JPH05297434A - Photometry method for camera - Google Patents

Abstract

PURPOSE:To attain center-weighted measuring and divided brightness measuring even in a camera not adopting a TTL photometry system by always and accurately making the center of a finder coincident with the center of a photometric value extracting area. CONSTITUTION:An image area sensor 31 composed of a large number of photometry elements is disposed on a photometry part 26. A field is projected on the area sensor 31. The distance of an object is detected and a parallax is obtained by a parallax determining part 23, based on the detected distance. The photometric value extracting area is moved in the area of the area sensor 31, according to the parallax, to calculate a photometric value, based on the brightness data of the photometry elements of the photometric value extracting area, by a photometric value extracting part 25, an exposure is controlled based on the photometric value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometry method for a camera, and more particularly to a photometry method for a camera such as a compact camera which does not perform TTL photometry.

[0002]

2. Description of the Related Art As a photometric method for a single-lens reflex camera, a multi-divisional photometric method is widely used in which an object field is divided into a plurality of areas to perform TTL photometry. On the other hand, in an external photometry method other than TTL photometry, the optical axis of photography and the optical axis of photometry are different, and it is difficult to perform photometry by matching with the photography area.

[0003]

For this reason, there is a deviation between the scene scene to be photographed and the scene scene to be metered, and even if the light is divided and metered, it is possible to obtain a specific position in the scene. ,
For example, since the main part is shifted between the two scenes, the subject brightness of the main part cannot be accurately measured. Therefore, a compact camera using such an external photometry system does not perform multi-division photometry with good exposure accuracy.
Further, even in a compact camera having a zoom function, the angle of view changes due to zooming and the photometric area is not fixed, and there is the same problem as described above.

The present invention is intended to solve the above problems, and provides a photometric method for a camera, such as a compact camera, which is not a TTL photometric system, which improves photometric accuracy and enables high-precision exposure control. The purpose is to do.

[0005]

In order to achieve the above-mentioned object, the present invention provides an area sensor comprising a large number of photometric elements in a photometric section, projects an object field onto the area sensor, The photometric area for photometry is corrected according to the subject distance or the photographing magnification.

[0006]

FIG. 2 shows a compact camera embodying the present invention. The light projecting unit 11 includes a light source unit that generates spot-shaped infrared light. When the release button 12 is half-pressed, the controller 13 controls the light projecting unit 11 to project the irradiation light 16 toward a position corresponding to the target mark of the shooting scene 10.

The reflected light 18 reflected by the main subject 17 by the irradiation light 16 passes through a lens 19 and enters an image area sensor 20 which is an incident position detecting means. The time series signal from the image area sensor 20 is sent to the subject distance detection circuit 21.

The subject distance detection circuit 21 obtains the position where the reflected light 18 is incident from the time-series signal of the image area sensor 20, detects the distance to the main subject 17 based on this incident position, and outputs the signal of this subject distance. (Hereinafter referred to as distance measurement data) is sent to the lens setting unit 22 and the parallax amount determination unit 23. The lens setting unit 22 controls the focus of the taking lens 27 based on the distance measurement data.

The parallax amount determination unit 23 determines the parallax amount of the photometric system. As shown in FIG. 3, the parallax amount (e) is the subject distance (a), the focal length of the photometric lens (f), and the difference (A) between the optical axis of the finder 25 and the optical axis of the photometric unit 26. Can be determined by That is, as shown in FIG. 3, among these e, A, a, and b, the relationship of e: b = A: a is established, so that e = (b / a) A. When this is transformed at the focal length (f) of the photometric lens, e = (f / (af)) A. Further, the viewfinder 2 is calculated by the ratio (α ′ / α) between the view angle (α) of the viewfinder 25 and the view angle (α ′) of the photometric screen.
The parallax amount e ′ = e (α ′ / α) of the photometric unit 26 for 5 is obtained. The relationship between the photometric system parallax amount e ′ and the distance measurement data is stored in advance in a built-in memory,
When the distance measurement data is input, the photometric system parallax amount (e ') corresponding to this is obtained. Instead of storing the above relationship in the memory in advance, the photometer parallax amount e ′ may be sequentially calculated from the subject distance.

As shown in FIG. 2, the photometric section 26 is composed of a lens 30 and an image area sensor 31 composed of a CCD (charge coupled device). Luminance data from each photometric element of the image area sensor 31 is converted into a digital signal by the A / D converter 33 and sent to the photometric value extraction unit 25. As shown in FIG. 4, the photometric value extraction unit 25 moves the photometric value extraction area A2 in the parallax correction direction in the entire area A1 of the image area sensor 31 by the parallax amount (e ′), and Luminance data of each photometric element in the extraction area A2 is extracted. Photometric value extraction area A
2 is determined according to the shooting screen, and in this embodiment, the photometric element 30 × 4 of the image area sensor 31 is selected.
It is composed of 5 sets. Image area sensor 31
Is composed of, for example, photometric elements arranged in a 200 × 200 matrix. In this embodiment, since the viewfinder 25 and the photometric unit 26 are arranged in the horizontal direction of the camera, the parallax correction direction is the horizontal direction, which is the same as the photometric unit of the camera and the viewfinder. It changes depending on the positional relationship of.

The photometric value extraction unit 25 further determines the photometric value B by the weighted average of the brightness data in each photometric element as shown in Expression 1 in order to perform exposure control with emphasis on the central portion based on the extracted brightness data. calculate.

[0012]

[Number 1] _{B = ΣΣ (K ij · S} ij) / ΣΣK ij However, K _ij is a weighting factor, with nearly become larger value in the center C2.

The photometric value data B from the photometric value extracting section 25 is sent to the exposure control section 38. The exposure control unit 38 controls the exposure amount by program control based on the photometric value B. A film sensitivity signal is input to the exposure control unit 38, and a light value (LV) is calculated from this and a photometric value B, and the diaphragm drive unit 40 and the shutter drive unit 41 are program-controlled. Further, as is well known, the exposure control unit 38 includes a subject brightness determination circuit, and automatically emits a flash device (not shown) in synchronization with the shutter mechanism 42 when the subject brightness in the main subject area is low.

A known diaphragm mechanism 44 and shutter mechanism 42 are arranged behind the taking lens 27. Each of these mechanisms 42 and 44 operates when the release button 12 is pushed further from the half-pressed state, and exposes the negative film 45.

Next, the operation of this embodiment will be described. When the camera is held and the release button 12 is pressed halfway down, the controller 13 projects the irradiation light 16 toward the main subject 17 located at the target mark of the shooting scene 10, and the reflected light 18 allows the main subject 17 to reach the main subject 17. Detect the distance. Further, the photometric unit 26 digitizes the brightness data from the image area sensor 31 via the A / D converter 33 and sends it to the photometric value extraction unit 25.

The distance measurement data is sent to the parallax amount determination unit 23, where the parallax amount (e ') of the photometric system is determined from the distance measurement data. Based on the parallax amount (e ′) of the photometric system, the photometric value extraction unit 25 determines the photometric value extraction area A within the entire area A1 of the image area sensor as shown in FIG.
2 is moved, and based on the brightness data of each photometric element in this area A2, the photometric value B which emphasizes the main part by the mathematical formula 1
To calculate.

The exposure control section 38 calculates a light value (LV) based on the photometric value B and the film sensitivity, and program-controls the diaphragm drive section 40 and the shutter drive section 41 based on the calculated light value (LV). Then, when the release button 12 is further pressed from the half-pressed state, the diaphragm drive unit 40 and the shutter drive unit 41.
Is operated to photograph the main subject 17 with an optimum exposure amount. FIG. 1 shows a program of the above procedure.

In the above embodiment, the center-weighted photometry method has been described, but in addition to this, exposure control may be performed by multi-division photometry. In this case, as shown in FIG.
The photometric value extraction area A2 is divided into 25 subareas SA1 to SA25 in a matrix of 5 × 5, and one subarea is composed of 36 × 24 photometric elements. And 2
Photometric value Sn (n = n = 5) of five sub-areas SA1 to SA25
1 to 25) are combined by Equation 2, and the photometric value B
Exposure control is performed for

[0019]

[Equation 2] Sn = ΣΣS _ij (i = x + 1 to x + 36, j = y + 1 to y + 24)

[0020]

[Equation 3] B = (ΣKn.Sn (n = 1 to 25) + K26.Sma
x + K27.Smin) /. SIGMA.Kn (n = 1 to 25), where: Kn: Weighting coefficient predetermined by subject scene Smax: Central area (S7, S8, S9, S12, S1)
3, S14, S17, S18, S19) maximum value Smin: central area (S7, S8, S9, S12, S1)
3, S14, S17, S18, S19) The maximum value of Sn is converted to low brightness in the case of direct sunlight, reflected light, and bright sky brightness, as shown in FIG. The subsequent luminance data S'n is used.

Different weighting factors Kn are used in the normal light scene and the backlight scene. For example, as shown in Formula 4, the average value of Smin and Smax, and S1 to S2
When the average value of Smin and Smax is equal to or more than the average value of S1 to S25, it is determined to be a normal light scene.

[0022]

## EQU00004 ## (Smin + Smax) /2.gtoreq..SIGMA.Sn (n = 1 to 25) / 25

In this case, the central area SA7 to SA
9, SA12 to SA14, SA17 to SA19, the maximum value Smax is weighted to the maximum with a weighting factor of 3.0, and then the respective photometric values S7 to S9, S12 to S14, S in the central area are weighted.
17 to S19 and the minimum value Smin of the central area are weighted by the weighting coefficient 0.4, and the photometric values S1 to S6, S10, S11, S15, S16 and S2 of the other peripheral areas are weighted.
0 to S25 are weighted with a weighting factor of 0.1. As a result, in a normal light scene, the main subject is less affected by the background, and the main subject can be photographed with an appropriate exposure amount.

Further, as shown in Equation 5, Smin and Sma
Comparing the average value of x and the average value of S1 to S25,
When the average value of Smin and Smax is less than the average value of S1 to S25, it is determined to be a backlight scene.

[0025]

## EQU00005 ## (Smin + Smax) / 2 <.SIGMA.Sn (n = 1 to 25) / 25

In this case, the minimum value S in the central area
min is maximally weighted with a weighting factor of 3.0, and then each photometric value S7 to S9, S12 to S14, S17 in the central area is
To S19 and the maximum value Smax of the central area are weighted with a weighting coefficient of 0.2, and the photometric values S1 to S6, S10, S11, S15, S16 and S20 of the other peripheral areas are weighted.
~ S25 is weighted with a weighting factor of 0.1. As a result, in a backlight scene, the main subject is less affected by the background, and the main subject can be photographed with an appropriate exposure amount. Therefore, in a backlit scene, it is possible to prevent the main subject from having a high density when the main subject is usually underexposed due to the influence of the background and becomes a print photograph.

Further, according to the present invention, in a camera in which the optical axis of the taking lens and the optical axis of the photometric lens are different from each other, the photometric value extraction area may be corrected by the zoom magnification. In this case, the angle of view changes depending on the focal length of the lens used, such as a zoom lens or a wide-angle lens, so the size of the photometric value extraction area on the image area sensor is changed according to the angle of view created by the taking lens. .. Therefore, in the case of a long focus, the angle of view becomes small, and a part of the field projected onto the image area sensor is metered as a photometric value extraction area. In this case, the parallax is corrected at the same time as described above. Further, each of the plurality of sub-areas of the photometric value extraction area is also changed in proportion to the area of the photometric value extraction area. For example, in the case of 3 × zoom, the photometric value extraction area is set to about 1/9 in the second embodiment. Naturally, the sub area is also reduced to 1/9.

In the above embodiment, the composition is usually determined through the viewfinder, so parallax caused by the difference between the optical axis of the viewfinder and the optical axis of the photometric lens is corrected. The same can be applied to a camera in which there is a difference between the optical axis of the optical axis and the optical axis of the photometric lens. Further, as a matter of course, the present invention may be applied to a camera in which the optical axes of the taking lens and the photometric lens coincide with each other, and the optical axis of the finder and the optical axis of the photometric lens have a gap.

In each of the above embodiments, the number of divisions of the photometric value extraction area, the division method, and the method of obtaining the parallax amount are not limited to the description of the present invention. The present invention also includes changing the photometric area and the division of the photometric area around the focus point. That is, the number of divisions and the division method of the photometric area may be changed according to the subject distance and the photographing magnification. For example, the distance may be divided into two so that downward weighted photometry is performed at a long distance. Further, the positions of the photometric value extraction area and the sub area on the image area sensor may be calculated each time for the object distance and the photographing magnification, or may be stored in the memory in advance.

Further, in the above embodiment, each photometric element is extracted according to the parallax amount after the photometry and the photometric value B is calculated based on this, but in addition to this, it is used on the image area sensor according to the parallax amount. A photometric element may be selected and the photometric value may be calculated from the brightness data output from the selected photometric element.

Further, in the above embodiment, the photometric value extraction unit extracts the luminance data of the necessary area directly from the image area sensor, but in addition to this, the luminance data of each pixel of the image area sensor is stored in the photometric value memory. It may be stored and the photometric value may be extracted from this in accordance with the parallax amount.

[0032]

As described above, according to the present invention,
Since the metering area is corrected according to the subject distance and shooting magnification, the center of the viewfinder and the center of the metering area always match exactly, and even if the camera does not use the TTL metering method, the center-weighted Enables metering and split metering. Therefore, even in an external photometric camera such as a compact camera, it is possible to realize high-precision exposure control at a small size and at low cost.

[Brief description of drawings]

FIG. 1 is a flowchart showing a photometric method of a camera of the present invention.

FIG. 2 is a schematic diagram showing a camera of the present invention.

FIG. 3 is an explanatory diagram for calculating a parallax amount of a photometric system.

FIG. 4 is an explanatory diagram showing a state in which a photometric value extraction area is moved according to a parallax amount of the photometric system.

FIG. 5 is an explanatory diagram showing sub-areas of a photometric value extraction area when a divided photometric method is adopted.

FIG. 6 is a graph for converting high-brightness data into low-brightness data by the division photometry method.

[Explanation of sign]

 10 Shooting Scene 11 Light Emitting Unit 17 Main Subject 23 Parallax Amount Calculation Unit 25 Finder 26 Photometric Unit 31 Image Area Sensor e'Photometric System Parallax Amount A2 Photometric Value Extraction Area

Claims (1)

[Claims] 1. In a camera having a difference between the central axis of the finder and the optical axis of the photometric lens, an area sensor including a large number of photometric elements is arranged in the photometric section, and a field is projected onto the area sensor. A photometric method for a camera, characterized in that a photometric area for photometry of an object field is corrected according to a subject distance or a photographing magnification.