JPH045972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for dividing a field into a plurality of regions, applying side lighting, and determining the appropriate exposure of the entire screen from a plurality of photoelectric outputs corresponding to the plurality of regions. The present invention relates to a multi-photometering device that outputs photometering output.

Japanese Patent Publication No. 47-33794 describes a photometry method in which the entire surface to be photometered is divided into appropriate small areas, and the geometric mean value, maximum value, minimum value, contrast, arithmetic mean value, etc. are obtained from the photometric values of each area. is disclosed.

This photometry method is extremely effective as a method for obtaining photometry data that serves as the basis for determining the desired exposure amount for subjects with various brightness distributions and for various purposes. However, this photometry method is limited to simply obtaining photometric values, and it is up to the photographer to decide what kind of exposure to give based on the obtained photometric values. Therefore, since this judgment requires skill, it is not suitable for general photographers (beginners, etc.).

An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide a multi-photometering device that is capable of automatically obtaining appropriate exposure based on a plurality of photometry outputs corresponding to a plurality of photometry areas obtained by dividing the field of view. It is about providing.

First, the basic principle of the present invention will be explained.

1A to 1D show the relationship between the luminance range of various scenes and the latitude of the film, where the horizontal axis is luminance (unit: apex BV).

In the various scenes shown in FIGS. 1A to 1D, the brightness to which exposure should be adjusted to obtain proper exposure is as follows.

(1) In the case of a scene where the difference between the maximum brightness BVmax and the minimum brightness BVmin is very large as shown in Figure 1a, and includes a high-brightness subject such as the sun and a low-brightness subject such as the shadow of a tree: In this case, it is extremely rare for the main subject to exist at the extremes of the high-brightness side and the low-brightness side.
If the main subject exists, it often exists at medium brightness or lower brightness. On the other hand, when exposure is set to medium brightness, there is a possibility that objects at lower brightness will appear dark and blurred.

Therefore, in consideration of the latitude L of the film, it is preferable that the brightness at which the exposure should be adjusted be around the middle between the medium brightness and the lowest brightness. In this way, the subjects with the highest and lowest brightness will appear brighter,
Although the image may be dark and blurred, it is possible to obtain a photograph in which subjects with medium to relatively low brightness are properly exposed. To express this specifically, the average value of maximum brightness BVmax and minimum brightness BVmin
When BVmean is set to medium brightness, the brightness at which the exposure is adjusted is given by a value near the middle between medium brightness and minimum brightness, for example, (BVmean+BVmin)/2.

In addition, in a multi-photometering device that divides the field into multiple areas and measures the light, each light-receiving element is responsible for metering the field of a certain size, but at this time, the light output of each side is There is a tendency for the bright areas of the subject to exhibit characteristics. For this reason, it is necessary to adjust the exposure to (BVmean+BVmin)/2 in order to avoid darkening low-brightness subjects.

(2) As shown in Figure 1b, the difference between the maximum brightness BVmax and the minimum brightness BVmin is relatively large, and although there is no subject with extremely different brightness and darkness, such as a landscape that includes the sky on a clear day, the contrast is In the case of a bright scene; in this case, the entire screen must be properly exposed, such as a general landscape photograph or a commemorative photograph with a landscape in the background, and the brightness at which the exposure should be matched must be set in the foreground. Or, in many cases, it is not possible to focus on either the background. In other words, this is a scene in which the main subject intended by the photographer exists, but the exposure cannot be adjusted to only this subject.

In such a case, if the average value BVmean is used as the brightness at which the exposure should be adjusted, it is possible to obtain a photograph in which the entire screen including the maximum brightness side is properly exposed due to the latitude L of the film.

In this case, the photometric output of each photoreceptor of the multi-photometer is biased toward the bright areas, but since the exposure needs to match both the high-brightness and low-brightness sides, the high-brightness areas should be adjusted to the latitude L of the film. There is no need to emphasize the low luminance side even if it is outside the range of .

(3) As shown in Figure 1 c, the difference between the maximum brightness BVmax and the minimum brightness BVmin is relatively small, for example, in a scene that includes the open sky; in this case, case (2) differs from maximum brightness
Since BVmax and the minimum brightness BVmin are within the latitude L of the film, the brightness at which the exposure should be adjusted may be BVmean. At this time, since each light-receiving element has the above-mentioned characteristics, this is allowed only when the difference in brightness between objects existing in the field covered by each light-receiving element is not very large.

However, depending on the scene, there may be a large difference in brightness between subjects existing there. In other words, there is a time when sufficient low-luminance information cannot be obtained with a finite number of light receiving elements. In this case, it is preferable to set the exposure to (BVmean+BVmin)/2 so that the low-luminance subject does not become too dark. Considering these things, it can be said that it is necessary to adjust the exposure within the range of (BVmean + BVmin)/2 from BVmean.

(4) In the case of a fairly flat scene with very little brightness difference, as shown in Figure 1d; in this case, both the high and low brightness sides are included in the range of latitude L of the film;
Considering that the photometric output of each photodetector is biased toward bright areas as mentioned earlier, the brightness at which the exposure should be adjusted is (BVmean +
BVmin)/2 to BVmin. In this way, it is possible to prevent a low-luminance subject from appearing too dark.

FIG. 2 is an explanatory diagram showing the relationship between the difference between the maximum brightness BVmax and the minimum brightness BVmin and the brightness (indicated by dotted lines) at which exposure should be adjusted. As can be seen from this, the difference between a maximum brightness and minimum brightness (BVmax−BVmin=
dBV) is very small, from BVmin
b for the brightness of the value near the middle between BVmean and BVmin
When dBV becomes very large, it becomes almost BVmean.
If you adjust the exposure to the brightness around the middle of BVmin and the brightness between BVmean and BVmin when c dBV is between the above two, you can obtain the appropriate exposure for each subject. can. This principle is not purely theoretical, but is an empirical and statistical one obtained through actual photography, and the point is that the brightness at which the exposure should be adjusted is determined based on the difference between the maximum and minimum values. There are characteristics.

FIG. 3 shows an example of a light receiving element used in the present invention. The light receiving element 1 is a two-dimensional image sensor such as a photodiode array or a CCD. In the figure, it is a 4x6 matrix, and photometry can be performed by dividing the screen into 24 parts.

Figure 4 shows _an example of _the light receiving element ₁ when the number of screen divisions is _reduced . ), can be obtained as corresponding to the lower right corner of the screen (PV ₄ ).

FIG. 5 shows an example of mounting the light receiving element 1. The object light reaches the fan-inspection optical system 7 via the lens 2, the aperture 3, and the mirror 4. The object image is then formed on the light receiving element 1 by the imaging lens 8. 5
6 is a focal plane shutter, and 6 is a film.

FIG. 6 is a block diagram (not an embodiment of the present invention) showing an example configured to satisfy the characteristics shown in FIG. 2. The photometry circuit 10 includes the light receiving element 1 shown in FIG.
Outputs PV ₀ to PV ₄ . These outputs correspond to the brightness BV ₀ to BV ₄ (apex value) of each part of the divided screen, and the maximum aperture of the lens AV ₀ (apex value).
The figure has decreased by the same amount. That is, PV ₀ = BV ₀ − AD ₀ PV ₁ = BV ₁ − AV ₀ 〓 PV ₄ = BV ₄ − _{AV 0} . The brightness calculation unit 11 calculates a plurality of side light outputs PVj=BVj−AV ₀ (where j=0 to
4) and the maximum aperture value of the lens from the information setting section 12
AV ₀ and are added to obtain the absolute brightness BVj.
The maximum value output circuit 13 outputs the maximum value in BVj.
Output BVmax. The average value output circuit 14 is BVj
Outputs the average value BVmean. The minimum value output circuit 15 outputs the minimum value BVmin among BVj.
The intermediate value output circuit 16 receives the outputs of the circuits 14 and 15 and outputs (BVmean+BVmin)/2. The differential circuit 17 outputs an output dBV of the difference between the maximum value BVmax and the minimum value BVmin. Comparison circuits 19-21
One of the comparison circuits outputs a logical value "1" according to the difference output dBV and a predetermined reference level. Switches 22-24 are comparison circuits 18-21
BVmean, BVmin, (BVmean+
BVmin)/2 is selectively output.

Next, the operation will be explained using specific values of dBV.

(1) When dBV>5; the comparator circuit 18 outputs “1”, the output of OR1 becomes 1, and switch 2
Apply to 3. The other comparison circuits output "0". Therefore, only the switch 23 is turned on and the output of the intermediate value output circuit 16 (BVmean
+BVmin)/2 appears at the output terminal.

(2) When 3<dBV≦5;,: The comparison circuit 19 outputs “1” and applies it to the switch 22. Since the outputs of the other comparison circuits are "0", only the switch 22 is turned on, and the average value output circuit 1
The output BVmean of 4 appears at the output terminal.

(3) When 5/3<dBV≦3: Since the comparison circuit 20 outputs “1” and the other comparison circuits output “0”, the output of OR1 becomes 1 and only the switch 23 is turned on. Therefore, the output (BVmean+BVmin)/2 of the intermediate output circuit 16 appears at the output terminal.

(4) When dBV≦5/3; comparison circuit is 21 “1”
Since the other comparison circuits output "0", only the switch 24 is turned on. Therefore,
The output BVmin of the minimum value output circuit 15 appears at the output terminal.

The luminance output selected in this manner is input to a well-known apex calculation circuit, where an appropriate exposure value is calculated together with the ground exposure factor. This appropriate exposure value is input to an exposure control circuit and/or a display circuit to perform automatic exposure control and display.

Here, it is preferable to use normal comparators for the comparison circuits 18 and 21, and window comparators for the comparison circuits 19 and 20.

FIG. 7a shows a circuit example of the maximum value output circuit 13, and FIG. 7b shows a circuit example of the minimum value output circuit 15. These are circuits that are known per se, using op-amps and diodes.

FIG. 8 is a circuit example of the average value output circuit 14 composed of resistors r, r/n and an OP amplifier _A1 . In this circuit, the average value of the photometric outputs is obtained not from the maximum value BVmax and the minimum value BVmin, but from all the photometric outputs.

FIG. 9 is a circuit example of the intermediate value output circuit 16,
It is composed of followers _A10 to _A12 and voltage dividing resistors _R1 to _R4 .

FIG. 10 is a block diagram showing only one embodiment of the invention. In this embodiment, the selection operation of the brightness at which the exposure should be adjusted in the example of FIG. 6 is partially modified in accordance with the brightness state at the center of the screen. That is, it determines whether the center of the screen is close to the maximum brightness when 5/3<dBV≦3 and whether the center of the screen is close to the minimum brightness when dBV≦5/3, and corrects the brightness at which the exposure should be adjusted. It is something.

The operation will be explained below.

(1) The first determination circuit 25 inputs the brightness BV ₀ at the center of the screen and the maximum brightness BVmax, and determines whether the brightness BV ₀ satisfies the condition BV ₀ ≧ BVmax - a (a...constant). . When this condition is satisfied, the main subject is often in the center of the screen, so the brightness at which the exposure should be adjusted is determined from (BVmean + BVmin) / 2.
Correct it to (BVmax+BVmean)/2. That is, at this time, since both the comparison circuit 20 and the first discrimination circuit 25 output "1", the AND gate AND outputs "1" and turns on the switch 27. Then, the output (BVmax+BVmean)/2 of the intermediate value output circuit 28 appears at the terminal.
On the other hand, since the rotation circuit NOT1 outputs "0", the AND gate AND2 outputs "0", and the other comparison circuits 18, 19, and 21 output "0", so the switches 22 to 24 are turned on. It will never become.

On the other hand, when the above-mentioned conditions are not satisfied, the first discrimination circuit 25 outputs "0", and therefore the AND gate AND2 outputs "1".
Therefore, (BVmean+BVmin)/2 is selected.

This operation is performed because, in a scene where the comparator circuit 20 outputs "1", when the center of the screen is bright, where there is a high possibility that the main subject exists, the exposure is adjusted to this. (Do not set the brightness too high)
This is because there is a high possibility that it matches the photographer's intention.

(2) The second determination circuit 26 inputs the brightness BV ₀ at the center of the screen and the minimum brightness BVmin, and determines whether the brightness BV ₀ satisfies the condition BV ₀ ≦BVmin+a. When this condition is satisfied, it means that the center of the screen is dark. Since there is generally a high possibility that the main subject is present in the center of the screen, it can be determined that the subject is backlit in this case. Therefore, the brightness at which exposure should be adjusted is BVmin. That is, since both the comparison circuit 21 and the second discrimination circuit 26 output "1" at this time, the AND gate AND3 outputs "1" and turns on the switch 24.

On the other hand, if this condition is not satisfied, the comparator circuit 21 outputs "1", and the second discriminator circuit 26 outputs "1".
outputs “0”, so the AND gate AND3
outputs “0” and AND4 outputs “1”. Therefore, the switch 23 is turned on (BVmean+
BVmin)/2 is selected.

To perform the above operations (1) and (2),
The reason why this was done only when dBV≦5 and dBV≦5/3 was done is because in the case of the subject under other conditions, it is often meaningless to limit the exposure to the center of the screen due to the nature of the subject. It is.

As described above, according to the present invention, in a multi-photometering device that divides a field into photometers and obtains a plurality of photometry outputs corresponding to each area, the difference between the maximum value and the minimum value of the plurality of photometry outputs is If the photometric output at the center of the subject is smaller than the predetermined value and is relatively large, the first value located between the average value and the maximum value of the plurality of photometric outputs, and the maximum value and the minimum value. Similarly, if the difference from the first value is smaller than a predetermined value and the photometric output at the center of the field is relatively small, a second value smaller than the first value is set as a single value for calculating the appropriate exposure. Since the exposure can be automatically adjusted to the main subject to be photographed, it is possible to obtain a photometry device that does not require any skill in determining exposure.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the relationship between the luminance range of various scenes and the latitude of the film, Fig. 2 is an explanatory diagram showing the relationship between the luminance difference and the luminance at which exposure should be adjusted, and Figs. 3 and 4 are illustrations of the present invention. Fig. 5 is a schematic diagram showing the photometric optical system of the present invention, Fig. 6 is a block diagram showing an example configured to satisfy the characteristics shown in Fig. 2, Fig. 7 9 are diagrams showing specific circuit examples of the blocks shown in FIG. 6, and FIG. 10 is a block diagram showing the only example of the circuit for implementing the present invention. [Explanation of symbols of main parts], 10...photometering circuit,
11... Brightness calculation unit, 13... Maximum value output circuit,
14...Average value output circuit, 15...Minimum value output circuit, 16...Intermediate value output circuit, 17...Differential circuit, 19-21...Comparison circuit.

Claims (1)

[Scope of Claims] 1. A multi-photometering device that measures at least a central area of a field and a plurality of peripheral areas located around the central area, and obtains a plurality of photometric outputs corresponding to each area, comprising: The maximum value among the photometric outputs (BV _nax )
maximum value detection means 13 for detecting the minimum value (BV _nio ) from among the plurality of photometric outputs;
a minimum value detection means 15 for detecting a substantially average value (BV _neao ) from among the plurality of photometric outputs; an average value detection means 14 for detecting an approximately average value (BV _{neao )} from among the plurality of photometric outputs; a first intermediate value calculation means 28 for calculating a first intermediate value located between the minimum value (BV _nio ) and the average value (BV _neao ); intermediate value calculation means 16, the maximum value (BV _nax ) and the minimum value (BV _nio );
a brightness difference detection means 17 for detecting the difference (dBV) between the brightness difference (dBV) and the first predetermined value (dBV=
5) and generates a first output when the luminance difference is larger; the luminance difference (dBV) and the first predetermined value (dBV=5); A second predetermined value (dBV=3) smaller than the first predetermined value is compared, and if the luminance difference is less than or equal to the first predetermined value and greater than or equal to the second predetermined value, the second output is output. Second comparison means 1 that occurs
9. Compare the brightness difference (dBV) with the second predetermined value (dBV=3) and a third predetermined value (dBV=5/3) smaller than the second predetermined value, and calculate the brightness difference. is less than or equal to a second predetermined value and greater than or equal to a third predetermined value, a third comparison means 20 generates a third output, and the photometric output (BV _p ) regarding the central region is proportional to the maximum value. a determining means 25 that determines that it is larger than a first relative value (BV _nax −a ₋ ) and generates a fourth output, selects the second intermediate value when the first output is generated; The average value is selected when the second output occurs, the second intermediate value is selected when the third output occurs and the fourth output does not occur, and the third output is selected. occurs and the fourth output occurs, the first
photometric output generating means 22, 23, 27, AND1, AND2, NOT which selects the intermediate value of and outputs it as a single photometric output for calculating the respective appropriate exposure;
1. A multi-photometering device characterized by being equipped with OR2.