JPH0740109B2 - camera - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera that divides a field of view and performs photometry to determine the exposure so that a subject is properly exposed.

(Background of the Invention) As a method of determining an exposure when taking a photograph, there are roughly classified an incident light type and a reflected light type. The incident light method is one that should be measured near the main subject, which is very inconvenient for general photography. On the other hand, since the reflected light type is the easiest photometric type, all the built-in camera exposure determination devices are of this type. In this way, the advantage of using a reflected light type exposure meter in a camera is that it is easy to measure light, but it is unclear that it is affected by the reflectance of the subject and what part of the subject should be measured in what range. There is an essential problem such as being.

However, the reflected light type exposure determining device is indispensable for determining the exposure of the camera, and if the camera alone can perform the device of the method that should compensate for the above problems, the exposure can be more properly adjusted. Since it is possible to easily and automatically take a close photograph, various types of cameras have been proposed in the past in view of this point. For example, a method that automatically determines exposure based on the output from each point by performing a pre-metering operation that matches the metering point provided in the center of the shooting screen to each arbitrary point in the shooting screen (multi (Spot metering method) or a method in which the shooting screen is divided into several areas for metering, and the exposure is automatically determined based on each information such as the magnitude of the brightness or the difference (evaluation metering method). ), Etc. However, in the former type, if the person who has enough time to decide the exposure and understands that the exposure is sufficient including the reflectance of the subject is the best one, However, it is difficult for ordinary people to use, and I don't think it can be used easily by anyone. In the latter type, the usage of the camera is exactly the same as before, and as a result, better pictures can be obtained, so it can be said that it is very excellent, but the focal length of the lens used and the main subject The amount of exposure correction was set conservatively because it is not an exposure value determination algorithm after knowing the distance.

As described above, in the conventional device, it was not possible to effectively and surely know how bright or dark the main subject, which would be placed in the center of the shooting screen, was compared to the background. I couldn't easily say that it gave proper exposure.

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

(Features of the Invention) In order to achieve the above object, the present invention is divided into a first region including at least a focus detection region and an outer region outside the first region, and detects the brightness of each region. Brightness detecting means, a magnification detecting means for obtaining information corresponding to a photographing magnification of the photographing object by a distance to the photographing object and a focal length, and when the information detected by the magnification detecting means is within a specific range. Is provided with a calculation unit that performs photometric calculation including information on a difference between the brightness of the first region and the brightness of the outer region detected by the brightness detection unit.

(Examples of the Invention) Hereinafter, the present invention will be described in detail based on illustrated examples.

1 and 2 are views showing an embodiment of the present invention. SPD1 ~ SP7
Is a silicon photodiode that constitutes a light sensor for measuring the field brightness in a divided pattern corresponding to the photographic screen 1 as shown in FIG. 2, 2 to 8 are logarithmic compression diodes, and 9 to
Reference numeral 15 is an operational amplifier, 16 to 22 are analog switches which are turned on / off according to a signal from a decoder described later, 23 is an operational amplifier, 24 is a diode, and a diode for logarithmic compression is provided together with a constant current source 25 for flowing a forward current Iref to the diode 24. A circuit for compensating the reverse saturation current of 2 to 8 is configured.
Reference numeral 26 denotes an operational amplifier, a resistor 28 and a resistor having a temperature coefficient for temperature compensation of the logarithmic compression diodes 2 to 8 and the diode 24, 29 and 30 resistors fixed to the taking lens barrel, and 31 a distance of the taking lens. A slider that slides on the resistor 29 in conjunction with the rotation of the ring, and a voltage (a voltage obtained by dividing the reference voltage Vref) corresponding to the focus position of the photographing lens is generated on the slider 31. . Reference numeral 32 denotes a slider that slides on the resistor 30 in association with the rotation of the zoom ring of the photographing lens.
At 32, a voltage (a voltage obtained by dividing the reference voltage Vref) that depends on the zoom position (focal length) at that time is generated.

33 is an arithmetic control circuit having an arithmetic function and various control functions, 34
36 are analog switches that are turned on and off according to the signal from the arithmetic control circuit 33, and 37 are analog switches 34 to 34.
An A / D conversion circuit for converting an analog signal input via 36 into a digital signal, 38 a decoder for selecting (turning on) the analog switches 16 to 22 in accordance with the signal from the arithmetic control circuit 33, 39 an infrared ray A motor 40 drives a photographing lens to a focus position based on a distance detection unit including a light emitting diode and a light receiving element that receives reflected light of the infrared light from a subject and a distance signal obtained by the distance detection unit. An AF control circuit equipped with a drive control unit, 41 is a first release button
It is a switch that turns on with a stroke.

Next, the operation according to the flowcharts of FIGS. 3 and 4 will be described. The first stroke of the release button is performed and the switch
When 41 is turned on, the arithmetic and control circuit 33 turns the analog switch
When 35 is turned on, an operation start signal is output to the AF control circuit 39. Then, the distance detection unit in the AF control circuit 39 starts the operation of obtaining the distance signal to the main subject located at the center of the shooting screen. On the other hand, a voltage corresponding to the rotational position of the distance ring of the photographing lens is generated in the slider 31, and this signal is input to the A / D conversion circuit 37 via the analog switch 35,
After being converted into a digital signal, it is input to the drive control section of the AF control circuit 39 via the arithmetic control circuit 33. When the distance signal and the position signal of the distance ring are input, the drive control unit in the AF control circuit 39 determines whether or not the AF is successful based on the information, and when it is determined that the AF is successful, the motor 40 is driven. Control the
That is, the rotation direction and speed of the motor 40 are controlled to move the taking lens to the in-focus position, and if not successful, the taking lens is moved to the infinite position. It should be noted that the case of not being successful here is, for example, when the contrast of the subject is low or when the subject is located at a distant place, depending on the AF method. After that, when it is determined that the photographing lens has finished focusing or has moved 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 indicating that the taking lens (distance ring) is stopped, and simultaneously turns off the analog switch 35 and turns on the analog switch 36 this time. When the analog switch 36 is turned on, a voltage corresponding to the rotational position of the zoom ring generated by the slider 32 is applied to the A / D conversion circuit 37 via the switch.
To the arithmetic control circuit 33 after being converted into a digital signal, and the signal is stored together with the position signal of the photographing lens. As a result, the arithmetic control circuit 33 stores the distance information D corresponding to the distance from the main subject to the camera and the focal length information f of the photographing lens, and the arithmetic control circuit 33 determines the subject based on these information. Magnification α
It is calculated from the equation α = f / D. Also the analog switch 3
Turn off 6 and turn on analog switch 34,
The analog switches 16 to 22 are sequentially turned on via the decoder 38, and the photometric signals of the silicon phototransistors SPD1 to SPD7 output from the operational amplifiers 9 to 15 are supplied to the operational amplifiers 23, 27,
Input through the analog switch 34 and the A / D conversion circuit 37, etc., and the brightness values BV _{1 to} BV ₇ corresponding to each are obtained.

Next, the arithmetic and control circuit 33 uses the brightness values BV _{1 to} BV ₇ to determine the central weighted average photometric value BVme and two types of central partial photometric values BVc ₁ and BV.
Vc ₂ is calculated by the following formula.

_{BVme = (2BV 1 + BV 2} + BV 3 + BV 4 + BV 5 + BV 6 + BV 7) / 8 BVc 1 = (3BV 1 + 2BV 2 + BV 3) / 6 BVc 2 = (2BV 1 + BV 2) / 3 then the center as shown below Brightness of parts (brightness values BV _{1 to} BV ₃ )
The exposure compensation amount ADJ is obtained from the relationship. Note that N (= 0.2
5) is a threshold value for obtaining the exposure correction amount ADJ.

1) The relationship of BV ₁ -BV ₂ > N and BV ₂ -BV ₃ > N, that is, when it is determined that the main subject is considerably brighter than the background, the exposure correction amount ADJ is set to "-2".

2) BV ₂ −BV ₁ > N and BV ₃ −BV ₂ > N, that is, when it is determined that the main subject is considerably darker than the background, the exposure correction amount ADJ is set to “+2”.

3) BV ₁ -BV ₂ > N and BV ₁ -BV ₃ > N, that is, when it is determined that the main subject is slightly brighter than the background, the exposure correction amount ADJ is set to "-1".

4) The relationship of BV ₁ −BV ₃ > N and BV ₂ −BV ₃ > N, that is, when it is determined that the main subject is slightly brighter than the background as in 3), the exposure correction amount ADJ is “−1”. And

_{5) BV 2 -BV 1> N} , and BV ₃ -BV _1> relationship N, exposure compensation amount if That main object is determined a little darker than the background
Set ADJ to “+1”.

6) The relationship of BV ₃ −BV ₁ > N and BV ₃ −BV ₂ > N, that is, when it is determined that the main subject is slightly darker than the background as in 5), the exposure correction amount ADJ is set to “+1”. To do.

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".

Further, the center-weighted average photometry value BVme is larger than a certain minimum brightness value BVst required for strobe daytime synchronization, and the distance information D to the main subject is smaller than the maximum distance information Dst reached by the strobe light, and When the value of the exposure compensation amount ADJ is "+2" (when there is strong backlight), a warning signal is issued indicating that it is better to perform strobe daytime synchronization.

Next, the arithmetic control circuit 33 determines the proportion of the main subject image to the photographic screen 1 according to the subject magnification α obtained by the equation α = f / D, that is, the size of the photometric area to which the main subject image corresponds. Predict if there is a central photometric value BVc ₁ ,
BVc ₂ , center-weighted average photometric value BVme or exposure compensation amount AD
Select one of the photometric values calculated based on J, and determine the aperture value AV and shutter speed TV values by the exposure program diagram from the information BV and film sensitivity (SV).
That is, the exposure information is determined. In other words, 1) When α> 0.06, the ratio of the main subject image to the photographing screen 1 is considerably large (assuming that the main subject is a human face, for example, the size corresponding to the photometric areas of the silicon photodiodes SPD1 to SPD3 ), The central part metering value BV in a fairly wide range
Determine the exposure information from c ₁ and the film speed (SV).

2) When 0.06 ≧ α> 0.04 The main subject image is captured at a relatively large ratio (for example, the size corresponding to the photometric area of the silicon photodiodes SPD1 and 2), which is slightly narrower than the above case. Exposure information is determined based on the central photometric value BVc ₂ and the film sensitivity (SV).

3) When 0.04 ≧ α> 0.007 The main subject image is captured at a fairly small ratio (for example, the size corresponding to the photometric area of the silicon photodiode SPD1). It is better to decide the exposure so that the exposure compensation is applied to the average photometry value. Therefore, as described above, the exposure correction amount ADJ obtained from the relationship of the brightness of the central portion is set as the correction amount for the center-weighted average photometric value. Thus, the exposure information is determined from the information (BVme-ADJ) and the film speed (SV).

4) When 0.004 ≧ α Since the main subject is already a part of the background, the exposure information is determined from the center-weighted average photometry BVme and the film sensitivity (SV).

According to the present embodiment, the size of the main subject is obtained from the distance information to the subject and the focal length information of the photographing lens to predict which photometric region the size corresponds to, and as a result, the silicon photodiode SPD1 When it is determined that it corresponds to the photometric area, the amount of inclination of the central brightness obtained by the photometric output of the SPD1 and each of the photometric outputs of the silicon photodiodes SPD2 and SPD3, that is, the relationship between the brightness of the main subject and the background Obtain the exposure compensation amount from the silicon photodiode SPD1 ~
Since the value obtained by adding the exposure correction amount to the center-weighted average photometric value obtained from 7 is output as the exposure value at this time, it is possible to take a photograph with a more appropriate exposure. Also, since all the above operations can be performed automatically,
Even people who are not familiar with cameras can easily use it.

(Correspondence between Invention and Example) In this example, the silicon photodiodes SPD1 to SPD are used.
D7 in the brightness detection means of the present invention, low antibody 29,30, sliders 31,32, A / D conversion circuit 37 and operation control circuit 33 in the magnification detection means, operation control circuit 33 in the operation means, respectively. Equivalent to.

(Modification) In this embodiment, the main subject image is a silicon photodiode.
When it is determined that the photometric area corresponds to SPD1, the exposure value is determined from the center-weighted average photometric value and the exposure compensation amount. When it is determined that the area corresponds to the area, the optimum exposure amount is obtained from the brightness relationship between the main subject and the background obtained by the average photometric output of SPD1 and SPD2 and the photometric output of the silicon photodiode SPD3, and this value and the center-weighted average. Even if the exposure value at this time is determined based on the photometric value, the proper exposure can be provided as compared with the conventional case. Further, although three concentric photometric regions are arranged at positions corresponding to the center of the photographing screen, the number is not limited to this, and it is sufficient if at least two photometric regions are provided (however, more is better for accuracy). Will be). Further, the shape is not limited to the concentric circle shape, and may be a square shape as long as the shape is concentric.

Also, the configuration is provided with seven logarithmic compression diodes 2 to 8 and operational amplifiers 9 to 15, but the outputs of the silicon photodiodes SPD1 to 7 are directly selected by the analog switches 16 to 22, and one of each is selected. It is also possible to provide only the structure. Furthermore, BVme, BVc _1, each constant and determined values by the object magnification α for obtaining the BVc ₂ (0.06,
0.04, 0.007) or exposure compensation value AD
It is possible to change the threshold value N (0.25) in determining J to some extent. Further, the range of strobe daytime sync warning determination may be changed to some extent.

(Effects of the Invention) As described above, according to the present invention, the first area including at least the focus detection area and the outer area outside the first area are divided, and the brightness of each area is detected. Brightness detecting means, a magnification detecting means for obtaining information corresponding to a photographing magnification of the photographing object by a distance to the photographing object and a focal length, and when the information detected by the magnification detecting means is within a specific range. Since the calculation means for performing the photometric calculation also includes information on the difference between the brightness of the first area and the brightness of the outer area detected by the brightness detection means, without deteriorating the operability, More proper exposure can be given.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a photometric area corresponding to the photographing screen, FIG. 3 is the same flowchart, and FIG. 4 is a flowchart for similarly calculating the exposure correction amount. Is. 1 ... Shooting screen, 9-15 ... Operational amplifier, 16-22 ... Analog switch, 29, 30 ... Low antibody, 31, 32 ... Slider, 33 ... Arithmetic control circuit, 34-35 ... Analog switch, 38 ... Decoder, 39 ... AF control circuit, SPD1 to SPD7 ...
… Silicon photodiodes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Yamada Akira Yamada 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) References JP-A-56-89029 (JP, A) JP-A-56 -98626 (JP, A) JP-A-61-279829 (JP, A)

Claims (1)

[Claims] 1. A first area including at least a focus detection area and a brightness detecting means which is divided into an outer area outside the first area and detects the brightness of each area, and a distance to an object to be photographed. Magnification detecting means for obtaining information corresponding to the photographing magnification of the object to be photographed by the focal length, and when the information detected by the magnification detecting means is within a specific range, the first detecting means detected by the luminance detecting means. A camera provided with a calculation means for performing a photometric calculation including information on a difference between the brightness of the area 1 and the brightness of the outer area.