JPH01288841A - Exposure controller for camera - Google Patents

Abstract

PURPOSE:To execute an exact photometry corresponding to the full-aperture diaphragm diameter of a photographic lens by using a photometric value by a center part photometric or split photometric means, based on a size of the full-aperture diaphragm diameter which has been obtained from lens information related to the full-aperture diaphragm diameter and the limiting full-aperture diaphragm diameter which has been set in advance. CONSTITUTION:When the full-aperture diaphragm diameter of a lens is smaller than the limiting full-aperture diaphragm diameter which has been set in advance, an exposure value determining means 104 determines an exposure value by using a photometric value from a center part photometric means 102, based on information from a lens information means 103. On the other hand, when the full-aperture diaphragm diameter is larger than the limiting full-aperture diaphragm diameter, the exposure value is determined by using a photometric value of a split photometric means 101. According to such a constitution, when a photographer executes an exposure operation by a split photometric system and the photograhic lens whose full-aperture diaphragm diameter is smaller than the limiting full-aperture diaphragm diameter has been installed, an exposure operation by a center part photometric system is executed automatically, therefore, an exact exposure control can be executed.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to an exposure control device for a camera.

B. Prior Art Conventionally, a five-part light receiving element 50 as shown in FIG. 4 has been known as a photometric light receiving element for this type of exposure control device. This divides the field into five areas: one area in the center and four areas in the periphery.

A central light receiving element 51 and peripheral light receiving elements 52 to 55 are arranged corresponding to each area.

On the other hand, FIG. 7 shows a photometric optical system of a TTL camera using the above-mentioned 5-split light receiving element 50. Subject light that enters the camera body through the photographic lens is reflected by a quick return mirror 61 and is directed to a focus plate 62. The image is formed and then the focal plate 6
2, enters the 5-split light receiving element 50 through a condensing lens 64 by a pentaprism 63. In addition, 65 is an eyepiece lens.

66 is a film.

In the conventional exposure control device having the photometric optical system shown in FIG. 7, when split photometry is selected, all outputs of the light receiving elements 51 to 55 are processed by a predetermined algorithm to calculate the exposure value, and central photometry is performed. When is selected, the exposure value is calculated using a center-part photometry method that uses only the output of the center light-receiving element 51, or a center-weighted photometry method that uses the outputs of all light-receiving elements 51 to 55 but weights the photometry value in the center. something is known.

C0 Problems to be Solved by the Invention The dashed-dotted lines in FIG. The photographic lens Q2 is a photographic lens with a small aperture diameter.

Principal light M1. Since Q is incident on the light receiving element 50, the sensitivity distribution on the light receiving element 50 is uniform on both the bottom side and the top side as shown in FIG. However, the chief ray Q2 is
Therefore, the sensitivity distribution on the photodetector 50 is
As shown in the figure, the lower region on the ground side is not photometered, and the ground side cannot be accurately photometered, making it impossible to obtain an appropriate exposure value with the above-mentioned split photometry.

In other words, as mentioned above, for example, in a camera that selects split metering, center-part metering, or center-weighted metering based on the photographer's request, if split metering is selected when a shooting lens with a small aperture diameter is attached, the correct There may be cases where exposure cannot be obtained.

This tendency is particularly strong when a bright reticle with high directivity is used, as has been the case in recent years. Note that in this specification, center-part photometry and center-weighted photometry are collectively referred to as center-part photometry.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure control device for a camera that performs accurate photometry by appropriately selecting split photometry or center photometry in accordance with the open aperture diameter of a photographic lens.

Means for Solving the D0 Problem Explained with reference to FIG. 1, which is a diagram corresponding to the claims, the present invention is a divisional photometry means that receives subject light through a photographic lens and divides both surfaces of the subject into a plurality of areas and measures the light. 101 and
A center photometer 102 that receives subject light through a photographic lens and measures the central part of the photographic scene, and a lens information means 1 that obtains lens information related to the aperture diameter of the photographic lens.
03, and when it is determined from the lens information that the maximum aperture diameter is smaller than the preset maximum maximum aperture diameter, the maximum maximum aperture diameter is determined based on the photometric value from the central photometer 102. The above-mentioned problem is solved by providing an exposure value determining means 104 which determines the exposure value based on the photometric value of the divided photometric means 101 when it is determined that the exposure value is larger than the diameter.

When the maximum aperture diameter is smaller than the preset maximum aperture diameter, the 80 action exposure value determining means 104 uses the center photometry means 10.
The exposure value is determined based on the photometric value from 2, and also using the photometric value of the divided photometry means 101 when the open aperture diameter is larger than the limit open aperture diameter. As a result, for example, when the photographer wishes to perform exposure calculation using the split metering method.

If a photographic lens whose open aperture diameter is smaller than the maximum aperture diameter is attached, exposure calculation is automatically performed using the central metering method, allowing accurate exposure control.

F. Example One embodiment will be described with reference to FIGS. 2 and 3.

FIG. 2 shows the overall configuration of the exposure control device, and shows the photometry circuit 1.
4 performs well-known signal processing such as logarithmic compression on the photometric output of the 5-divided light receiving element 50 shown in FIG. 4 and outputs luminance information for each area. The lens information output circuit 2 outputs lens information corresponding to the open aperture diameter input from the attached photographic lens (not shown). Photometry method selection switch 3
In conjunction with the operation member for selecting the above-mentioned split photometry or center photometry, the photometry method information for identifying them is output. The film sensitivity reading circuit 4 reads, for example, ISO sensitivity information from a film cartridge.

Outputs film sensitivity information. The control circuit 5 includes a CPU,
It includes ROM, RAM, etc., and reads various information from each of the circuits 1 to 4 described above, and inputs brightness information and film sensitivity information corresponding to the selected photometry method to the exposure value calculation circuit 6 according to the processing procedure described later. . The exposure value calculation circuit 6 calculates the exposure value By using a well-known algorithm based on the input luminance information and film sensitivity information, and the control circuit 5
Enter. The control circuit 5 calculates shutter speed and aperture value based on the exposure value By, and the respective control values are input to a shutter control device 7 and an aperture control device 8 to control the shutter and aperture.

Further, the switch SWI is a half-press switch that is turned on when the release button is pressed halfway, and the switch SW2 is a full-press switch that is turned on when the release button is pressed fully.

The operating procedure for exposure control in this embodiment will be explained according to the flowchart in FIG.

This procedure is executed when the half-press switch SWI is turned on, and photometry processing is performed in step S1, and the photometry circuit 1
Then, in step S2, the brightness information of each of the photometric areas 51 to 55 is read.

Based on the signal indicating the photometry method from the selection switch 3, it is determined whether it is split photometry or central photometry, and if it is split photometry, the process proceeds to step S3. It is determined whether the photographic lens thus obtained is a photographic lens capable of divisional photometry. As mentioned above, accurate exposure control is not possible unless the open aperture diameter becomes small and the off-axis light from the subject light does not enter the periphery of the subject, so there is a limit to how much off-axis light can enter the periphery of the subject. When the aperture diameter is determined in advance and a photographic lens with an aperture diameter larger than the maximum aperture diameter is attached, this step S is performed.
3 is affirmed and the process proceeds to step S4.

On the other hand, when a photographic lens having an aperture diameter smaller than the maximum aperture diameter is attached, step S3 is denied and the process proceeds to step S8.

In step S4, the exposure value calculation circuit 6 calculates the exposure value using an algorithm based on the split metering method based on the total brightness information of the light receiving elements 51 to 55 and the film sensitivity.
Calculate exposure value Bv. Next, in step S5, it is determined whether or not the full press switch SW2 is on. If it is affirmative, in step S6, the shutter speed and time determined by the exposure value By are determined via the shutter control device 7 and the aperture control device 8. Photography is performed by controlling the shutter and aperture according to the aperture value. If step S5 is negative, it is determined in step S7 whether the half-press switch SWI is on,
If the answer is negative, the process returns to another procedure, and if the answer is negative, the process returns to step S5.

On the other hand, if step S2 is negative, the selection switch 3
Since the center photometry method has been selected, in step S8, the exposure value calculation circuit 6 calculates the exposure value Bv from the luminance information obtained from the photometry value from the center light receiving element 51 and the film sensitivity. Even if the split metering method is selected and the aperture diameter of the photographing lens is less than the maximum aperture diameter, the process proceeds from step S3 to step S8 and the exposure value By is calculated. When the process advances from step S8 to step S9, it is determined whether or not the fully pressed switch SW2 is on. If the answer is yes, photographing is performed in step S6 in the same manner as described above. If step S9 is denied, step S
At step S10, it is determined whether or not the half-press switch SWI is on. If the answer is negative, the process returns to other procedures, and if the answer is yes, the process returns to step S9.

According to the above procedure, in this embodiment, even if the split metering method is selected with the selection switch 3, if the maximum aperture diameter of the photographing lens is smaller than the predetermined maximum aperture diameter, exposure is performed using the center metering method. An operation is performed.

Although the open aperture diameter itself is used as the lens information, the focal length, exit pupil position, reciprocal of the exit pupil position, etc. corresponding to the open aperture diameter may also be used as the lens information. Further, the present invention is not limited to a single focus photographing lens, but may be a zoom lens, and in the case of a zoom lens, the present invention can be applied to a camera that cannot be replaced. Furthermore, the method of dividing the light-receiving element is not limited to the embodiment, and the number of divisions and the form of division do not matter as long as it is divided into two or more. In addition, in the above description, the light-receiving element for split photometry shown in Fig. 4 is used in both the split photometry method and the center photometry method, but the light-receiving element for center photometry, which is placed separately from the light-receiving element for split photometry, is used. When the center photometry method is selected, exposure calculation may be performed based on the aperture value from the center photometry light receiving element. Furthermore, in the above description, the center photometry method is performed using the center light receiving element 51.
Although the description has been given as a center-part photometry method in which exposure calculations are performed based on photometric values from the center, exposure calculations may also be performed using a center-weighted photometry method.

G0 Effects of the Invention According to the present invention, when the maximum aperture diameter is smaller than the preset limit maximum aperture diameter, based on the photometric value from the central photometer, the maximum aperture diameter is smaller than the maximum maximum aperture diameter. When the value is large, the exposure value is determined using the photometric value of the split metering method, so even if you try to calculate the exposure value using the split metering method, off-axis light from the subject light will enter the peripheral area of the subject. When using a photographic lens with a small maximum aperture diameter,
Exposure calculations are automatically performed using central metering, allowing for accurate exposure control.

[Brief explanation of the drawing]

FIG. 1 is a complaint correspondence diagram. 2 and 3 illustrate one embodiment of the present invention, in which FIG. 2 is a block diagram showing the overall configuration, and FIG. 3 is a flowchart showing an example of a processing procedure for calculating an exposure value. FIG. 4 is a front view of a 5-division photometric light receiving element, FIGS. 5 and 6 are diagrams for explaining the sensitivity distribution of the light receiving element, and FIG. 7 is an optical path diagram of the photometric system. 1: 'fJA optical circuit 2: Lens information output circuit 3: Photometry method selection switch 4: Film sensitivity reading circuit 5: Control circuit 6: Exposure value calculation circuit 7: Shutter control table @ 8: Aperture control device 101: Division photometry means 102: Central photometering means 103: Lens information output circuit 104: Exposure value determining means Patent applicant Fuyuki Nagai Patent attorney Nikon Co., Ltd. Figure 1 Figure 2 Figure S Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1) divisional photometry means that receives subject light through a photographic lens and measures light by dividing the subject screen into a plurality of areas; central photometering means for metering; lens information means for obtaining lens information related to the maximum aperture diameter of the photographing lens; and lens information means for obtaining lens information related to the maximum aperture diameter of the photographing lens; When it is determined that the aperture diameter is larger than the maximum aperture diameter, the exposure value is determined based on the photometry value from the divisional photometry means. 1. An exposure control device for a camera, comprising: exposure value determining means. 2) The divided photometry means is configured with means for respectively measuring the light of a central area of the field screen and a peripheral area located around the central area, and the central part photometry means measures the central area of the divided photometry means. 2. The camera exposure control device according to claim 1, further comprising means for photometering. 3) The exposure control device for a camera according to claim 1, wherein the lens information is information regarding an open aperture diameter of a photographic lens attached to the camera. 4) The exposure control device for a camera according to claim 1, wherein the lens information is information regarding a focal length of a photographic lens attached to the camera. 5) The exposure control device for a camera according to claim 1, wherein the lens information is information regarding the position of an exit pupil of a photographic lens attached to the camera.