JPH0220841A - Photometry device - Google Patents

Abstract

PURPOSE:To calculate an appropriate exposure value even under high contrast photographing conditions by selecting areas closer to data on the brightness of the central part of a screen and calculating an exposure value based on a value obtained by adding the areas to the central area. CONSTITUTION:When a main object is recognized so as to position it in the center of a photographing screen, a memory means 25 records outputs regarding brightness in each area 40 of the photographing screen subjected to photometry by a photodetector 20. Brightnesses of peripheral areas are subtracted from that of the central part 41, and only area when the value is within a prescribed range is selected. By referring to contents in the memory means 25, brightnesses corresponding to the selected peripheral areas and the central part 41 are read out, and brightness data are averaged to determine an exposure value. In high contrast photographing in which calculation of an exposure value is difficult, an appropriate exposure value is attainable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photometric device for use in cameras such as electronic still cameras, silver halide cameras, and video cameras.

[Conventional technology]

In recent camera photometry devices, for example,
As described in Japanese Patent No. 827, there are known devices that are devised so that proper exposure can be obtained even in backlight photography or stage photography under a spotlight, where it is difficult to calculate the proper exposure. This uses a light-receiving system consisting of a large number of light-receiving elements, and compares the brightness data obtained from each light-receiving element with a dark value, and uses the brightness data that exceeds the dark value as the brightness data when calculating the exposure value. Exclude from Furthermore, when the number of brightness data to be excluded exceeds a predetermined number, the excess brightness data is added to the brightness data used in calculating the exposure value.

[Problem to be solved by the invention]

However, in the photometry method described in the above publication, the darkness value is an average value of a plurality of luminance data, so the darkness value may vary depending on luminance data of objects other than the main subject. Therefore, if this darkness value and the brightness data of the main subject are thick (if they are different, the most important brightness data of the main subject will be excluded from the brightness data when calculating the exposure value, and the main subject will not be accurately reproduced. In addition, in order to position the main subject using pattern recognition, special backlighting (for example, Japanese Patent Publication No. 5B-586
In the case of "Jido Hikari" (as described in Publication No. 08),
The disadvantage is that proper exposure cannot be obtained.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a photometry device that can properly reproduce the main subject even when photographing with high contrast where it is difficult to calculate the exposure value. purpose.

[Means to solve the problem]

In order to achieve the above object, the photometry device of the present invention sets an SM area (spora) in the center of the photographic screen, and
The surrounding photographic screen is divided into a matrix by a plurality of light-receiving elements, and the light is measured for each area. The storage means records these brightness data, and the area selection means subtracts the brightness data of the center from the brightness data of each peripheral area, and selects an area where this value is within a predetermined range. The arithmetic processing means calculates the average brightness data of the selected area plus the center area, and uses this as an exposure value.

[Effect]

According to the above configuration, when the photometry device of the present invention captures the main subject so as to be located at the center of the photographic screen, the H degree output in each area of the photographic screen measured by the light receiving element is recorded by the storage means. Ru. Each TrM3m in the peripheral area
The central value is subtracted from the brightness of each area, and only areas where the value falls within a predetermined range are selected. The brightness corresponding to the selected peripheral area and central area is read out with reference to the storage means, and these brightness data are averaged to determine an exposure value.

Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

In FIG. 1 showing a block diagram of a photometric device of the present invention and an optical system of an electronic still camera 1 incorporating this photometric device, the optical system of the electronic still camera 1 consists of two groups (lens loa,
, 10b) configuration, and an instantaneous diaphragm 11 arranged between the lens 10a and the lens 10b.
．． Beam splitter 12. Quick return movable mirror 13° focusing screen 14. Condenser lens 15. Pentaprism 16. It consists of an eyepiece lens 17 and an imaging lens 18 below the beam brick 12.
A photodiode array 20 for photometry is arranged through the . In addition, a shutter 22 is provided behind the movable mirror 13.
A CCD 21 for imaging is arranged through the .

A signal processing circuit 23 is connected to the photodiode array 20, and a CPU 26 that is operated according to a sequence program written in a program ROM 24 is connected to this signal processing circuit 23. A frame memory 25 is connected to this CPU 26, and a photodiode array 20. Photometric data for each pixel that is serially outputted via the signal processing circuit 23 is stored in address order. The CPU 26 also has a CCD that opens and closes based on the calculation results calculated from the photometric data.
shutter 22. The aperture 11 and release switch 35 are connected.

A signal processing circuit 30 is connected to the CCD 21, and this signal processing circuit 30 writes a video signal to a still video floppy (hereinafter referred to as video floppy) 33 via an FM modulation circuit 31 and a head amplifier 32. It is connected to a magnetic head 34 for use. A motor 36 for rotating the video floppy 33 at a constant speed is arranged below the magnetic head 34, and a driver 37 for driving the motor 36 is connected to the motor 36. Furthermore, a CPU 26 is connected to the driver 37 and head amplifier 32 to drive them.

In addition, a photodiode array 20. A drive circuit 27 and a CCD drive circuit 29 are connected to the CCD 21 to drive these, respectively. C.C.
A synchronizing signal generation circuit 28 is connected to the D drive circuit 29. This synchronization signal generation circuit 28 is also connected to the CPU 26 and the photodiode array 20. CCD
The various pulses necessary to drive the CPU 21 are synchronized with each other, and a master clock pulse for controlling the sequence of the CPU 26 is generated.

Next, the operation of the photometric device of the present invention configured as above will be explained. First, when the video floppy 33 is loaded into the electronic still camera 1 and the power is turned on, the synchronization signal generation circuit 28 causes the CPU 26° drive circuit 27. A master clock pulse is sent to the CCD drive circuit 29, and each drive is started. A signal is sent from the CPU 26 to the driver 37 to drive the motor 36, and the loaded video floppy 33 begins to rotate at approximately 30m5 at 60% per second.
The steady speed of rotation is reached.

When the photographic lens 10 is directed toward a subject, the optical image of the subject captured by the photographic lens 10 is transmitted through the beam splitter 12, reflected by the movable mirror 13, and formed on the focusing screen 14. This formed object image is condensed by a condenser lens 15, and a pentaprism 16. It is observed by the photographer through the eyepiece lens 17. On the other hand, a part of the optical image of the object is guided by the beam splitter 12 to the imaging lens 18 and focused on the photodiode array 20 . The optical image formed on the photodiode array 20 is converted into a luminance signal by the photodiode array 20, subjected to amplification and digitization processing in the signal processing circuit 23, and inputted to the CPU 26. The CPU 26 partially stores this luminance signal in the frame memory 25 according to the program sequence of the program ROM 24.

The photometric area 40 to be photometered by the photodiode array 20 is divided into a matrix shape except for the central spot area 41, as shown in FIG. 2(B).
The brightness of the object observed on the finder screen 42 shown in FIG. 4A is measured for each minute area. The measured brightness data is divided into EV units for each area.
This is shown in the same figure (B). Note that the photometry area 40 displays the entire area of the luminance data stored in the frame memory 25 and corresponds to the exposure frame recorded on the video floppy 33.

The CPU 26 processes the photometric data according to the program sequence shown in FIG. First, from brightness data P(i+(i is 1 to 16) from each minute photometric area in the photometric area 40 divided into a matrix, the spot area 41
"P<=r P(C)" is calculated for each region by subtracting the luminance data P (C) of .

This 'P u> P (C) J becomes a constant value +
(for example, 2EV) and 'P (t>
P (C) J is a constant value kt (for example, -2E
rP m P (
Select an area within the range of c+J and crab+akz. Then, the average brightness data for the entire area including those areas and the spot area 41 is calculated, and this average brightness data is set as the exposure value P.

Expressing this in the formula, becomes.

As the first example of the shooting scene, the second example is the case of front light shooting.
This will be explained with reference to the figures. As shown in Figure (A), the photographer is a person 43 with the sun behind him and mountains and fields in the background.
A commemorative photo will be taken. When the spot area 41 is made to correspond to the face of the person 43, the photometry is P(C)=15EV,
As shown in the same figure (B) in other areas, P (1)
−20, P (2) = 15, ..., P ub
)=10. Therefore, since the area having P(1) and the area having P(+61) are excluded, the exposure value P is =14.2EV, where k+ =2EV and kg=-2EV. Not only 43 but also the surrounding situation is reproduced in a well-balanced manner.

Furthermore, in the case of backlight photography, a photographic scene as shown in FIG. 4(A) is captured in the viewfinder field of view. The brightness data of each area obtained by photometering this photographic screen is shown in the same figure (B
) is recorded in the frame memory 25 as shown in FIG. Therefore, the exposure value P is calculated as follows.

=lIEV As a result, although the scene is normally difficult to determine exposure for, the brightness data of the sun and sky with high brightness are automatically excluded, and the person 45 is faithfully reproduced.

Further, when photographing a subject illuminated by a spotlight as shown in FIG. 5(A), the luminance data recorded in the frame memory 25 becomes as shown in FIG. 5(B). Therefore, the exposure value P is: =17. It is calculated as 3EV. As a result, not only the person 46 but also the situation on the stage illuminated by the spotlight can be reproduced without being overshadowed.

By pressing the release button halfway, etc., the AE black 2 mechanism (
(not shown) to store the exposure value P, decide on the composition while observing the finder image, and press the release button (not shown).

As a result, the release switch 35 is turned ON, and at the same time the movable mirror 13 jumps up, and immediately after this, the exposure value P
The shutter 22 is opened and closed based on.

At the next moment, the movable mirror 13 returns to its original position and the viewfinder field of view is restored, and the optical image, which has been controlled to have an appropriate amount of light, is converted into a video signal by the CCD 21, and then sent to the well-known signal processing circuit 30 and FM modulation circuit B31. The signal is input to the head amplifier 32 via. The head amplifier 32 operates the magnetic head 34 according to instructions from the CPU 26,
The video signal read out from the CCD 21 is instantaneously recorded on a video floppy 33.

Next, a second embodiment of the present invention will be described, which has a different program sequence from the first embodiment described above. Luminance data P for each area, 1. After storing in the frame memory 25, each area is classified according to the following three types of conditions.

(1) P m P (1:) >k+(2)k
g≦P (ri P (C) ≦+C3) P<=
) P<. <k.

Letting the number of regions satisfying these conditions (1), (2), and (3) be nl + n2 + n3, respectively,
When nl is less than or equal to a predetermined number, the exposure value is calculated by averaging the luminance data of an area that is the area that satisfies condition (1) plus the area that satisfies condition (2). Furthermore, when n3 is less than or equal to a predetermined number, the exposure value is calculated by averaging the luminance data of the area that satisfies condition (2) plus the area that satisfies condition (3). Also, r11+rl
When +J is less than or equal to a predetermined number, the exposure value is calculated by averaging the luminance data of the entire area.

〔Effect of the invention〕

As explained above, according to the photometry device of the present invention, areas having brightness data close to the brightness data at the center of the screen are selected, and the brightness data of these areas plus the center area is averaged. Since the exposure value is calculated based on the value obtained from the subject, the brightness may be extremely high compared to the brightness of the subject, not only in the forward direction but also in backlit or spotlight shooting situations, which are high contrast shooting conditions. It is now possible to provide a photometry device that can automatically exclude brightness data in different photometry areas and calculate an appropriate exposure value for a subject.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing the structure of an embodiment of the present invention. FIGS. 2A and 2B are schematic diagrams showing the viewfinder field of view and the brightness data of each photometric area during front-light photography. FIG. 3 is a flowchart showing the main part of the sequence program according to the embodiment of the present invention. FIGS. 4(A) and 4(B) are schematic diagrams showing the viewfinder field of view and brightness data of each photometric area during backlight photography. FIGS. 5A and 5B are schematic diagrams showing the viewfinder field of view and brightness data of each photometric area during spotlight photography. Electronic still camera/photodiode array shutter PU Photometering area Spot area.

Claims (1)

[Claims] (1) In a photometry device that divides a photographic screen into a matrix shape except for the central part, and is equipped with a plurality of light-receiving elements that measure light for each of the central part and each divided area, each of the central part and the peripheral part A storage means for recording the luminance data measured photometrically for each area, and a value obtained by subtracting the brightness data of the central part from the brightness data of each area of the periphery by referring to the brightness data recorded in this storage means. an area selection means for selecting an area where the area is within a predetermined range; and an arithmetic processing means for calculating the average luminance data of the area selected by the area selection means plus the central part, and using this as an exposure value. A photometric device comprising: