JP2535798B2 - Camera exposure controller - Google Patents

Description

The present invention relates to an exposure control device for a camera.

(Prior Art) An exposure control device for a conventional camera measures a luminous flux incident through a taking lens and divides the field (screen) into at least a central portion and a peripheral portion to perform photometry. The viewfinder of the camera is equipped with a metering means capable of center-weighted metering that measures the center of the field so that divided metering and center-weighted metering can be selected by the photographer's external selection operation. It is configured.

(Problems to be Solved by the Invention) In the conventional technique as described above, since the photographer can arbitrarily select the divided metering and the center-weighted metering, for example, when the divided metering is selected, the taking lens barrel is If the lens is a super-telephoto lens and has a large open F value and is dark, the following problems occur. That is, since it is a dark lens, a part of the light flux from the object field does not enter the peripheral portion of the light receiving surface of the light receiving element of the photometric means due to the effect of vignetting, etc. There is a problem that the exposure value obtained by photometry becomes an inappropriate value.

The present invention has been made in view of such a problem, and an object thereof is to provide an exposure control device for a camera that can obtain an appropriate exposure value for any shooting lens based on the lens information of the shooting lens.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, the luminous flux incident through the taking lens is measured to measure the area including the peripheral portion of the screen (field of view). A first light metering means and a second light metering means for performing a second light metering for measuring a central area not including the peripheral portion of the screen, and a light metering means for selecting the first light meter and the second light meter. Selecting means, calculating means for calculating an exposure value based on the output from the photometry means, and the second photometry according to the lens information of the taking lens when the first photometry is selected by the selection means And a replacing means for replacing the exposure value with the predetermined value when the exposure value calculated based on the second photometry becomes a predetermined value or more. .

(Operation) In the present invention, when the first photometry for measuring the area including the peripheral portion is switched to the second photometry for measuring the area not including the peripheral portion, the exposure value is predetermined even if the subject has high brightness. When it exceeds the value, the exposure value is replaced with the specified value,
The exposure is never underexposed.

(Embodiment) FIGS. 1 to 6 show an embodiment of the present invention. FIG. 1 shows a block diagram of the camera, FIG. 2 shows a flow chart of the operation of the camera, FIG. 3 shows changes in the exposure value when center-weighted metering is selected, and FIG. Fig. 5 shows changes in the exposure value due to center-weighted metering when switching to weighted metering, and Fig. 5 shows an explanatory diagram of the screen of the camera.
The figure shows an explanatory view of a divided state of the photometric element.

In FIG. 1, an exposure control device of a camera is composed of a microcomputer (hereinafter referred to as CPU) 1 and each circuit, element, etc. described below which is controlled by the CPU 1.

The switch Sw1 is turned on in synchronization with the half-press of the release button of the camera to supply power to the CPU1. The switch Sw2 is
It is turned on in conjunction with the full press of the release button to operate the CPU1 and perform exposure control.

The film sensitivity reading circuit 2 reads the film sensitivity of the film loaded in the camera body and outputs the film sensitivity information to the CPU 1.

The photometric light receiving element 4 is divided into five as shown in FIG. 6, is arranged in, for example, the viewfinder of the camera, and receives the subject light incident through the taking lens and the viewfinder. The photometric circuit 3 outputs the brightness data for each area of the photometric light receiving element 4 divided into 5 to the CPU 1 as photometric information.

The lens information output circuit 5 uses, as lens information, the open F value (F ₀ ), focal length (f), exit pupil distance (P ₀ ) or reciprocal number (1 / P ₀ ) of the taking lens mounted on the camera body.
Output to CPU1.

The screen information output circuit 6 outputs screen information such as diffusivity and transmittance of the screen mounted on the camera body.
Output to CPU1.

The photometric method selection switch 7 is provided on the camera body so that it can be operated externally, and the photographer can perform divided photometry (here,
Known multi-pattern photometry) or center-weighted photometry can be selected. When this split photometric method is selected, the brightness data of the five areas (light receiving surfaces 4a to 4e in FIG. 6) of the photometric light receiving element 4 are calculated by the exposure value calculation circuit 9 via the CPU 1 according to a predetermined algorithm. Get the exposure value. When the center-weighted photometry method is selected, the exposure value is calculated by the exposure value calculation circuit 9 via the CPU 1 based on the brightness data of the central region of the light receiving element 4 (light receiving surface 4e in FIG. 6).

The multi-pattern photometry availability determination circuit 8 determines whether multi-pattern photometry is possible based on the open F value of the taking lens output from the lens information output circuit 5. That is, when the open F value is large and the taking lens is a dark lens, a part of the light flux is vignetting due to the effect of vignetting on the peripheral part of the light receiving surface of the light receiving element 4, and the brightness output from each of the light receiving surfaces 4a to 4e. The data becomes inaccurate and multi-pattern photometry becomes impossible. On the contrary, multi-pattern photometry is possible when the open F value is small and the taking lens is a bright lens.

When the multi-pattern photometry is selected by the photometry system selection switch 7 and the multi-pattern photometry availability determination circuit 8 determines that the multi-pattern photometry is impossible, the photometry system switching circuit 13 , Outputs a switching signal to CPU1 to automatically switch from multi-pattern photometry to center-weighted photometry.

The high-intensity replacement circuit 10 switches from multi-pattern photometry to center-weighted photometry by the multi-pattern photometry availability determination circuit 8 and photometry method switching circuit 13, and the exposure value calculated by the exposure calculation circuit 9 exceeds the predetermined value and is output. If so, the exposure value is replaced with the predetermined value and output to the CPU 1 as described later. Then, the shutter control device 11 and the aperture control device 12 operate based on the exposure value output from the high brightness replacement circuit 10 to control the shutter and aperture.

Next, the operation of the CPU 1 will be described with reference to the flowchart of FIG.

When the release button half-press switch Sw1 is turned on, the CPU1
Power is supplied to and starts operating.

In step S1, input photometric information from the photometric circuit 3,
The brightness data of each of the light receiving surfaces 4a to 4e of the light receiving element 4 is input.

In step S2, it is determined whether or not the photographer has selected the multi-pattern photometry with the photometry method selection switch 7. If multi-pattern photometry is not selected, the process proceeds to step S10, in which the operation of the high-intensity replacement circuit 10 is prohibited and a command for center-weighted photometry is output, and the exposure value calculation circuit 9 outputs the light-receiving element 4 The brightness data of the central light-receiving surface 4e is sent and calculation is performed to obtain the exposure value BV _a . If the full-press switch Sw2 is turned on in step S6, step S6
At 7, the CPU 1 controls the exposure based on this exposure value BV _a and ends the shooting. In this way, when the center-weighted photometry is selected by the photometry method selection switch 7, as shown in FIG.
The exposure value BV _a obtained by the exposure value calculation circuit 9 is equal to the exposure value BV _c (value when the CPU 1 controls the shutter control device 11 and the aperture control device 12) used for control, and the exposure value calculation circuit 9 The exposure is controlled by the obtained exposure value BV _a as it is. Therefore, when sunlight is directly incident as shown in FIG. 5, mountains and yachts may be extremely underexposed, but the photographer chooses center-weighted photometry by himself. Therefore, the high-brightness side of the exposure value BV _c used for control is not regulated to prevent the main subject (mountain or yacht) from being extremely underexposed.

If multi-pattern photometry is selected in step S2, the process proceeds to step S3. In step S3, it is determined based on the lens information input from the lens information output circuit 5 in step S9 whether multi-pattern photometry is possible.

If the taking lens is a bright lens in step S3, the process proceeds to step S11. In step S11, photometric circuit 3
The five brightness data from are sent to the exposure value calculation circuit 9, and the exposure value calculation circuit 9 performs the exposure calculation by the multi-pattern photometry. At step S6 and step S7, the exposure control is performed with the full-press switch Sw2 being turned on. Stop shooting.

If the taking lens is a dark lens in step S3, the process proceeds to step S4. In step S4, the photometry method switching circuit 13 operates to automatically switch from multi-pattern photometry to center-weighted photometry, and the exposure value calculation circuit 9 is caused to perform exposure calculation by center-weighted photometry to obtain the exposure value BV _a . Then, the process proceeds to step S5.

In step S5, an exposure value BV _c for exposure control is _calculated . That is, as shown in FIG. 4, the exposure value calculation circuit 9
The exposure value BV _c used for the control is calculated with respect to the exposure value BV _a calculated by the following, and here, from the exposure value BV _c corresponding to 1: 1 with 11 1/3 BV of the exposure value BV _a as a boundary, The exposure value BV _c is set for the exposure control where the high brightness side is restricted.

This is different from the situation where the photographer arbitrarily selected both metering methods as described above, and the camera automatically switches to center-weighted metering when the photographer is shooting as if performing multi-pattern metering. When the photo is taken, the resulting photo is constructed so that it will not be extremely exposed. Therefore, when multi-pattern photometry is automatically switched to center-weighted photometry on the camera side, even if the sunlight is directly incident as shown in FIG. The exposure value BV used for control on the high brightness side (exposure value BV _a ≧ 11 1/3 BV) as shown in Fig. 4 in order to prevent the photograph being taken from being extremely underexposed on mountains or yachts.
_c is fixed at 11 1/3 BV.

In step S6 and step S7, based on the exposure value BV _c set in the step S5, and ends the shooting performed exposure control with the ON of the full press switch Sw2.

As described above, according to the present embodiment, when the camera automatically switches from the divided photometry to the center-weighted photometry, even if the subject has high brightness, the exposure value is set to the predetermined value when the exposure value exceeds the predetermined value. Since the value is replaced with a value, it is possible to obtain a proper exposure with a higher probability, without the resulting photograph being extremely underexposed.

(Effect of the Invention) As described above, according to the present invention, in the case where the first photometry for performing photometry on the area including the peripheral portion of the screen is selected, the area not including the peripheral portion is selected according to the lens information of the photographing lens. Since the mode is switched to the second photometry in which the photometry is performed, it is possible to prevent the influence on the photometry due to vignetting on the peripheral portion of the screen that occurs when a shooting lens having a large open F value is attached.

In addition, when the exposure value calculated based on the second photometry becomes a predetermined value or more, the exposure value is replaced with the predetermined value,
For example, even if there is a high-brightness subject in a part of the shooting screen, the exposure will not be extremely underexposed, and the exposure value will deviate significantly from the exposure value intended by the photographer who selects the first metering including the peripheral portion of the screen. There is no end.

[Brief description of drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 shows a block diagram of the camera, FIG. 2 shows a flowchart of the operation of the camera, and FIG. 3 is an explanatory diagram showing the relationship between the exposure values BV _a and BV _c when center-weighted photometry is selected. Fig. 4 is an explanatory diagram showing the relationship between the exposure values BV _a and BV _c by center-weighted metering when switching from split metering to center-weighted metering, and Fig. 5 is the screen of the camera (light-receiving element surface). ), And FIG. 6 is an explanatory view of a divided state of the light receiving element. (Description of symbols of main parts) 1 ... Microcomputer, 5 ... Lens information output circuit, 7 ... Metering method selection switch, 8 ... Multi-pattern photometric availability determination circuit, 10 ... High brightness replacement circuit, 13 ... ... Photometric method switching circuit

Claims (3)

(57) [Claims] 1. A first photometry for measuring a light beam incident through a taking lens to measure a region including a peripheral portion of a screen (field) and a central region of the screen not including the peripheral portion. A photometric unit for performing a second photometric process for performing photometry, a selection unit for selecting the first photometric unit and the second photometric unit of the photometric unit, and an exposure value calculated based on an output from the photometric unit. And a switching means for switching to the second photometry according to the lens information of the photographing lens when the first photometry is selected by the selection means, and an exposure calculated based on the second photometry. An exposure calculation device for a camera, comprising: a replacement unit that replaces the exposure value with the predetermined value when the value exceeds a predetermined value. 2. The first photometry is a split photometry in which the screen is divided into a central portion and a peripheral portion, and the second photometry is a central portion in which the central portion of the screen is intensively measured. The exposure control device for a camera according to claim 1, wherein the exposure metering is important. 3. The exposure control device for a camera according to claim 1, further comprising a prohibiting unit that prohibits the operation of the replacing unit when the second photometry is selected by the selecting unit.