has a larger proportion to the appropriate exposure amount 16, so the shutter close command 24 must be output sooner. This is because it will not happen.

Note that the delay time from when the shutter close command 24 is output to when the shutter 3 starts its closing operation becomes longer as the opening amount 16 of the shutter 3 is smaller, so the RQM table 2o
The variable time setting value 21 to be stored in the shutter 3
It is possible to improve accuracy more by changing the opening amount 16 according to the size of the opening amount 16.

Effects of the Invention Therefore, in the exposure control method according to the present invention, the time from when the shutter opening command is output until the amount of light reaching the imaging plane, or the integral value of the equivalent amount of light, reaches a predetermined value less than the appropriate exposure amount. The function determines the time from when the predetermined value is detected until the shutter close command is output.
Exposure control accuracy is improved.

In particular, the effect is noticeable on the high brightness side, where conventional accuracy was poor.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an exposure control method according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part thereof. 3...Shutter, 6...Photometering element, 8
...CPU, 10...Integrator circuit, 11
...Integral output, 12...First timer, 13...Shutter opening command, 16...
...Appropriate exposure amount, 17...Predetermined value, 19...
...Predetermined value detection pulse, 21...Variable time setting value, 23...Variable time elapsed pulse, 24...
... Shutter close command. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] It is a function of the time it takes for the amount of light that reaches the imaging plane after the shutter opening command is output, or the integral value of the equivalent amount of light, to reach a predetermined value less than the appropriate exposure amount, and after the predetermined value is detected. An exposure control method for a camera using a lens shutter, characterized by determining the time until outputting a shutter closing command.