JPH01285927A - Exposure controller for camera - Google Patents

Abstract

PURPOSE:To prevent a finished picture from becoming extremely less exposed by substituting an exposure value for a prescribed value if the exposure value of an object with high brightness exceeds the prescribed one when a camera side automatically switches from divided photometery to center-emphasis photometery. CONSTITUTION:The title device is provided with a selecting means 7 capable of selecting a photometeric means 3 in terms of divided photometery and center- emphasis photometery through external selecting operation, a deciding means 8 deciding whether the divided photometery made by the photometeric means 3 can be possible or not based on at least information on a photographing lens. Even if the divided photometery is selected, operation is automatically switched to the center-emphasis photometery according to said information. When the exposure value obtained by calculating through the center-emphasis photometery exceeds the prescribed value, it is substituted for the prescribed value. Thus, the divided photometery and the center-emphasis photometery can be automatically switched, and the current operation is switched to the center-emphasis photometery. Hence, extremely less exposure can be prevented even if a high brightness object is photographed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exposure control device for a camera that can select between split metering and center-weighted metering.

(Prior Art) A conventional exposure control device for a camera measures the light flux incident through the photographic lens, and divides the field (screen) into at least a central part and a peripheral part. The camera's viewfinder is equipped with a metering device capable of center-weighted metering, which measures the center of the subject, and allows the photographer to select between split metering and center-weighted metering by external selection. It is configured.

(Problems to be Solved by the Invention) In the conventional technology as described above, since the photographer can arbitrarily select between split metering and center-weighted metering, for example, when split metering is selected, the shooting lens barrel is When a super-telephoto lens has a large open F value and is dark, the following problems occur. In other words, since it is a dark lens,
Part of the light flux from the subject is not incident on the periphery of the light-receiving surface of the light-receiving element of the photometry means due to the effects of vignetting, etc., making it possible for split photometry to be performed properly or for exposure values resulting from split photometry to be incorrect. There is a problem that it becomes a value.

The present invention was made in view of these problems, and
To provide an exposure control device for a camera that can automatically switch between split metering and center-weighted metering based on lens information of a photographing lens, and can be switched to center-weighted metering and prevents extreme underexposure even when photographing a high-brightness subject. The purpose is to

(Means for solving the problem) In order to solve the above problem, in the present invention, split metering is automatically switched to center-weighted metering, and when the exposure value calculated by the center-weighted metering is equal to or higher than a predetermined value, When the exposure value reaches the predetermined value, the exposure value is replaced with the predetermined value.

(Function) In the present invention, when automatically switching from split metering to center-weighted metering, if the exposure value exceeds a predetermined value even for a high-brightness subject, the exposure value is replaced with the predetermined value. , the exposure will not be extremely underexposed.

(Example) FIGS. 1 to 6 show examples of the present invention. Figure 1 shows a block diagram of the camera, Figure 2 shows a flowchart of the camera's operation, Figure 3 shows changes in exposure value when center-weighted metering is selected, and Figure 4 shows changes from split metering to center-weighted metering. FIG. 5 shows an explanatory diagram of the camera screen, and FIG. 6 shows an explanatory diagram of the divided state of the photometric elements.

In Fig. 1, the exposure control device of the camera consists of a microcomputer (hereinafter referred to as CPU) and this CPU.
It is composed of various circuits, elements, etc., which are controlled by the following.

The switch Swl is turned on in conjunction with half-pressing the release button of the camera, and supplies power to the CPU. Also switch Sw
2 is turned on when the release button is fully pressed, and the CPU
I is activated to 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 CPUI.

The photometric light-receiving element 4 is divided into five parts as shown in FIG. 6, and is arranged, for example, in the finder of a camera to receive the subject light incident through the photographic lens and the finder. The photometric circuit 3 outputs the luminance data for each area of the photometric light-receiving element 4 divided into five areas to the CPUI as photometric information.

The lens information output circuit 5 outputs the aperture f-number (F6), focal length (f), exit pupil path [(Po) or its reciprocal (1/P0) of the photographic lens attached to the camera body to the CPUI as lens information. Output.

The screen information output circuit 6 outputs screen information such as the diffusivity and transmittance of the screen attached to the camera body.
Output to PUI.

A photometry method selection switch 7 is provided on the camera body so as to be operable from the outside, and allows the photographer to arbitrarily select split photometry (here, known multi-pattern photometry) or center-weighted photometry. When this divisional photometry method is selected, the luminance data of the five areas (light-receiving surfaces 4a to 4e in FIG. 6) of the photometry photoreceptor 4 are divided into CPLll and CPLll according to a predetermined algorithm.
The exposure value calculation circuit 9 calculates the exposure value through the exposure value calculation circuit 9.

When the center-weighted metering method is selected, an exposure value is calculated by the exposure value calculation circuit 9 via the CPUI based on the luminance data of the central region of the light receiving element 4 (light receiving surface 4e in FIG. 6).

A multi-pattern photometry determination circuit 8 determines whether multi-pattern photometry is possible based on the aperture F value of the photographing lens output from the lens information output circuit 5. In other words, when the aperture F value is large (and the photographic lens is a dark lens, some of the light flux is vignetted due to the effect of vignetting on the periphery of the light-receiving surface of the light-receiving element 4, and the output from each light-receiving surface 43 to 4e is The brightness data obtained becomes inaccurate, making multi-pattern photometry impossible.On the other hand, multi-pattern photometry is possible when the aperture F-number is small (and the photographing lens is a bright lens).

The photometry method switching circuit 13 selects multi-pattern photometry by the photometry method selection switch 7 and performs photometry when the multi-pattern photometry determination circuit 8 determines that multi-pattern photometry is not possible. , outputs a switching signal for automatically switching from multi-pattern photometry to center-weighted photometry to the CPUI.

When the multi-pattern photometry is switched from multi-pattern photometry to center-weighted photometry by the multi-pattern photometry enable/disable determination circuit 8 and the photometry method switching circuit 13 and the output exceeds a predetermined value, the high-brightness replacement circuit 10 changes the exposure value to the appropriate value as described later. Replace it with a predetermined value and output it to the CPUI. And the shutter control device 11
The aperture control device 12 operates based on the exposure value output from the high brightness replacement circuit 10, and controls the shutter and the aperture.

Next, the operation of the CPUI will be explained based on the flowchart shown in FIG.

When the release button is pressed halfway and the switch SWI is turned on, the CP
Power is supplied to the UI and it starts operating.

In step S1, photometric information is manually input from the photometric circuit 3,
Brightness data of each light receiving surface 4a to 4e of the light receiving element 4 is input.

In step S2, it is determined whether the photographer has selected multi-pattern photometry using the photometry method selection switch 7. If multi-pattern photometry is not selected, proceed to step SIO. In step 310, the high brightness replacement circuit 10
It outputs a command to perform center-weighted photometry, and sends the brightness data of the central light-receiving surface 4e of the light-receiving element 4 to the exposure value calculation circuit 9, which performs calculations to determine the exposure value BV.

Then, if the full-press switch Sw2 is turned on in step S6, the CPUI will set this exposure value BV,
Exposure control is performed based on this and the shooting ends. in this way,
When center-weighted metering is selected by the metering method selection switch 7, as shown in FIG. 3, the exposure value BV calculated by the exposure value calculation circuit 9 and the exposure value BVc (
The CPU controls the shutter control device 11 and the aperture control device 12.
The value used to control the exposure value BV is equal to the value used for controlling the exposure value BV, and the exposure is controlled using the unchanged value of the exposure value BV determined by the exposure value calculation circuit 9. For this reason, in conditions where sunlight is directly incident as shown in Figure 5, there is a risk that mountains, yachts, etc. will be extremely underexposed, but the photographer should choose center-weighted metering himself. Therefore, exposure control is not performed to prevent the main subject (mountain or yacht) from being extremely underexposed by regulating the high brightness side of the exposure value BVc used for control.

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

If the photographing lens is a bright lens in step S3, the process advances to step Sll. In step S11, the five luminance data from the photometry circuit 3 are sent to the exposure value calculation circuit 9, and the exposure value calculation circuit 9 performs exposure calculation by multi-pattern photometry, and in steps S6 and S7, the fully pressed switch Sw2 is When turned on, exposure control is performed and shooting ends.

Furthermore, if the photographing lens is a dark lens in step S3, the process advances to step S4. In step S4, the photometry mode switching circuit 13 operates to automatically switch from multi-pattern photometry to center-weighted photometry, causes the exposure value calculation circuit 9 to perform exposure calculation by center-weighted photometry, and obtains an exposure value BV. Then, the process advances to step S5.

In step S5, an exposure value BVc for exposure control is determined. That is, as shown in FIG. 4, the exposure value BV calculated by the exposure value calculation circuit 9.

, the exposure value BVc used for control is calculated, and here, from the exposure value BVc, which has a one-to-one correspondence with 11'/iBV of the exposure value BV, the exposure value BVc for the exposure control where the high brightness side is regulated is calculated. Exposure value BVc is set.

This is different from the situation where the photographer arbitrarily selects the re-metering method as described above, in which case the photographer automatically switches to center-weighted metering when shooting using multi-pattern metering. The composition is configured so that the resulting photo will not be extremely exposed. For that reason,
If the camera automatically switches from multi-pattern metering to center-weighted metering, the resulting photo will not be accurate even under direct sunlight as shown in Figure 5. In order to prevent extreme underexposure on mountains and yachts, set the high-brightness side (as shown in Figure 4).
n output value BVB≧11'/38V), the exposure value BVc used for control is fixed at II'/3BV.

In steps S6 and S7, based on the exposure (aBVc) set in step S5, the fully pressed switch Sw
2 is turned on, exposure control is performed and photographing is completed.

(Effects of the Invention) As described above, according to the present invention, when the camera side automatically switches from split metering to center-weighted metering, even if the subject is of high brightness, if the exposure value exceeds a predetermined value, the exposure value is Since the value is replaced with the predetermined value, the resulting photograph will not be extremely underexposed, and proper exposure can be obtained with a higher probability.

[Brief explanation of the drawing]

1 to 6 show embodiments of the present invention. Figure 1 shows a professional diagram of the camera, Figure 2 shows a flowchart of the camera's operation, and Figure 3 shows the relationship between exposure value BV and BVc when central point metering is selected. Figure 4 is an explanatory diagram showing the relationship between the exposure value BV and BVC when switching from split metering to center-weighted metering, and Figure 5 is an explanatory diagram showing the relationship between the exposure value BV and BVC when switching from split metering to center-weighted metering. FIG. 6 shows an explanatory diagram of the divided state of the light-receiving element. (Explanation of symbols of main parts) 1...Microcomputer, 5...Lens information output circuit, 7...Photometering method selection switch, 8...Multi-pattern photometry availability determination circuit, 10...
High brightness replacement circuit, 13...Photometry method switching circuit

Claims (2)

[Claims] (1) Split metering, which measures the light flux that enters through the photographic lens and divides the screen (field) into at least the center and the periphery, and center-weighted metering, which measures the center of the screen. a selection means capable of selecting between split photometry and center-weighted photometry of the photometry means by an external selection operation; a determining means for determining whether or not the dividing photometry is selected by the selecting means; and when the determining means determines that the dividing photometry is not possible, automatically switching to the center-weighted metering; a switching means for switching, the switching means switching to the center-weighted photometry;
1. An exposure control device for a camera, comprising: replacement means for replacing the exposure value with the predetermined value when the exposure value calculated by the center-weighted photometry exceeds a predetermined value. (2) The exposure control device for a camera according to claim 1, further comprising prohibition means for prohibiting operation of the replacement means when the center-weighted metering is selected by the selection means.