JP2803168B2 - Camera exposure calculation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly, to an exposure calculation device of a camera of a divided photometry system.

[Prior Art] Conventionally this type of device, five as shown in Figure 6 screen (i.e. scene) central photometric region C ₁ and the four peripheral portions metering area C ₂ -C ₅ The photometry was performed by dividing the photometry area into the photometry areas. When the split photometry mode is selected by an external switch or the like, the output from the five photometry areas is performed.
Number of calculating an exposure value using the luminance information, also when the center-weighted metering mode is selected, were calculated the exposure value by using the luminance information output from the central portion photometric region C _1.

[Problems to be Solved by the Invention] In recent years, cameras with a built-in autofocus mechanism have become mainstream, and with this, it has become easier for the cameras to identify main subjects. Therefore, according to the distance measurement frame provided in the center of the screen, the vicinity (for example, 24 _mm ×
Obtaining photometric information of a spot of φ3 on a 35 _mm screen has become very important in obtaining an appropriate exposure value.

However, the photometry in such a narrow area originally has a small absolute light quantity as shown in FIG. 5, so that the photometry low luminance limit value becomes a high value (for example, BV-1 with a 50 _mm F1.4 lens). I will. With zoom lenses, which are becoming mainstream in recent years, the aperture value is about F4, so this value increases further and the BV
It will be about 2. In the center-weighted metering, approximately 12 mm (Fig. 6, C1 area) of the screen is measured with emphasis.
BV-5 (50 _mm F1.4) to the extent want to allow photometry,
Since the central φ3 part of the φ12 circle can only measure light up to BV-1, the spot area A1 and its peripheral area as shown in FIG.
In the case where the element is formed by being divided into A2 and A2, the entire photometric range eventually reaches BV-1 (50 _mm F1.4) (see FIG. 5).

The present invention has been made in view of such a problem, and even when a small area spot portion is provided in an area where centrally-weighted photometry is to be mainly performed, the BV-5 (50 _mm F1.4 It is an object of the present invention to provide a camera capable of measuring light to a low luminance of about).

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a photometric unit that divides an object field into a plurality of photometric regions of a central photometric region and a peripheral photometric region, An exposure calculation device for a camera, comprising: a photometric mode selecting means capable of selecting a part-weighted photometric mode, wherein the central portion photometric region is divided into a spot portion and an annular portion located outside the spot portion. Comparing means for comparing the photometric value of the spot portion with a predetermined value when the mode is selected; and when the photometric value of the spot portion is determined to be equal to or greater than the predetermined value, the spot portion A first center-weighted photometric value calculating unit that calculates an exposure value from the photometric value of the ring portion and the photometric value of the annular portion; and when the photometric value of the spot portion is determined to be less than a predetermined value by the comparing unit, The ring It provided a second center-weighted light metering value calculating means for calculating an exposure value only from the photometric value of the portion.

[Operation] In the present invention, the photometric value of the spot portion is compared with a predetermined value by comparing means. If the photometric value is equal to or larger than the predetermined value, the photometric value of the spot portion and the annular portion located outside the spot portion are calculated. A means for determining an exposure value in the center-weighted metering mode (first center-weighted metering value calculating means); and, if smaller than a predetermined value, an exposure value in the center-weighted metering mode from the metering value of only the annular portion. Means (second center-weighted photometric value calculating means) to determine the brightness on the low-luminance side (approximately BV-5 (50 _mm F1.4)) that is desired to be photometric in normal specifications Photometry is possible up to.

For example, dividing the object field as in the FIG. 6, the central portion C ₁
The brightness value obtained from is defined as BV _C1 . In addition, the subject
A portion corresponding to C ₁ part of Figure 6 as shown in FIG divided into spot portion A ₁ and the circular portion A _2, respectively obtained from A ₁ and A ₂ portion of the luminance values BV _A1, BV _A2 The absolute value of the difference is | BV _A2 −
BV _A1 |

Now the same scene, and metering at the same time in the first view and FIG. 6 of the photometric system, the relative scene BV _C1 and | were measured for combining about 700 scenes | BV _A2 -BV _A1. And about 7
The data of 00 is BV _{C1 [BV] on} the horizontal axis, and | BV _A2 −BV _A1 |
_[BV] was plotted, and a correlation as shown in FIG. 4 was obtained.

From this result, for dark subjects of BV5 or less, C ₁
It has been found that the luminance difference within a portion (ie, | BV _A2 −BV _A1 | _[BV] ) is often very small. Therefore, when the photometric value of the spot portion A ₁ is equal to or less than a predetermined value, be used to determine the exposure value of the center-weighted metering mode from the photometric value of only the annular section A _2, generally it can be seen that no problem. This can be known from experience, and it is because scenes with a BV of 5 or less generally have a small luminance difference even in the whole scene, such as evening scenes and night scenes. Accordingly, in such a scene, there is little case of most importance to the exposed spot portions A _1, it can be seen that no problem even using only photometric value of only the annular portion A _2.

Embodiment An embodiment according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a pattern of a six-segment light receiving element according to the present invention. The light receiving element, the center of the light receiving portion is spot portion A ₁ and the circular portion A ₂ made from the turn in the four light receiving portions A ₃ ~
With the A _6. FIG. 2 is a block diagram of an embodiment of the present invention. The luminous flux from the object field that has passed through the lens 1 of the taking lens 3 and the aperture 2 is applied to each cell (A _1-
A ₆ ) is received. Note that the six-divided light receiving element 4 is
Since the positional relationship is substantially conjugate to the imaging plane of the camera, the divided shape may be considered to be substantially the same as the object scene to be photographed. Photocurrent output from each of the cells A ₁ to A ₆ is input to the photometry circuit 5, where the aperture value AV of the taking lens ₀
And a, is converted into a luminance value BV ₁ to BV _6. Exposure calculation means 8
Is a comparison means 10 and a first center-weighted photometry value calculation means 11
And a second center-weighted photometric value calculating means 12 and an AMP algorithm processing section 13. Further, the exposure calculation means 8
It is also possible to calculate a spot metering value in the spot metering mode using only the spot portion A1, but the spot metering mode is already well known and will not be described.
This exposure calculation unit 8, the brightness value BV ₁ to BV ₆ corresponding from the photometric circuit 5 to each cell A ₁ to A _6, the aperture value from the photographing lens 3 A
V ₀ , the photometric low luminance limit value output means 6 outputs the reference lens (f =
50 _mm F1.4) metering low luminance limit UL ₁ is respectively input,
Further, either one of the center-weighted metering mode (CW) and the multi-pattern metering mode (AMP) is selected and input from the mode setting means 7. Then, when the center-weighted photometry mode CW is selected, the exposure value is calculated and output to the exposure control means 9 according to a procedure described later.

Next, an exposure calculation device according to the present invention will be described with reference to FIG. First, when a release button (not shown) is half-pressed, the exposure calculation means 8 starts calculation (S1). The exposure calculation means 8 calculates the open aperture value AV of the aperture 2 of the photographing lens 3.
₀ reads (S2), photometric low luminance threshold photometric low luminance limit of the spot portion A ₁ in the case of the output unit 6 and the reference lens was mounted (underflow value) reads UL ₁ (S
3) The underflow value BV _UF-1 of the actually mounted photographing lens 3 is calculated by the following equation: BV _UF-1 = AV ₀ -1 + UL ₁ (S4). For example, AV ₀ = 3 (F2.8), UL ₁
In the case of = -1 _[BV] , BV _UF-1 = 3-1-1 = 1 _[BV] .

Then, the exposure calculation unit 8 reads the respective luminance values BV ₁ to BV ₆ corresponding to each cell A ₁ to A ₆ calculated by the photometric circuit 5 (S
5) When the multi-pattern photometry mode AMP is selected by the mode setting means 7, go to the AMP algorithm (S7).
Comparison means when center-weighted metering mode CW is selected
The operation proceeds to 10 (S8) (S6).

In the AMP algorithm (S7), the AMP algorithm processing unit
The maximum brightness value and the maximum brightness difference are obtained from the brightness values of BV ₁ to BV ₆ by 13, and the exposure value is calculated by classifying the scene by these two parameters. Such an AMP algorithm is already disclosed in JP-A-55-114916 and JP-A-57-42026,7, and is not directly related to the present invention.

Comparison means 10 (S8) performs a comparison between a luminance value BV ₁ and underflow values BV _UF-1 spot portion _{A 1, BV 1 ≧ BV UF} -1
Of time, i.e., if as shown in FIG. 5 is spot portion A ₁ capable of measuring luminance values BV ₁ proceeds to the first center-weighted light metering value calculation unit 11 (S9), spot portion A ₁ and the circle Ring part A ₂
Request central weighted metering value CW from the luminance value BV ₁ and BV ₂ of. CW
The area ratio of the light receiving element of A ₁ and A ₂ are added value by multiplying respectively, for example, the area ratio A _1: A ₂ = 1: For 15, Given by

Further, when BV ₁ <BV _UF-1, i.e., if the spot portion A ₁ as shown in Figure 5 is not possible measured luminance value BV _1, the second center-weighted light metering value calculating means 12 ( proceeds to S10), obtains the center-weighted photometry value CW from the luminance values BV ₂ of annular section a _2. B
V ₁ <BV _UF-1 low-luminance _object- centered center-weighted photometry value
The validity determining the CW from only the luminance values BV ₂ of annular section A _2, as shown in FIG. 5, in such a low brightness, the light current output spot portion A ₁ is not obtained sufficiently accurate it is not, the photocurrent output of the annular section a ₂ is maintained sufficient accuracy has linearity even such a low intensity, and, as shown in Figure 4, such a low brightness , The spot part A ₁ and the ring part
It is clear from the fact that need to emphasize the luminance of the spot portion A ₁ luminance difference A ₂ is reduced is eliminated.

The first center-weighted photometric value calculation means 11 (S9) or the second
The center-weighted photometry value CW calculated by the center-weighted photometry value calculation means 12 (S10) is output to the exposure control means 9 (S11), and the exposure calculation ends (S12).

Although the exposure calculation device according to the present invention has been described with reference to the drawings, the present invention should not be construed as being limited to the above-described embodiments, and may be appropriately modified without impairing the spirit thereof.
Of course, improvements are possible.

[Effects of the Invention] As described above, according to the present invention, the photometric value of the spot portion is compared with a predetermined value by the comparing means. The exposure value of the center-weighted metering mode, which is almost equivalent to the method, can be determined. If the photometry value of the spot portion is smaller than a predetermined value, the photometry value of the annular portion may be represented as the exposure value of the center-weighted photometry mode in terms of scene classification. The exposure value is determined from the value, whereby the photometry can be performed up to the low-brightness-side brightness (about BV-5 (about 50 _mm F1.4)) which is desired to be photometric in the normal specification.

[Brief description of the drawings]

FIG. 1 is a pattern diagram of a six-divided light receiving element of the present invention, FIG. 2 is a block diagram of a camera exposure calculating device according to the present invention, FIG. 3 is a flowchart diagram of a camera exposure calculating device according to the present invention, Figure 4, the internal brightness difference relative to the center-weighted metering value BV _C1 | BV _A2 -BV _A1 | diagram showing the correlation of Fig. 5, the spot portion to the luminance BV a ₁ and the circular portion a ₂
FIG. 6 is a pattern diagram of a conventional five-divided light receiving element. [Description of Signs of Main Parts] 3... Photographing lens 4... 6-segment light receiving element 5... Photometric circuit 6... Photometric low-luminance limit value output unit 7. Exposure control means 10 Comparison means 11 First center-weighted photometric value calculation means 12 Second center-weighted photometric value calculation means

Claims (1)

(57) [Claims] 1. A camera comprising: a photometric unit that divides an object scene into a plurality of photometric regions including a central photometric region and a peripheral photometric region; and a photometric mode selecting unit that can select a centrally-weighted photometric mode. In the exposure calculation device of the above, the central portion photometric region comprising a spot portion and an annular portion located outside the spot portion; and a photometric value of the spot portion and a predetermined value when the central portion weighted photometric mode is selected. And a comparing unit that compares the photometric value of the spot portion and the photometric value of the annular portion when the photometric value of the spot portion is determined to be equal to or greater than a predetermined value. A first center-weighted photometric value calculating means; and a second calculating means for calculating an exposure value only from the photometric value of the annular portion when the comparing means determines that the photometric value of the spot portion is less than a predetermined value. Central part of An exposure calculation device for a camera, comprising: weighted photometric value calculation means.