JP4539276B2 - Camera photometric device and camera - Google Patents

Description

  The present invention relates to a photometry device of a camera that performs photometry on a subject.

A number of improved techniques have been proposed in the past for photometry devices that divide a subject field into a plurality of areas and perform photometry, analyze luminance information of each divided area, and control the exposure of the camera. For example, in Patent Document 1, the screen is divided into a plurality of areas, and the difference between the first exposure value based on the photometric value of each area and the maximum value in the photometric value is obtained. An automatic exposure apparatus that employs a second exposure value that is brighter than the exposure value is disclosed. Patent Document 2 discloses a camera that controls exposure by discriminating a scene based on a correlation between a luminance distribution of a subject and a histogram template.
JP 2001-45363 A Japanese Patent Laid-Open No. 2003-174583

  In Patent Document 1, when the difference between the first exposure value and the maximum value in the photometric value is small, it is determined that the scene is whitish and the exposure value is corrected brightly. However, in Patent Document 1, when the high-luminance portion is small with respect to the photometric area in which the maximum value is detected and the brightness difference in the photometric area is large, the detected maximum value (average value in the photometric area). The actual maximum may be greater than In such a situation, if the detected first value is trusted and the first exposure value is raised brightly, the high-luminance portion may be saturated and white stripes may occur. For this reason, in Patent Document 1, there is a restriction that even if the first exposure value is increased brightly, a large correction cannot be performed.

  On the other hand, in Patent Document 2, for example, even with the same luminance distribution, a scene with many small high-luminance portions (such as a subject that has received a sunlight through a tree) and a scene with high-luminance portions having a certain degree of clustering (in the shade But it is difficult to distinguish both from the histogram. In particular, when the main subject has a high luminance part in the latter scene, exposure control that does not saturate the high luminance part is desired, and there is still room for improvement in that respect.

  The present invention is for solving the above-mentioned problems of the prior art, and its purpose is to obtain a more appropriate exposure in consideration of the brightness of the scene and the size of the high-luminance portion of the object scene. It is to provide a photometric device for a camera.

Photometric apparatus of the camera according to the present invention, a photometric unit that detects photometric values for each of the plurality of divided regions, and grouping the plurality of divided regions into a plurality of groups, the photometry of the divided regions included in the group a first calculator for calculating a luminance value of the object scene based on the values, the maximum photometry value detector for detecting a maximum photometry value is the maximum photometric values from the plurality of divided regions, the maximum photometry value A high-luminance range detector that detects a size of a range in which the photometric value equal to or greater than a threshold value is detected continuously from the detected divided area; and a size of the range detected by the high-luminance range detector ; And a second arithmetic unit that changes the luminance value using a value corresponding to the difference between the maximum photometric value and the luminance value .

The second calculation unit compares the size of the range detected by the high luminance range detection unit with a predetermined first threshold, and corresponds to the difference between the maximum photometric value and the luminance value. The value to be compared may be compared with a predetermined second threshold value, and the luminance value may be changed so that the exposure amount increases .
Further, the second calculation unit is configured such that a difference between the maximum photometric value and the luminance value is larger than a predetermined value, and the divided area where the maximum photometric value is detected is located near the center of the screen, and the high luminance range detection is performed. When the size of the range detected by the unit is equal to or greater than a predetermined threshold, the luminance value may be changed so that the exposure amount is reduced.

In addition, the high luminance range detection unit may detect the size of the range by counting the total number of the divided areas in which the photometric value equal to or greater than the threshold is detected .
Further, the high-luminance-range detector may calculate the magnitude of the range using the plurality of line segments to the intersection of the division area where the maximum photometry value is obtained.
The camera according to the present invention includes any one of the photometric devices according to the present invention .

In the present invention , the brightness value is changed using the size of the range detected by the high brightness range detection unit and the value corresponding to the difference between the maximum photometric value and the brightness value. Appropriate exposure reflecting the size of the high luminance portion can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Description of the first embodiment)
FIG. 1 is a diagram showing an electronic camera according to a first embodiment in which a camera photometry device according to the present invention is incorporated.
The electronic camera according to the first embodiment includes a camera body 1 and a lens unit 2 in which a photographing lens 2a is accommodated. Here, the lens unit 2 is attached to the camera body 1 in a replaceable manner. The camera body 1 also includes a quick return mirror 3 that can be switched between an observation position and a retracted position, a focal plane shutter 4, an image sensor 5 that photoelectrically converts a subject image, an optical finder system, and re-image formation for photometry. The lens 6, the split photometry element 7, and the control unit 8 are included.

  The quick return mirror 3, the focal plane shutter 4, and the image sensor 5 are arranged along the optical axis of the photographing lens 2 a, and the optical finder system is arranged in the upper region of the quick return mirror 3. Here, the quick return mirror 3 at the observation position intersects the photographing optical path from the photographing lens 2a to the image sensor 5, and reflects the light beam that has passed through the photographing lens 2a upward to guide it to the optical finder system. .

  On the other hand, the quick return mirror 3 in the retracted position is in a state of being flipped upward from the observation position. When the quick return mirror 3 is in the retracted position, the light beam that has passed through the photographic lens 2 a is guided to the focal plane shutter 4 and the image sensor 5, and photographic image data of the subject is generated based on the image signal of the image sensor 5. be able to. The central portion of the quick return mirror 3 is a half mirror that transmits light. Then, a part of the light beam that has passed through the quick return mirror 3 at the observation position is refracted downward by the sub mirror and guided to the focus detection unit (illustration of the sub mirror and the focus detection unit is omitted).

  The optical finder system has a diffusion screen 9, a condenser lens 10, a pentaprism 11, and an eyepiece lens 12. The diffusing screen 9 is disposed above the quick return mirror 3 and once forms an image of the light beam reflected by the quick return mirror 3 at the observation position. The light beam formed on the diffusing screen 9 passes through the condenser lens 10 and the pentaprism 11 and reaches the eyes of the photographer through the eyepiece lens 12.

  The photometry re-imaging lens 6 and the split photometry element 7 are arranged in the vicinity of the pentaprism 11. The photometric re-imaging lens 6 re-images part of the light beam imaged on the diffusing screen 9, and the split photometry element 7 executes split photometry of the re-focused finder image. Here, the divided photometric element 7 of the first embodiment can detect the photometric value of each divided area by dividing the object scene into 64 (8 × 8) (see FIG. 2).

For example, the control unit 8 controls drive control of the imaging mechanism, control of image processing related to generation of captured image data, and the like. Further, the control unit 8 performs an exposure calculation of the electronic camera based on the output of the divided photometric element 7, and controls the exposure at the time of photographing based on the calculation result.
Here, the control unit 8 groups the divided areas of the divided photometric element 7 from the first group to the fifth group, and the object field based on the photometric values (G [1] to G [5]) for each group. Is calculated (see FIG. 3). And the control part 8 determines the exposure amount at the time of imaging | photography based on the luminance value BvAns.

Further, the control unit 8 detects the maximum photometric value Bmax in the 64 divided areas of the divided photometric element 7 and the size (MaxAmt) of the divided area where the maximum photometric value Bmax is obtained. Then, the control unit 8 changes the luminance value BvAns when the maximum photometric value Bmax and the size of the divided region group (MaxAmt) satisfy a predetermined condition.
The electronic camera according to the first embodiment is configured as described above, and the exposure calculation operation will be described below with reference to the flowchart of FIG.

Step S1: The control unit 8 detects the photometric value of each divided area divided into 64 based on the output of the divided photometric element 7. Note that the notation of the photometric value of each divided region in this specification is, for example, B [h, v if it is a photometric value of the divided region in the vth row and hth column with the lower left of the divided photometric element 7 as a base point. ].
Step S2: The control unit 8 calculates the group photometric values (G [1] to G [5]) of the first group to the fifth group based on the photometric values detected in step S1 by the following equation (1). . Each group is composed of 16 (4 × 4) divided regions, and the first group located in the center is set so as to overlap the second group to the fifth group (see FIG. 3). .

ただし、式（１）において、ＳＵＭ（Ｂ［ｘ１，ｙ１］．．Ｂ［ｘ２，ｙ２］）は分割領域［ｘ１，ｙ１］，［ｘ２，ｙ１］，［ｘ１，ｙ２］，［ｘ２，ｙ２］が４隅となる矩形範囲（グループ）の測光値の合計を返す関数である。

However, in the formula (1), SUM (B [x1, y1]... B [x2, y2]) is divided regions [x1, y1], [x2, y1], [x1, y2], [x2, y2 ] Is a function that returns the total photometric value of a rectangular range (group) having four corners.

  Step S3: The control unit 8 compares each group photometric value (G [1] to G [5]) in step S2 with a predetermined luminance Lbv. If any of the group photometric values is equal to or higher than the predetermined luminance Lbv, the control unit 8 replaces the group photometric value with the predetermined luminance Lbv and performs clipping. For example, when the sun is included in a photometry area of a certain group, the upper limit value of the group photometry value is cut by the operation of step S3.

  Step S4: Based on the group photometric values G [1] to G [5], the control unit 8 determines the average luminance value BvMean, the central luminance BvC, the maximum luminance BvMax, the minimum luminance BvMin, the upper part of the screen and the lower part of the screen. Information that is characteristic of the subject, such as the luminance difference dHE, is calculated by the following equation (2).

ただし、式（２）において、ＭＡＸ（ｘ［１］．．ｘ［ｎ］）はｘ［１］からｘ［ｎ］までの最大値を返す関数である。ＭＩＮ（ｘ［１］．．ｘ［ｎ］）はｘ［１］からｘ［ｎ］までの最小値を返す関数である。ＡＢＳ（ｘ）はｘの絶対値を返す関数である。

In Equation (2), MAX (x [1]... X [n]) is a function that returns the maximum value from x [1] to x [n]. MIN (x [1]... X [n]) is a function that returns a minimum value from x [1] to x [n]. ABS (x) is a function that returns the absolute value of x.

  Step S5: The control unit 8 multiplies the information (BvMean, BvC, BvMax, BvMin, dHE), which is the characteristic of the subject obtained in Step S4, by the weighting factors K1 to K5, respectively, and the luminance value by the following equation (3). Calculate BvAns. Note that the weighting factors K1 to K5 in Expression (3) are optimized according to the selected photometry mode.

ステップＳ６：制御部８は、ステップＳ１の６４個の測光値から最大測光値Ｂｍａｘを検出する。そして制御部８は、最大測光値Ｂｍａｘを得た分割領域の座標［ｍａｘｈ，ｍａｘｖ］を求める。

Step S6: The controller 8 detects the maximum photometric value Bmax from the 64 photometric values in step S1. And the control part 8 calculates | requires the coordinate [maxh, maxv] of the division area which obtained the maximum photometric value Bmax.

  Step S7: The control unit 8 detects the group size MaxAmt of the divided area where the maximum photometric value Bmax is obtained. Specifically, the control unit 8 continuously outputs a photometric value of a certain level or more from the divided area [maxh, maxv] where the maximum photometric value Bmax is obtained (for example, the divided area [maxh, maxv] as a center). The range in which the output photometric value is not less than the intermediate value between the maximum photometric value Bmax and the luminance value BvAns) is detected, and the total number of divided areas included in the range is counted to obtain MaxAmt (see FIG. 5).

  Step S8: The control unit 8 determines that the difference between the maximum photometric value Bmax and the luminance value BvAns is equal to or smaller than a predetermined value (dTh) and the size (MaxAmt) of the divided area where the maximum photometric value Bmax is obtained is a threshold value amth1 (for example, , MaxAmt is about 10) or more. If the above condition is satisfied (YES side), the process proceeds to step S9. If the above condition is not satisfied (NO side), the process proceeds to step S10.

  Step S9: In this case, when the exposure amount is calculated with the brightness value BvAns obtained in step S5, the exposure is underside. Therefore, the control unit 8 changes the luminance value BvAns to a value obtained by subtracting the constant Bsat1 from the maximum photometric value Bmax (BvAns = Bmax−Bsat1), and then proceeds to step S12. Note that if the exposure amount is calculated using the luminance value BvAns changed in step S9, the exposure amount is increased as compared with the case where the exposure amount is calculated using the luminance value before the change.

  Step S10: The control unit 8 has a difference between the maximum photometric value Bmax and the luminance value BvAns larger than a predetermined value (Bsat2), and the divided area [maxh, maxv] is located near the center of the screen (3 <maxh <6, 3 It is determined whether or not <maxv <6) and the size (MaxAmt) of the divided area is larger than the threshold value amt2. If the above condition is satisfied (YES side), the process proceeds to step S11. If the above condition is not satisfied (NO side), the process proceeds to step S12.

  Step S11: In this case, the main subject at the center of the screen has a group of high-luminance portions, and an exposure that does not saturate the high-luminance portions is required. Therefore, the control unit 8 changes the luminance value BvAns to a value obtained by subtracting the constant Bsat2 from the maximum photometric value Bmax (BvAns = Bmax−Bsat2), and then proceeds to step S12. Note that if the exposure amount is calculated using the luminance value BvAns changed in step S11, the exposure amount is reduced as compared with the case where the exposure amount is calculated using the luminance value before the change.

  Step S12: The controller 8 calculates an exposure amount based on the luminance value BvAns, and executes automatic exposure control of the camera based on the exposure amount. Here, when the condition of step S8 is met, the control unit 8 calculates the exposure amount with the brightness value BvAns of step S9. If the condition in step S10 is met, the control unit 8 calculates the exposure amount using the luminance value BvAns in step S11. If neither of the conditions in step S8 and step S10 match, the control unit 8 calculates the exposure amount with the brightness value BvAns in step S5.

Hereinafter, effects of the first embodiment will be described. In the electronic camera of the first embodiment, the luminance value is changed in consideration of the maximum photometric value in the divided area and the size of the group of divided areas from which the maximum photometric value is obtained. Therefore, it is possible to obtain an appropriate exposure reflecting the brightness of the object scene and the size of the high luminance part.
For example, in the first embodiment, in the field where the difference between the maximum photometric value and the luminance value is small, the exposure amount is increased only when the group of divided areas is large to some extent (S8, S9). Under-exposure is suppressed.

Further, in the first embodiment, when the difference between the maximum photometric value and the luminance value is large and the group of divided areas where the maximum photometric value is obtained is located near the center of the screen, the exposure amount is reduced (S10, S11). Therefore, with the electronic camera of the first embodiment, it is possible to obtain an appropriate exposure for the main subject even when, for example, a flower with a shaded background is photographed.
Further, the control unit 8 according to the first embodiment counts the divided areas included in the range in which the photometric value of a certain level or more is continuously output from the divided area of the maximum photometric value Bmax, so that the maximum photometric value is obtained. A group of regions can be detected with relatively high accuracy.

(Description of Second Embodiment)
The second embodiment is a modified example related to the detection of a group of divided areas (corresponding to S7 in FIG. 4) of the first embodiment. In the description of the second embodiment, only differences from the first embodiment will be described, and descriptions of common parts will be omitted.
First, the control unit 8 according to the second embodiment determines the length of a range in which a photometric value that is equal to or greater than a certain value is continuously output for the divided area [maxh, maxv] in which the maximum photometric value Bmax is obtained. , Maxv] is obtained as a line segment in two vertical and horizontal directions. Specifically, as shown in FIGS. 6 and 7, the control unit 8 has a range that is equal to or greater than an intermediate value between the maximum photometric value Bmax and the luminance value BvAns in the horizontal and vertical directions of the divided area [maxh, maxv]. The lengths maxdh and maxdv are obtained respectively.

And the control part 8 calculates the magnitude | size (MaxAmt) of the division | segmentation area | region where the maximum photometric value Bmax is obtained by the following formula | equation (4).
MaxAmt = (maxdh × maxdv) / 2 (4)
In the second embodiment, the control unit 8 approximately calculates the size of a group of divided areas where the maximum photometric value is obtained based on maxh and maxv. Therefore, although the accuracy is lower than that in the first embodiment, it is possible to suppress the calculation amount of the divided areas.

(Correspondence between Claims and Embodiments)
Here, the correspondence between the claims and the embodiment is shown. Note that the correspondence relationships shown below are interpretations shown for reference only, and do not limit the technical scope of the present invention.
1st Embodiment respond | corresponds to the photometry apparatus of the camera of Claims 1-4, and 2nd Embodiment respond | corresponds to the photometry apparatus of the camera of Claim 5. The divided photometry element 7 corresponds to the “photometry unit”. The control unit 8 corresponds to the “first calculation unit”, “maximum photometric value detection unit”, “high luminance part detection unit”, and “second calculation unit”.

(Supplementary items of the embodiment)
As mentioned above, although this invention has been demonstrated by said embodiment, the technical scope of this invention is not limited to the said embodiment.
(1) For example, the number of divided areas of the divided photometric element is not limited to 64. Further, the information that is characteristic of the subject is not limited to the above embodiment, and can be appropriately changed according to the performance required for the photometric device.

(2) In step S10 of the first embodiment, the luminance value is changed when the group of divided areas where the maximum photometric value is obtained is located near the center of the screen. In the present invention, the group of divided areas is the center of the screen. Even when it is located outside the vicinity, the exposure value may be decreased by changing the luminance value.
(3) In the detection of a group of divided areas in the above embodiment, an intermediate value between the maximum photometric value Bmax and the luminance value BvAns is exemplified as a threshold value, but this threshold value can be changed as appropriate. For example, the half value of the maximum photometric value Bmax may be set as the threshold value.

  (4) In the detection of a group of divided areas according to the second embodiment, the length of a range in which a photometric value that is a certain level or more is continuously output is obtained in the horizontal and vertical directions with the divided area where the maximum photometric value is obtained as an intersection. However, this is only an example. For example, the lengths of the line segments are calculated in four directions of the horizontal direction, the vertical direction, and the 45-degree oblique direction with the divided area where the maximum photometric value is obtained as an intersection, and the group of divided areas is calculated as an octagon. It may be. In this case, the accuracy of approximation is improved as compared with the case where the length of the line segment is obtained in the horizontal direction and the vertical direction. Of course, the accuracy of approximation can be further improved by further increasing the number of line segments for which the length is obtained.

  (5) In the above embodiment, the camera photometry device of the present invention is applied to a single-lens reflex type electronic camera. However, the present invention is applicable to a single-lens reflex type silver salt camera or a compact type electronic camera. It can also be applied to a photometric device.

  The present invention can be applied, for example, to a single-lens reflex type electronic camera and a silver salt camera, or a split photometry device of a compact type electronic camera.

The figure which shows the structure of the electronic camera of 1st Embodiment. The figure which shows the division area of a division photometry element The figure which shows grouping of the division area of a division | segmentation photometry element Flow chart showing the operation of exposure calculation of the first embodiment Schematic diagram regarding detection of a group of divided areas according to the first embodiment Schematic diagram regarding detection of a group of divided areas according to the second embodiment The figure regarding the detection of the length of the line segment in 2nd Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera body 2a Shooting lens 5 Image pick-up element 6 Re-imaging lens for photometry 7 Division | segmentation photometry element 8 Control part

Claims (6)

A photometry unit that divides the object scene into a plurality of divided areas and detects a photometric value for each of the plurality of divided areas ;
A first operation unit, wherein the grouping a plurality of divided regions into a plurality of groups, calculates the luminance value of the object scene based on the photometric value of the divided regions included in the group,
A maximum photometric value detection unit that detects a maximum photometric value that is the maximum photometric value from the plurality of divided regions;
A high-intensity range detection unit that detects a size of a range in which the photometric value equal to or greater than a threshold value is detected continuously from the divided area in which the maximum photometric value is detected ;
A second calculation unit that changes the luminance value using a size of the range detected by the high luminance range detection unit and a value corresponding to a difference between the maximum photometric value and the luminance value ;
A camera photometric device characterized by comprising: A camera photometry device according to claim 1,
The second calculation unit compares the size of the range detected by the high luminance range detection unit with a predetermined first threshold, and a value corresponding to the difference between the maximum photometric value and the luminance value compared to the predetermined second threshold, the camera photometry device and changes the luminance value so that the amount of exposure increases. A camera photometric device according to claim 1 or claim 2,
The second calculation unit is configured such that a difference between the maximum photometric value and the luminance value is larger than a predetermined value, and the divided region where the maximum photometric value is detected is located near the center of the screen, and the high luminance range detection unit detected when the size of the range is a predetermined threshold value or more, the camera photometry device and changes the luminance value so that the amount of exposure is reduced. A camera photometric device according to any one of claims 1 to 3,
The photometric device of a camera, wherein the high-luminance range detection unit detects the size of the range by counting the total number of the divided areas in which the photometric value equal to or greater than the threshold is detected . A camera photometric device according to any one of claims 1 to 3,
The high luminance-range detector in the camera's metering device, characterized in that for calculating the size of the range using the plurality of line segments to the intersection of the division area where the maximum photometry value is obtained.   A camera comprising the photometric device according to any one of claims 1 to 5.

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