JP2982229B2 - High brightness processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric circuit of a camera, and more particularly to a high-brightness processing circuit when a high-brightness portion exists in an object scene.

2. Description of the Related Art Conventionally, in a photometry circuit that arranges a plurality of light receiving elements on a light receiving surface that receives object scene light and measures the luminance value, a photometric circuit is used when a high luminance portion exists in the object scene light. Several methods have been used for processing the photometric output output from the element.

Japanese Patent Publication No. 60-11475 (hereinafter referred to as a first conventional example) includes a plurality of photometric elements, and a fixed reference value for distinguishing between high luminance and low luminance. An invention is described in which when the output of an element exceeds or falls below its reference value and it is determined that the luminance is high or low, the output is excluded and the exposure calculation is performed.

Also, Japanese Patent Application Laid-Open No. 62-198721 (hereinafter referred to as a second conventional example)
In the invention, a plurality of photometric elements are similarly provided, and when an output from any one of the elements shows high luminance, a correction is made to a calculated value calculated from each photometric element output in accordance with a photometric output level. Are listed.

Problems to be Solved by the Invention In the first conventional example among the above-described devices, exposure calculation is performed excluding high-luminance and low-luminance photometric outputs. In such a device, however, many elements are used. When a high-luminance output is obtained, the actual photometric area becomes small and the exposure becomes unstable.

Further, in the second conventional example, correction according to the photometric output level is applied to the calculated value. However, since the calculated value is corrected, it is difficult to cope with small fluctuations in the output of the photometric element.

The present invention has been made in view of the above problems, and has as its object to provide a high-brightness processing circuit that corrects a photometric element output so that an appropriate exposure can always be obtained regardless of the state of subject field light. .

Means for Solving the Problem In order to solve the above problems, in the present invention, a plurality of photometric elements disposed on a light receiving surface for receiving light from a subject, and each photometric output BV of the photometric element are predetermined. a determination section for determining whether is greater than the value BV _0, the formula BV '= α × (BV- BV 0) to the photometric output is determined larger than the predetermined value by the determination unit + BV ₀ in the above equation alpha is A value such as a predetermined constant value is weighted for correction, and a value BV 'reduced from the value BV
A weighting unit that outputs a weighted value of the photometric output of the photometric element whose output is determined to be greater than a predetermined value, and a photometric output BV of the photometric element whose output is not determined to be equal to or greater than the predetermined value. And a calculating means for performing a photometric calculation from the above.

According to the configuration described above, if a high-luminance part exists in the object scene, the photometric element output of that part is not used for exposure calculation as it is, but after a certain weight is added. Used for exposure calculation.

Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is a compact camera configured by using the present invention, and has an autofocus function based on distance measurement data and an automatic exposure function based on photometry data.

FIG. 1 is an explanatory diagram showing an overall operation flow of an embodiment of the present invention. In the photometric data input routine 1, the photometric element outputs output from the plurality of photometric elements provided at the center and outside of the photographing area are weighted when they are equal to or greater than a predetermined value in the high brightness processing routine 2. The photometric element output is output as a photometric element output luminance value. In the exposure control value calculation routine 3, the exposure control luminance is calculated from the main subject distance, the photographing lens focal length, and the output luminance value of the photometric element with the above-mentioned weighting amount changed. In the flash emission determination routine 4, a calculation is performed from the above-described exposure control luminance and the camera shake limit value calculated from the photographing lens focal length and the main subject distance, and when it is determined that the luminance is low or backlight, the flash emission is performed. decide.

On the other hand, the distance measurement data input from the distance measurement data input routine 5 is used to calculate the main subject image magnification in the image magnification calculation routine 6, and the result is used in the FM correction amount routine 7; When the magnification is large, the main subject is prevented from being excessively emphasized by the flash light, thereby preventing the finished image from having a stylized finish. Next, in the flash emission timing calculation routine 8, in order to obtain a sufficient exposure amount,
The flash emission timing is calculated.

Further, in the catchlight mode routine 9, a flash emission is forcibly performed on a main subject such as a person when a catchlight effect is desired. However, even in this case, if it is determined that the effect of the catchlight is weak based on the image magnification, the warning LED blinks and no light is emitted.

The flash exposure control routine 10 determines the flash emission in the flash emission determination routine 4 or based on the flash timing from the flash emission timing calculation routine 8 when the catch light mode is on and its effect can be expected. And emit light. Further, the non-flash exposure control routine 11 performs the flash emission without performing the flash when the flash emission is not determined in the flash emission determination routine 4 or when the effect is not expected even if the catch light mode is on. Perform control.

Next, the configuration of an embodiment of a camera to which the present invention is applied will be described with reference to FIG. FIG. 2 is a schematic diagram of the configuration of the present embodiment. The photometric optical system 101 performs photometry in a shooting area. There, light passing through the photometric lens 102 is applied to the photometric elements 103 and 10 corresponding to the central portion and the outer portion of the photographing area, respectively.
After the photometry is performed in the photometry circuit 105 and processed in the photometry circuit 105, the output is supplied to a microcomputer 115 for camera control.
Is input to

On the other hand, in the photographing optical system 106, the field light passes through the photographing lens 107 and the aperture opening 108, and is guided to the distance measuring circuit 110 by the AF mirror 109 to detect the defocus amount with respect to the in-focus position. Is input to the microcomputer 115 for camera control. 111 is a light shielding film, and 112 is a film.

The photometry value and the distance measurement value output from the photometry circuit 105 and the distance measurement circuit 110 are microcomputers for camera control.
At 115, it is used to control the control circuit for flash firing, exposure, and lens. Exposure control circuit 11
3 controls the exposure by driving the aperture blades 108, the lens control circuit 114 controls the driving of the photographing lens 107 such as zooming and focusing, changes the focal length f due to zooming, focuses on the main subject by focusing. The distance DV is output to the camera control microcomputer 115. Reference numeral 116 denotes a flash body, and a flash emission control circuit 117 controls flash emission timing.

A catch light switch 121 performs exposure control in a catch light mode when the catch light switch is turned on. Reference numeral 122 denotes an image magnification changeover switch for switching the limit image magnification for performing flash emission according to the print size. The viewfinder optical system 118 includes a viewfinder lens 119 and a warning LED1.
If the image magnification is such that the catchlight effect does not occur when the catchlight switch is turned on, the warning L is controlled by the camera control microcomputer 115.
The ED flashes to notify affected people.

Next, for each routine shown in FIG.
Each will be described. FIG. 3 shows a high-brightness processing routine. Element outputs BVi from a plurality of photometric elements provided at the central part and the outer part of the affected area input in the photometric data input routine 1 shown in FIG. Enter Here, when i = 1, it is the output of the central element, i
= 2 is the output of the outer element. In # 2, the input element output is weighted, and the element output calculation memory ▲
BV ^m _i ▼ to. In # 3, memory for element output calculation ▲ BV
Compare ^m _i ▼ with the element output BVi. This is because the exposure calculation using the actually weighted values is based on the element output.
This is because it is only when BVi is equal to or more than a predetermined value (28/3 Bv in the formula of # 2). Here, ▲ BV ^m _i ▼ be of greater BVi (weighted value is greater than the original output value) is that the lower luminance than the predetermined value, # element output calculation subjected to weighting in 2 since memory ▲ BV ^m _i ▼ is not necessary, the element output BVi the element output calculation memory ▲ BV ^m _i ▼ at # 4. On the other hand, in the # 3 ▲ BV ^m _i ▼ is BVi
Less than (the weighted value is smaller than the original output value) means higher brightness than the predetermined value,
Weighting the outputs as an element output calculation memory ▲ BV ^m _i ▼ subjected. # Outputs the 5 In ▲ BV ^m _i ▼ as photometric element output luminance values BVi.

FIG. 4 shows an exposure control value calculation routine. In step # 6, the main subject distance DV, the photographic lens focal length f, and the film sensitivity SV are input. Here, the main subject distance DV and the film sensitivity SV are APEX values. In step # 7, the exposure control brightness BV is calculated from the element output BVi obtained by changing the main subject distance DV, the photographing lens focal length f, and the weighting amount. In # 8, an exposure control value EV is calculated from the exposure control luminance BV and the film sensitivity SV.

FIG. 5 shows a flash emission determination routine. In step # 9, the photographing lens focal length f is input, and in step # 10, the main subject distance DV is such that the non-defective rate is 90% or more when the main subject distance DV and the shutter speed are hand-held at the reciprocal 1 / f of the focal length f. Enter ₀ . Obtaining a value TV ₀ determined from the correction of the focal length f and the main object distance DV in # 11 by using this.
In # 12, obtains the aperture value AV ₀ corresponding to TV ₀ from the program diagram is built using the values TV ₀ described above. In step # 13, the camera shake limit brightness EV ₀ is calculated from the above-mentioned AV ₀ , TV ₀ , DV ₀ , DV, and whether the camera shake limit brightness ED ₀ is larger than the exposure control value EV at that time or whether the camera is in a backlight state. to decide. When the exposure control value EV is lower than the limit brightness EV ₀ shake, or subjected to flash in # 14 when a backlight, the process proceeds to # 15 without performing the flash when it is not.

The non-defective rate here means the probability of obtaining a photograph that can be recognized as having no blurring when photographed under a predetermined condition. Specifically, a large number of photographings are experimentally performed under a predetermined condition. It is determined statistically by calculating the ratio of the obtained photographs that can be recognized as having no blurring. For example, FIG. 13 shows one example, in which the horizontal axis indicates the amount of image shift, and the vertical axis indicates the number of obtained photographs.
According to this example, when a point image at the distance D _VS is hand-held and photographed at the focal length f _S and the shutter speed T _VS , the image shift amount is smaller than the amount that can be recognized as not blurring (that is, the blur is smaller). No pictures) are obtained for the number of regions I. The ratio of the number of samples in the region I to the total number of samples is defined as a non-defective rate. As the focal length becomes shorter and the shutter speed becomes faster, the distribution in the figure moves to the left, and the yield rate improves.

FIG. 6 shows an image magnification calculation routine. In step # 16, the main subject distance DV and the photographic lens focal length f are input from the distance measurement data input routine 5. In # 17, the main subject distance D is obtained from DV. This D is not an APEX value but a true main subject distance. In step # 18, the image magnification is calculated from D and f described above.

FIG. 7 is a flashmatic correction amount calculation routine. In # 19, it is determined whether or not the subject is backlit. Otherwise, the flashmatic correction amount ΔEV is set to 0 in # 20.
Conversely, when it is determined that the subject is backlit, the flash light amount is set to under in accordance with the image magnification. By doing so, it is possible to prevent the main subject from being excessively emphasized by the flash light when the image magnification is large, thereby preventing the picture from having a striking finish. The correction amount △ EV is determined according to the image magnification, and the graph shown in # 21 shows the reciprocal 1 / β of the multiplication factor β on the horizontal axis and the flashmatic correction amount △ EV on the vertical axis. Decided. As the reciprocal of the image magnification β becomes smaller than 40 (as the image magnification becomes larger), the correction amount increases. By doing so, the flash light is corrected slightly under, so that an appropriate contrast of the subject can be obtained. That is, the flash light amount is corrected only when it is determined that the subject is backlit. In other cases where flash light emission is performed, the correction amount ΔEV is set to 0. This includes scenes other than backlight and below the camera shake limit luminance, or during forced light emission in the catchlight mode. In the former, exposure control is performed below the camera shake limit brightness, so natural light will be under, and the photographer expects a catchlight effect using flash light in the latter, using a flash to compensate for the lack, and the latter in the latter. , The correction amount ΔEV is set to 0.

FIG. 8 shows a flash emission timing calculation routine. At # 22, the flash guide number amount IV, the film sensitivity SV, and the main subject distance DV are input as APEX values, respectively, and at # 23, the flash emission timing AVd, that is, the aperture value for flash emission, is obtained.

FIG. 9 shows a non-light emission exposure control routine. In # 24, it is determined that the flash is not fired in # 13 of the flash emission determination routine, and it is determined that the catchlight effect cannot be obtained from the image magnification even if the catchlight mode is off or on. In this case, shooting without flash emission is performed. That is, using the exposure control value EV obtained in # 8, the aperture value AV and the exposure time TV corresponding to EV are obtained from the program diagram.

FIG. 10 is a light emission exposure control routine. In # 26 #
A luminance EV ₀ of camera shake limit determined by 13 than the exposure control value EV, when the exposure control value EV is equal to or less than the limit value EV ₀ shake is an exposure control value EV limits EV ₀ shake at # 27. Otherwise, the exposure control value EV is used as it is.
In step # 28, the aperture value AV and the exposure time TV are obtained from the built-in program chart using the exposure control value EV determined in this way. In step # 29, the aperture value AV is compared with the flash emission aperture value AVd. When AVd is larger, it is within the range where the flash light reaches the main subject. The flash emission aperture value AVd obtained in # 23 and the aperture value AV obtained in # 28,
Exposure time Proceed to # 30 to perform TV exposure. When the AV is larger, the main subject is farther than the flash light reaches. At this time, if you open the aperture further,
At the time of backlight, the image is overexposed due to natural light components, and at the time of low luminance, it becomes a camera shake photograph. Therefore, in step # 31, the aperture value AV is set to the aperture value at the time of flash emission, and when the aperture is set to AV, that is, when the aperture is opened most, the flash is emitted and the correction by the flash light component is performed.

FIG. 11 shows a catch light mode interruption routine. # 32 is the catch light switch 21 in FIG. In # 33, it is determined whether or not the catchlight switch 21 is on. If not, the process proceeds to # 34 and a return is performed, and the same determination is repeated. If it is on, in step # 35, the image magnification β obtained in step # 18 and the flash emission limit magnification βmin capable of obtaining the catch light effect determined as shown in FIG. 12 are input. In # 36, the above β and βmin are compared, and when β is small, that is, when the image magnification is such that it is difficult to obtain a catchlight effect by emitting a flash, # 37
At the same time, the warning LED blinks and the process proceeds to the non-light emission exposure control routine shown in FIG. When β is large, that is, when the catchlight effect can be obtained by emitting the flash, the process proceeds to the exposure control routine for light emission shown in FIG.

FIG. 12 is a diagram showing a flash emission limit image magnification,
At each print size, the reciprocal of the limit value of the image magnification at which the catchlight effect can be obtained is shown.

Effects According to the present invention, it is possible to prevent a main subject such as a person from being underexposed due to the presence of a high-luminance portion in the scene. In addition, since the element output of the high-brightness portion is not ignored, even if the main subject shows high brightness, the main subject is overexposed due to over-underexposure control. Can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a flow of overall operation of exposure control in an embodiment including the present invention, FIG. 2 is a schematic diagram of a camera configuration of the present embodiment, and FIGS. FIG. 3 is a diagram showing a flow of each part of the whole routine shown in FIG. 1, FIG. 3 is a diagram showing a high brightness processing routine, FIG. 4 is a diagram showing an exposure calculation value calculation routine, and FIG. FIG. 6 is a diagram showing a determination routine, FIG. 6 is a diagram showing an image magnification calculation routine, FIG. 7 is a diagram showing a flashmatic correction amount calculation routine, FIG. 8 is a diagram showing a flash issuance timing calculation routine, and FIG. FIG. 10 shows a light emission exposure control routine, FIG. 10 shows a light emission exposure control routine, FIG. 11 shows a catch light mode interrupt routine, FIG.
FIG. 13 is a diagram showing a flash emission limit image magnification, and FIG. 13 is a diagram for explaining a non-defective product ratio. 103, 104 photometric element 105 discriminator 115 weighting unit

──────────────────────────────────────────────────の Continuation of the front page Examiner Koji Kashiwazaki (56) References JP-A-63-279123 (JP, A) JP-A 64-105222 (JP, A) JP-A-2-87127 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) G03B 7/28

Claims (1)

(57) [Claims] And 1. A plurality of photometric elements arranged on the light receiving surface for receiving light from an object, a determining section for each of the photometry output BV of the photometric device to determine whether it is larger than the predetermined value BV _0, the The photometric output determined to be greater than the predetermined value by the discriminating unit is weighted by a formula BV '= α × (BV−BV ₀ ) + BV _{0 where} α is a predetermined fixed value for correction, and A weighting unit that outputs a value BV ′ smaller than BV, a value BV ′ obtained by weighting the photometric output of the photometric element whose output is determined to be greater than a predetermined value, and that output is determined to be equal to or greater than a predetermined value. And a calculating means for performing a photometric operation from the photometric output BV of the photometric element that did not exist.