JPS62203142A - Exposure determining device for camera - Google Patents

Abstract

PURPOSE:To perform more proper exposure without any deterioration in operativity by providing an exposure control means which obtains an exposure value on the basis of the largest and the smallest light measurement outputs among all light measurement areas of a light measuring means and respective outputs from a center light measurement area and adjacent light measurement areas. CONSTITUTION:The size of a subject is found from information on the distance to the subject and focal length information on a photographic lens to estimate which light measurement area the size corresponds to. When it is judged that the size corresponds to the light measurement area of a silicon photodiode SPD1, the gradient quantity of the brightness of a center part obtained from the light measurement output of the SPD1 and the light measurement outputs of silicon photodiodes SPD2 and SPD3, i.e. the brightness relation between the main subject and its background is found. Then, the current exposure value is determined according to the brightness relation on the basis of the largest and smallest values among outputs of silicon photodiodes SPD1-SPD7 and the light measured value of the center part. Consequently, photography with proper exposure is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an exposure determining device for a camera that divides a field, measures light, and determines exposure so that the main subject is properly exposed.

(Background of the Invention) Methods for determining exposure when taking a photograph can be broadly classified into an incident light method and a reflected light method. The incident light type requires photometry near the main subject, and is extremely inconvenient for general photography. On the other hand, since the reflected light type is the simplest photometry method, all exposure determining devices built into cameras are of this type. Using a reflected light type exposure meter on a camera has the advantage of being easy to measure, but on the other hand, it is affected by the reflectance of the subject, and it is unclear which part of the subject and in what range it should be measured. There are essential problems such as the fact that

However, a reflected light type exposure determining device is indispensable for determining the exposure of a camera, and if the camera could be equipped with a device that compensates for the above problems, it would be possible to achieve more appropriate exposure. This makes it possible to easily and automatically take close photos, and in view of this, various types of cameras have been proposed. For example, a method that automatically determines exposure based on the output from each point by performing a pre-metering operation in which a metering point provided in the center of the shooting screen is adjusted to each point on the shooting screen (
A method (multi-spot metering) or a method (multi-spot metering) that measures light by dividing the shooting screen into several areas and automatically determines exposure based on information such as the magnitude or difference in brightness between the areas. evaluative photometry method). However, the former type is one of the best if used by someone who has enough time to decide on the exposure and who fully understands the concept of exposure, including the reflectance of the subject. However, it is difficult for the average person to use it, and I don't think anyone can use it easily.In addition, in the latter type, the way to use the camera is exactly the same as before; It can be said to be very good because it allows you to obtain better photos, but the amount of exposure compensation is modest because the algorithm does not determine the exposure value based on the focal length of the lens used and the distance to the main subject. It was set to .

As mentioned above, with conventional devices, it was not possible to effectively and reliably know how much brighter or darker the main subject, which would be placed in the center of the shooting screen, was than the background, so it was difficult to know in backlit scenes etc. I couldn't simply give the right exposure.

(Object of the Invention) An object of the present invention is to provide an exposure determining device for a camera that can solve the above-mentioned problems and provide a more appropriate exposure without deteriorating the operability.

(Features of the Invention) In order to achieve the above object, the present invention provides that when it is determined that the size of the main subject image corresponds to the central photometric area based on the distance information to the main subject and the focal length information of the photographing lens, , depending on the relationship between the brightness of the main subject and the background obtained by each output from the center all light area and the adjacent photometry area, the maximum or minimum photometry output of all the photometry areas of the photometry means and the center photometry area and , an exposure control means is provided that determines the exposure value based on each output from the adjacent photometry area, and the exposure is determined using an exposure calculation formula equivalent to performing exposure compensation after knowing the size of the main subject image. The feature is that the value is determined.

(Embodiments of the Invention) The present invention will be described below in detail based on illustrated embodiments.

FIG. 1.2 is a diagram showing an embodiment of the present invention. 5PD
I~5PD7 are silicon photodiodes constituting a light receiving sensor that measures field brightness in a division pattern corresponding to the photographic screen 1 as shown in FIG. 2, 2~8 are logarithmic compression diodes, 9~15 are operational amplifiers, 16 to 22 are analog switches that are turned on and off according to signals from a decoder, which will be described later; 23 is an operational amplifier; 24 is a diode; and a constant current source 2 that flows a forward current Iref through the diode 24.
5 constitutes a circuit that compensates for the reverse saturation current of the logarithmic compression diodes 2 to 8. 26 is operational amplifier 27
．． A resistor having a temperature coefficient that performs temperature compensation for the logarithmic compression diodes 2 to 8 and the diode 24 together with the resistor 28; 29; and 30 a resistor fixed to the photographing lens barrel;
1 is the resistor 2 which is connected to the rotation of the distance ring of the photographing lens.
A voltage (voltage obtained by dividing the reference voltage Vref) corresponding to the focus position of the photographing lens is generated in the slider 31 that slides on the slider 9 . 32 is a slider that slides on the resistor 30 in conjunction with the rotation of the zoom ring of the photographing lens;
A voltage (a voltage obtained by dividing the reference voltage Vref) corresponding to the zoom position (focal length) at that time is generated in the slider 32.

33 is an arithmetic control circuit equipped with an arithmetic function and various control functions;
34 to 36 are analog switches that are turned on and off according to signals from the arithmetic control circuit 33; 37 is an A/D conversion circuit that converts analog signals inputted through the analog switches 34 to 36 into digital signals; and 38 is the arithmetic control circuit. Analog switch 16 according to the signal from circuit 33
A decoder 39 selects (turns on) 22, a distance detecting section including an infrared light emitting diode, a light receiving element for receiving the reflected infrared light from the subject, and the distance detected by the distance detecting section. A, which is equipped with a drive control unit that drives the photographing lens to the in-focus position by a motor 40 based on a distance signal.
The F control circuit 41 is a switch that is turned on at the first stroke of the release button.

Next, the operation according to the flowcharts of FIGS. 3 to 5 will be explained. When the first stroke of the release button is performed and the switch 41 is turned on, the arithmetic control circuit 33 turns on the analog switch 35 and outputs an operation start signal to the AF control circuit 39. Then, the distance detection section in the AF control circuit 39 starts an operation to obtain a distance signal to the main subject located at the center of the photographic screen. On the other hand, a voltage is generated in the slider 31 according to the rotational position of the distance ring of the photographing lens, and this signal is sent to the A/D via the analog switch 35.
The signal is input to the conversion circuit 37, converted into a digital signal, and then input to the drive control section of the AF control circuit 39 via the arithmetic control circuit 33. When the distance signal and distance ring position signal are input, the drive control section in the AF control circuit 39 determines whether AF is successful or not based on these information, and if it is determined to be successful, drives the motor 40. control, i.e. motor 40
The rotation direction and speed of the lens are controlled to move the photographic lens to the in-focus position, and if the photographic lens is not successful, the photographic lens is moved to the infinite position. By the way, when it is not a success,
Although it differs depending on the AF method, this may occur when the contrast of the subject is low or when the subject is located far away. Thereafter, when it is determined that the photographing lens has completed focusing or moving to the infinite position, the AF control circuit 39 stops the motor 40 and outputs an AF end signal to the arithmetic control circuit 33.

When the AF end signal is input, the arithmetic control circuit 33 stores the position signal where the photographic lens (range ring) is stopped, turns off the analog switch 35, and turns on the analog switch 36. analog switch 3
6 is turned on, a voltage corresponding to the rotational position of the zoom ring generated in the slider 32 is transferred to A via the switch.
The signal is input to the /D conversion circuit 37, converted into a digital signal, and then input to the arithmetic control circuit 33, where the signal is stored together with the position signal of the photographing lens. As a result, distance information corresponding to the distance from the main subject to the camera and focal length information f of the photographic lens are stored in the arithmetic control circuit 33, and based on these information, the arithmetic control circuit 33 stores the distance information corresponding to the distance from the main subject to the camera. The magnification α is calculated from the formula α=f/D. Further, the analog switch 36 is turned off and the analog switch 34 is turned on, and the analog switches 16 to 22 are sequentially turned on via the decoder 38, and the photometric signals of the silicon phototransistors 5PDI to 5PD7 output from the operational amplifiers 9 to 15 are outputted from the operational amplifiers 9 to 15. The operational amplifier 23, 2
7. The analog switch 34 and the A/D conversion circuit 3
7, etc., and the corresponding brightness values B V
Find I” B V 7.

Next, the arithmetic control circuit 33 calculates a center-weighted average photometric value B V m e and two types of center-part partial photometric values BVc, BVc2 from the brightness values Bvl to BV using the following equations.

BVme= (2BV, +E3v2+BV3 +BV4
+BV5+BV6+BV7)/8 BVC+ = (3BVt +2BV2 +BV3)
/6BVc2 = (2BV, +BV1)73 Next, the exposure correction J% ADJ is determined from the following relationship between the central brightness values BV and -BV3). Note that N (=0
．． 25) is a threshold value when determining the exposure correction amount ADJ.

1) BY, -BV2 >N, and BVz -BV3>N
In other words, when it is determined that the main subject is much brighter than the background, the exposure correction m A DJ is set to "-2".

2) When it is determined that the relationship of BV2-BV,>N and BV3-BV2>N, that is, the main subject is considerably darker than the background, the exposure correction amount ADJ is set to "+2".

3) BVI BV2 >N, and -'') BV, -BV3
>N, that is, when it is determined that the main subject is a little brighter than the background, the exposure correction amount ADJ is set to "-1".

4) When the relationship of BV, -BV3>N and BV2-BV3>N is satisfied, that is, when it is determined that the main subject is a little brighter than the background, similarly to 3) above, the exposure correction amount ADJ is set to "-1".

5) When it is determined that BV2-BVI >N and BV3-BV, >N, that is, the main subject is a little darker than the background, the exposure correction amount ADJ is set to "+1".

6) The relationship between BV3-BV,>N and BV3-BV2>N, that is, if it is determined that the main subject is a little brighter than the background as in 5) above, the exposure correction amount ADJ is set to "+1".

7) In cases other than the above, it is determined that there is almost no difference in brightness between the main subject and the background, and the exposure correction amount ADJ is set to "0".

Furthermore, the center-weighted average photometric value B V m e is greater than a certain minimum brightness value BVst required for daytime strobe synchronization, and the distance information to the main subject is greater than the maximum distance information Dst that the strobe light can reach. When the value of the exposure correction 1ADJ is "+2" (in the case of strong backlight), a warning signal is issued indicating that it is better to perform strobe daytime synchronization.

Next, the arithmetic control circuit 33 calculates the ratio of the main subject image to the photographic screen 1 according to the subject magnification α determined by the formula α=f/D, that is, the size to which the main subject image corresponds to which photometric area. The central part photometric value B
Vc1. BVc2 Center-weighted average photometric value BVme or photometric value BVa calculated based on the exposure correction amount ADJ
Select one of the I-BVaa and enter the information BV
From the film sensitivity (SV) and the exposure program diagram, the values of the aperture value AV and the shutter speed TV are determined, that is, the exposure information is determined. In other words, 1) When α>0.06, the main subject image has a fairly large proportion to the photographic screen 1 (assuming the main subject is a human face, for example, the proportion corresponding to the photometric area of silicon photodiodes 5PDI to 3) The exposure information is determined from the central part photometric value BVc, which has a fairly wide range, and the film sensitivity (SV).

2) In the case of 0.06≧α>0.04, the main subject image will be captured at a relatively large proportion (for example, the size corresponds to the photometry area of silicon photodiode 5PDI, 2), and compared to the above case. Exposure information is determined from the central portion photometric value BVc2 in a slightly narrow range and the film sensitivity (SV).

3) When 0.04≧α>0.007, the main subject image has a fairly small proportion (for example, the size corresponds to the photometric area of silicon photodiode 5PDI)
When the main subject is brighter than the background, such as when the exposure compensation amount ADJ calculated from the brightness relationship at the center is "-2" or r-IJ, the center part photometric value BVc will be taken.
2. From the information BV (BV & or Bva2) calculated from the photometric value Bv3 and the maximum brightness value Bvmax up to BV (see Figure 5) and the film sensitivity (SV), conversely, Exposure compensation amount ADJ is “1” or “2”
'', when the main subject is darker than the background, the information BV (BVa3 or BVa3 or BVa4) and film sensitivity (
Exposure information is determined from SV).

4) When 0.007≧α, the main subject is now part of the background, so exposure information is determined from center-weighted average photometry BVme and film sensitivity (SV).

According to this embodiment, the size of the main subject is determined from the distance information to the subject and the focal length information of the photographing lens, and it is predicted to which photometry region the size corresponds. If it is determined that it corresponds to the photometric area, the slope of the brightness in the center obtained by the photometric output of the 5PDI and the all light outputs of the silicon photodiodes 5PD2 and 5PD3, that is, the brightness relationship between the main subject and the background. is determined, and the exposure value at this time is determined based on the maximum or minimum value of the outputs from the silicon photodiodes 5PD1 to 7 and the central part photometric value according to the brightness relationship. Especially when the main subject image has such a large size, it becomes possible to take a photograph with more appropriate exposure. Furthermore, since all of the above operations can be performed automatically, even people who are not familiar with cameras can easily use the camera.

(Correspondence between the invention and the embodiment) In this embodiment, a silicon photodiode 5PDI
~5PD7 serves as the photometry means of the present invention, the arithmetic control circuit 33 serves as the exposure control means, and the silicon photodiode 5PDI
The photometric area by silicon photodiode 5PD2.3 is in the center photometric area, and the photometric area by silicon photodiode 5PD2.3 is in the adjacent photometric area.
They correspond to each other.

(Modified example) In this embodiment, when it is determined that the main subject image is included in the photometry area of the silicon photodiode 5PDI, the exposure value is determined by a calculation formula according to the exposure compensation amount at that time. Although the accuracy is slightly lower, if it is determined that the main subject is included in the photometric area of both silicon photodiodes 5PD1.2, the main subject obtained by the average photometric output of 5PDl and 5PD2 and the photometric output of silicon photodiode 5PD3. Even if the exposure correction amount is determined from the brightness relationship with the background and the exposure value is determined by a calculation formula based on the exposure correction amount, it is possible to provide more appropriate exposure than in the past. Also, although three photometric areas are placed at positions corresponding to the center of the shooting screen, the invention is not limited to this.
It suffices if there are at least two or more (however, the higher the number, the better the accuracy), and it is not limited to concentric circles,
They only need to be concentric, and may have a rectangular shape, for example.

In addition, although the configuration includes seven logarithmic compression diodes 2 to 8 and operational amplifiers 9 to 15, the outputs of the silicon photodiodes 5PDI to 7 are directly connected to the analog switch 16.
It is also possible to sequentially select by 22 and have only one of each. Furthermore, BVm
Judgment values (0,06, 0,04, 0,007
), or the threshold value N (0, 25) for determining the exposure correction value ADJ can be changed somewhat. Furthermore, the range of flash day synchronization warning determination may be changed somewhat.

(Effects of the Invention) As explained above, according to the present invention, when it is determined that the size of the main subject image corresponds to the central photometric area based on the distance information to the main subject and the focal length information of the photographing lens, , the maximum or minimum photometric output of all photometric areas of the photometric means, the central photometric area, and An exposure control means 5 is provided to determine the exposure value based on each output from the adjacent photometry area, and after knowing the size of the main subject image, the exposure value is determined by an exposure calculation formula equivalent to performing exposure compensation. Since it is possible to give a more appropriate exposure without deteriorating the operability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the photometry area corresponding to the shooting screen, FIG. 3 is a flowchart, and FIG. 4 is a flowchart for calculating the exposure compensation amount. , FIG. 5 is a flowchart at the time of exposure determination based on the same exposure calculation formula. 1... Shooting screen, 9-15... Operational amplifier, 16-22... Analog switch, 29
．． 30...Resistor, 31.32...Slider, 33...Arithmetic control circuit, 34-35...
...Analog switch, 38...Decoder, 39...AF control circuit, 5PD1-9PD7
...Silicon photodiode.

Claims (1)

[Claims] 1. In an exposure determining device for a camera equipped with a photometry means having a central photometric area including the center of the shooting screen and adjacent photometric areas concentrically dividing the periphery of the central photometry area at the center of the shooting screen, the distance to the main subject If it is determined that the size of the main subject image corresponds to the center photometry area based on the information and the focal length information of the photographing lens, the main subject and background obtained by each output from the center photometry area and the adjacent photometry area are determined. exposure control that determines an exposure value based on the maximum or minimum photometric output of all photometric areas of the photometric means and each output from the center photometric area and the adjacent photometric areas, depending on the brightness relationship; An exposure determining device for a camera, characterized in that it includes a means.