JP2002314874A - Digital camera and its exposure control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a digital camera in which highly accurate automatic exposure control can be carried out by a specified hue region in a photographed image through simple operation. SOLUTION: A CPU 25 controls an iris motor driver 18 and an exposure control section 22 to perform automatic exposure control of an objective image picked up by means of a CCD 12. When a photographer pushes a hue AE switch 24 to designate a specified hue part for matching exposure of the objective image at the time of performing automatic exposure control by hue (hue AE), hue at the designated part is calculated. A hue range detecting section 27 extracts a hue region approximate to the hue at the designated part, and an average luminance calculating section 28 calculates the average luminance of the approximate hue region. The CPU 25 performs exposure control based on the calculated average luminance, the image of the object is picked up upon pushing a release switch 23, and image data of the object image thus obtained is recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital camera for electronically capturing and recording a still image or a moving image of a subject and an exposure control method thereof.

[0002]

2. Description of the Related Art In a digital camera that electronically captures an image using an image sensor such as a CCD, generally, in order to obtain a subject image of good image quality, an exposure amount is adjusted so that an image can be captured with an appropriate exposure amount. ing. For this exposure adjustment,
Automatic exposure control (AE) for adjusting an exposure amount according to the brightness of a subject or the like is widely used. In automatic exposure control, various AE methods have been developed to detect the brightness of a subject image and determine an exposure level at which an appropriate value is obtained.

[0003] Japanese Patent Application Laid-Open No. 9-284784 discloses a method of internally dividing signal levels of a specific luminance region and a flesh-color region in the imaging screen by the ratio of the extracted area to the extracted skin color region. A color imaging apparatus that automatically switches an exposure control mode according to a value is disclosed. According to this method, regardless of the brightness of the background,
The exposure amount can be controlled so that the brightness of the main subject becomes appropriate. Also, JP-A-11-13656
Japanese Patent Application Laid-Open No. 8 (1999) -1995 discloses that an exposure level is determined by detecting a main subject based on an area specified on an imaging screen of a display unit, or by setting an exposure level based on luminance in a closed curve drawn as a movement locus on a touch panel of the display unit. A touch panel operated camera for determining is disclosed. According to this method, exposure control can be performed with a simple operation irrespective of the position of the main subject, with emphasis on the main subject intended by the photographer.

[0004]

In the conventional AE system described above, in the system disclosed in Japanese Patent Application Laid-Open No. 9-284784, since the detection accuracy of the skin color region is particularly poor in dark areas, depending on the condition of the subject such as a dark person. There is a problem that the accuracy of the exposure control is reduced. Also, JP-A-11-1
In the method disclosed in Japanese Patent No. 36568, since the photographer needs to operate the touch panel to indicate the main subject, there is a problem that the photographing operation is time-consuming and weak in shutter chance. In addition, since a touch panel is indispensable, there is a problem that the cost is increased.

The AE system based on spot photometry, which is also used in conventional film cameras, is intended for experienced persons who need experience and training to specify a photometry point, and are inexperienced in shooting operation. When used by an operator, an appropriate value of exposure may not be obtained, and there is a problem that operation is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a digital camera capable of performing highly accurate automatic exposure control by a simple operation using a designated hue region in a photographed image, and an exposure control method therefor. The purpose is to provide.

[0007]

According to the present invention, there is provided a digital camera, comprising: an image pickup unit for picking up an image of a subject; a hue designating unit for designating a predetermined hue portion for adjusting exposure in the subject image in accordance with a photographer's operation; A hue region extracting unit that extracts a hue region close to the designated hue region, an average luminance calculating unit that calculates an average luminance in the extracted approximate hue region, and, based on the average luminance,
Exposure control means for controlling the brightness of the subject image obtained via the imaging means.

Preferably, when a plurality of hue regions are designated by the hue designation unit, the hue region extraction unit extracts approximate hue regions for each hue. It is characterized in that an average luminance in an approximate hue region of a plurality of hues is calculated.

Preferably, there is provided an area selecting means for selecting an application area in a subject image from which an approximate hue area is to be extracted by the hue area extracting means in accordance with a photographer's operation or predetermined shooting conditions. The hue region extracting means extracts an approximate hue region related to the designated hue portion in the application region.

Preferably, the area selecting means includes:
The application area is selected in accordance with a composition assist frame that assists in determining the composition of the subject image.

The exposure control method for a digital camera according to the present invention includes a hue designation step of designating a predetermined hue portion to be adjusted for exposure in a subject image obtained via an imaging means in accordance with an operation of a photographer; A hue region extracting step of extracting a hue region close to the part; an average luminance calculating step of calculating an average luminance in the extracted approximate hue region; and controlling the brightness of the subject image based on the average luminance. An exposure control step;
It is characterized by having.

Preferably, in the hue region extracting step, when a plurality of hue parts are designated by the hue designation step, an approximate hue region is extracted for each hue, and in the average luminance calculation step, It is characterized in that an average luminance in an approximate hue region of a plurality of hues is calculated.

Preferably, the method further comprises an area selecting step of selecting an application area in the subject image from which the approximate hue area is to be extracted in accordance with a photographer's operation or predetermined shooting conditions. Wherein an approximate hue region relating to the designated hue region is extracted in the application region.

Preferably, in the area selecting step, the applicable area is selected according to a composition assisting frame for assisting composition determination of the subject image.

According to the present invention, a predetermined hue portion to which exposure is desired to be specified is specified, a hue region close to the hue portion is extracted, an average luminance in the extracted approximate hue region is calculated, and the calculated average is calculated. By performing the exposure control based on the luminance, the photographer can extract a region having a close hue from the subject image by a simple operation of simply specifying the hue of the main subject of interest, and obtain an average luminance of the approximate hue region. Thus, the optimum exposure level can be determined, and it is possible to easily and accurately capture an image with good exposure and high satisfaction.

When a plurality of hue regions are designated, an approximate hue region is extracted for each hue, and the average luminance in the approximate hue region of the plurality of hues is calculated, so that the photographer pays attention to the subject. It is possible to determine the appropriate exposure amount more finely for the hue of.

In addition, an application area in the subject image from which an approximate hue area is to be extracted is selected in accordance with a photographer's operation or a predetermined imaging condition, and an approximate hue area related to a designated hue portion is selected in the application area. By extracting, the noise component in the subject image at the time of extracting the approximate hue area can be removed, and the S / N of the average luminance calculation is improved, so that more accurate automatic exposure control can be performed. The application area is selected, for example, by a photographer's operation, or appropriately selected according to predetermined shooting conditions. At this time, when using a composition assist frame to assist in determining the composition of the subject image at the time of photographing, the photographer can select an arbitrary area in this frame, or can use a type of frame used under predetermined photographing conditions. May be used to select a predetermined area where the main subject is located. This makes it possible to extract an area approximating the specified hue from an appropriate area according to the subject or the like, and to execute automatic exposure control based on the hue with high accuracy by a simple operation.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a functional configuration of a digital camera according to one embodiment of the present invention.

A digital camera 10 for electronically capturing a still image or a moving image of a subject is provided with an optical system 11 including an imaging lens and a diaphragm as an imaging unit (imaging means), and a CCD 12 as an imaging device. ing. The optical system 11 includes an iris motor driver 18 that drives an iris motor that displaces a stop provided in the optical system,
An AF motor driver 19 that drives an autofocus (AF) motor that displaces the focusing lens is connected.

On the output side of the CCD 12, a CDS analog decoder 13, a white balance amplifier 14, a gamma correction circuit 15, a dot-sequencing circuit 16, and an A / D converter 17 are provided. A digital image signal is output.
The white balance amplifier 14 is connected to an exposure control unit (EVR) 22 for controlling the exposure of the photographed image, so that the gain of the white balance amplifier 14 is controlled. The output of the A / D converter 17 is transmitted to the main memory 21 via the memory controller 20.
Image data of the photographed subject is stored in the main memory 21.

A release switch 23 for the photographer to give an operation instruction for photographing, and a hue AE switch 24 for giving an operation instruction for automatic exposure control (hereinafter referred to as hue AE) based on hue described later are provided. ing. A CPU 25 is provided as control means for controlling each unit of the apparatus. The CPU 25 is connected to the iris motor driver 18, the AF motor driver 19, the exposure control unit 22, the release switch 23, the hue AE switch 24, and the data bus 26. . The data bus 26 includes a hue range extraction unit 27, an average luminance calculation unit 28, a compression / expansion unit 29, an MPEG encoder & decoder 30, an YC signal creation unit 31, an LCD driver 34, a speaker driver, together with the CPU 25 and the memory controller 20. 36, an external memory interface 38, and a communication interface 40 are connected. The CPU 25 and the iris motor driver 1
8, an optical system 11, an exposure control unit 22, and a white balance amplifier 14 constitute an exposure control unit.

The hue range extractor 27 has a hue AE, which will be described later.
And extracts a range of hues similar to the hues of the region designated by the photographer, and constitutes a hue region extracting means together with the CPU 25. The average luminance calculation unit 28 calculates the average luminance of the hue range extracted by the hue range extraction unit 27, and forms an average luminance calculation unit together with the CPU 25. The compression / decompression unit 29 performs a compression process and a decompression process of image data according to the JPEG method or the like. MP
The EG encoder & decoder 30 encodes moving picture data of the MPEG system and decodes moving picture data that has been MPEG-compressed. YC signal creation unit 3
Numeral 1 separates and generates a luminance signal Y and color difference signals RY and BY for generating an NTSC video signal. The ratio of the luminance signal Y and the color difference signals RY and BY is set to 4: 2: 2 from 4: 4: 4 in the subsequent stage of the YC signal creation unit 31.
And an NTSC encoder 33 that generates and outputs an NTSC video signal.

The hue range extracting section 27, the average luminance calculating section 28, the compressing / expanding section 29, the MPEG encoder &
Decoder 30, YC signal creation unit 31, color conversion unit 32, N
The TSC encoder 33 may be configured by a dedicated signal processing circuit, may be configured by software processing in the CPU 25, or may be configured by a function provided in a signal processing circuit such as a DSP.

The LCD driver 34 has a liquid crystal display element (L
A CD) 35 is connected, and an image of a subject to be photographed, a recorded image after photographing, various status displays, setting screens, and the like are displayed on the screen of the LCD 35. The hue AE switch 24 and the LCD 35 constitute a hue designation unit. A speaker 37 is connected to the speaker driver 36 so that various operation sounds at the time of photographing or the like are reproduced and output.

The digital camera 10 configured as described above
In the above, the image of the subject is
Is imaged on the image pickup surface of the image sensor and photoelectrically converted. An imaging signal output from the CCD 12 is output to a CDS analog decoder 13.
After performing the correlation double sampling to cancel the noise component, the white level of the color image signal is adjusted by the white balance amplifier 14. Then, the γ correction is performed by the γ correction circuit 15, and the A / D
The data is A / D converted by the converter 17 and output as digital image data. This digital image data is stored in the main memory 21 via the memory controller 20.

The digital image data is displayed on the screen of the LCD 35 as a subject image being photographed. The photographer shoots a still image or a moving image of the subject by pressing and turning on the release switch 23 while looking at the subject image. The photographed image data is subjected to compression processing in a compression / decompression unit 29 or MPEG compression encoding in an MPEG encoder & decoder 30, and to an external memory 39 via an external memory interface 38 or an external server via a communication interface 40. 41, and the captured image is recorded. The photographed image data is converted into an NTSC video signal via a YC signal creation unit 31, a color conversion unit 32, and an NTSC encoder 33 and output.

Next, the hue AE used as automatic exposure control in this embodiment will be described in detail below. In the present embodiment, when performing automatic exposure control, an area having a hue similar to the hue of the area (spot metering area) specified by the photographer in the image of the subject is extracted, and the average luminance of the approximate hue area is calculated. Then, the exposure amount is controlled based on the obtained average luminance.

FIG. 2 is a flowchart showing an operation procedure mainly for automatic exposure control at the time of photographing according to the first embodiment, and mainly shows the operation of the CPU 25. In the first embodiment, first, in step S11, it is determined whether or not the hue AE switch 24 has been pressed and turned on. Here, the hue AE switch 24 is turned on in the same manner as general automatic exposure control by spot metering. When an area to be measured by being pressed is specified, the hue of the spot photometric area is calculated in step S12. The hue of such a predetermined area may be calculated using a known image signal processing technique.
The level of each color component of R, G, and B is obtained to obtain a hue value in a color space.

Next, in step S13, an area close to the hue of the spot photometric area is extracted by the hue range extracting section 27, and in step S14, the average luminance Eaverage of the area obtained by the average luminance calculating section 28 is calculated. Then, in step S15, the exposure amount control is performed by controlling the iris motor driver 18 and the exposure control unit 22 based on the value of the obtained average luminance Eaverage. The average luminance may be calculated by a simple average of the luminance values in the approximate hue region, or may be calculated by using a weighted average. In the weighted average, for example,
An appropriate average luminance can be calculated by a weighting method such as weighting in the vicinity of the spot metering area, or weighting a portion close to the hue and a portion slightly away from the hue based on the approximate hue level. In addition, the extracted approximate hue region is displayed in a subject image displayed on a viewfinder or a display unit of a liquid crystal display element or the like so as to be distinguished from other regions, for example, by being painted in red so that a photographer can easily determine the region. You may do it.

Then, in step S16, it is determined whether or not the release switch 23 has been pressed and turned on. If the release switch 23 has been pressed and the shutter has been released, the image is taken by the CCD 12 in step S17. The image data obtained by imaging in step S18 is stored in the main memory 21 or transferred to the external memory 39 or the external server 41 for recording.

By using such a hue AE,
For example, when the photographer specifies a part of the face of the subject as the spot metering area with the hue AE switch 24, the hue is set in the spot metering area specified in the subject image, such as the color of the face of the person or the skin of the hand. A region of an approximate hue is extracted, and automatic exposure control is performed based on an average luminance of the approximate hue region. For example, when photographing a plurality of persons, if a part of the face of a certain person is designated as a spot metering area by the hue AE switch 24, an area where the hue such as the face or hand of each person in the subject image is approximated. Are extracted, and automatic exposure control is performed based on the average luminance of the extracted approximate hue region.

[0032] Thus, by a simple operation of designating only one spot in the subject image as a spot photometry area for hue AE, the exposure can be properly and accurately performed without being influenced only by the brightness of the spot photometry area. The quantity control becomes executable.

In a digital camera, the hue A
An exposure mode can be switched by providing an E mode and another AE mode such as a spot metering AE mode.
It is also possible to provide a configuration in which only the E mode is provided and hue detection is always performed to perform automatic exposure control. When taking a picture in the hue AE mode, the exposure calculation may be performed by operating a dedicated hue AE switch, or the hue AE switch may be integrated with the release switch to form a multi-stage release switch. Exposure calculation may be performed when is pressed halfway down one step.

FIG. 3 is a flowchart showing an operation procedure mainly for automatic exposure control at the time of photographing according to the second embodiment of the present invention. In the second embodiment, a plurality of hues are selected, regions of hues similar to the hues are extracted, the average luminance of these approximate hue regions is calculated, and the exposure amount control is performed based on the obtained average luminance. Here is an example of the operation.

First, in step S21, the initial value of the counter in the CPU 25 is set to i = 0, and in step S22, it is determined whether the hue AE switch 24 has been pressed and turned on. Here, when the hue AE switch 24 is pressed and a region for photometry is instructed, the hue of the spot photometry area is calculated in step S23, and in step S24,
The hue range extraction unit 27 extracts a region close to the hue of the spot photometry area.

Next, in step S25, the average luminance E [i] of the area obtained by the average luminance calculating section 28 is calculated.
In step S26, the counter value in CPU 25 is set to i = i
+1. Then, in step S27, it is determined whether or not the selection of the hue to be subjected to photometry by the hue AE switch 24 has been completed. If another hue is to be selected, the processes in steps S22 to S26 are repeated. As a result, the hues at a plurality of locations in the subject image are selected as the spot metering areas, and the average luminance of the approximate hue area for each hue is calculated. The determination of the end of the selection of the photometric position for the hue AE may be made a preset number of times, or the photographer may set the release switch 23 in two stages and press the release switch 23 halfway down one stage to give the AF instruction. Or may be regarded as an end when another operation is performed, or a switch for instructing an end of the hue selection may be provided.

If the selection of the hue to be photometrically completed is completed in step S27, the process proceeds to step S28.
The average luminance Eaverage of the luminance from [1] to E [i] is calculated, and in step S29, based on the value of the average luminance Eaverage, the iris motor driver 18 and the exposure control unit 2
2 to control the exposure amount. next,
In step S30, it is determined whether or not the release switch 23 has been pressed and turned on.
If No. 3 is pressed and the shutter is released, step S3
In step S1, an image is picked up by the CCD 12, and in step S32, the image data obtained by the image pickup is stored in the main memory 21 or transferred to the external memory 39 or the external server 41 for recording.

As described above, in the second embodiment, a plurality of spots in a subject image are designated, a region of a hue approximated with respect to a plurality of hues is extracted, an average luminance for each hue is calculated, and a plurality of hues are calculated. The average luminance of the whole hue is calculated, and the exposure amount is controlled based on the average luminance. As a result, it is possible to more finely determine the appropriate exposure amount for the hue of the subject to which the photographer has paid attention.

FIG. 4 is an explanatory diagram showing an area selection of hue AE in the third embodiment of the present invention, and FIG. 5 is a flowchart showing an operation procedure mainly in automatic exposure control at the time of photographing according to the third embodiment. .

The third embodiment exemplifies a case in which the CPU 25 or the like includes an area selecting means, selects a partial area where a main subject is located in a subject image, and performs hue AE in the selected applicable area. . 2. Description of the Related Art Some digital cameras have a composition assist function for assisting in determining a composition of a subject by displaying a frame serving as a shooting guide on a viewfinder or a display unit of a liquid crystal display element in which a subject image is displayed during shooting.

The frame for composition assistance includes a vertical and horizontal three-divided frame 51 which uses vertical and horizontal lines and their intersections as a reference when photographing the landscape shown in FIG.
A commemorative photographing frame 52 used for arranging the subject in the lower part of the center at the time of commemorative photographing shown in FIG. There is a frame 53 and the like. When hue AE is performed in photographing using such frames 51, 52, and 53, an area where a main subject is located in each frame in the subject image 50 is selected as a selection area 54,
As 55 and 56, an area approximating the hue of the designated spot metering area is extracted in the selected areas 54, 55 and 56, and the average brightness of the approximate hue area is obtained to perform automatic exposure control.

The operation procedure of the hue AE in such a selected area will be described. First, in step S41, a hue AE application area such as a selection area based on the frame is selected, and in step S42, it is determined whether the hue AE switch 24 has been pressed and turned on. Where hue AE
When the switch 24 is pressed to specify a photometry area, the hue of the spot photometry area is calculated in step S43, and in step S44, the hue is extracted by the hue range extraction unit 27 and is close to the hue of the spot photometry area. The area is extracted from the selected area. The selected area to which the hue AE is applied and the extracted approximate hue area are, for example, filled with red in a subject image displayed on a finder or a display unit of a liquid crystal display element so that a photographer can easily determine the selected area. For example, the outline of the area may be displayed so as to be distinguished from other areas.

Next, in step S45, the average luminance Eaverage of the area determined by the average luminance calculator 28 is calculated. In step S46, the iris motor driver 18 and the exposure controller 22 are controlled based on the calculated average luminance Eaverage. By controlling, exposure amount control is performed. Then, in step S47, it is determined whether or not the release switch 23 has been pressed and turned on. If the release switch 23 has been pressed and the shutter has been released, an image is taken by the CCD 12 in step S48, and step S49 is performed.
Is stored in the main memory 21 or transferred to the external memory 39 or the external server 41 for recording.

Since the arrangement of the main subject and the background noise-like area that is not important for exposure control are basically almost determined by the composition of the subject, the hue is adjusted according to the composition assist frame as described above. By setting the AE application area, it is possible to exclude an unnecessary area that becomes a noise component in calculating the average luminance of the approximate hue area.

In this case, a region necessary for the hue AE in the subject image may be selected or an unnecessary region may be excluded. Further, the hue AE application area may be set to an area predetermined by the composition assist frame as described above, or may be an area required by the photographer among nine areas in a vertical and horizontal three-divided frame. Unnecessary areas can be selected. Further, regardless of the frame, the photographer can set an arbitrary area as an application area or an exclusion area of the hue AE, or a predetermined range based on the spot photometry area.

As described above, in the third embodiment, the application area of the hue AE is limited, so that the noise component in the subject image in the hue AE is removed and the S / N of the average luminance calculation is performed.
Therefore, it is possible to perform more accurate automatic exposure control.

As described above, by using the hue AE of the present embodiment, for example, by specifying a dark area of a flesh color in a subject image as a spot metering area, the flesh color detection accuracy is reduced even if the flesh color luminance varies. Can be avoided, and an appropriate exposure level can be obtained by controlling the exposure amount for a region of a predetermined hue included in the main subject.

Further, when photographing a large number of people, there are cases where the brightness varies substantially in the same hue depending on the state of the illumination light such as sunshine and shade, but the average brightness of these approximate hue regions is large. Can be adjusted to
It is possible to set an optimal exposure level without unfairness. Note that the present invention can be similarly applied to the case where the hue of the main subject is not limited to the flesh color but another hue. Also, as in the second embodiment, the average exposure is determined for a plurality of hues to obtain the optimum exposure level. Can also be set. Therefore, the present embodiment is particularly effective when the main subjects have the same system of hues and the like, and highly accurate automatic exposure control can be executed by a simple operation.

In the present embodiment, a simple hue for designating the hue of the main subject of interest, such as pressing the hue AE switch with the hue portion desired to be exposed in the spot metering area in the subject image such as the viewfinder or the like and pressing the hue AE switch. By the operation, an area having a close hue can be extracted from the subject image, and an optimum exposure level can be determined based on the average luminance of the approximate hue area. As a result, even a photographer who is not very skilled can easily and accurately take an image with good exposure and high satisfaction.

[0050]

As described above, according to the present invention, there is provided a digital camera capable of performing high-precision automatic exposure control by a simple operation using a designated hue region in a photographed image, and an exposure control method therefor. There are effects that can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a functional configuration of a digital camera according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation procedure mainly for automatic exposure control during photographing according to the first embodiment.

FIG. 3 is a flowchart illustrating an operation procedure mainly related to automatic exposure control during photographing according to a second embodiment.

FIG. 4 is an explanatory diagram illustrating an area selection of a hue AE according to a third embodiment.

FIG. 5 is a flowchart illustrating an operation procedure mainly for automatic exposure control during photographing according to a third embodiment.

[Explanation of symbols]

 11 Optical System 12 CCD 14 White Balance Amplifier 17 A / D Converter 18 Iris Motor Driver 19 AF Motor Driver 20 Memory Controller 21 Main Memory 22 Exposure Control Unit (EVR) 23 Release Switch 24 Hue AE Switch 25 CPU 27 Hue Range Extraction Unit 28 Average luminance calculation unit 29 Compression / expansion unit 30 MPEG encoder & decoder 35 LCD 39 External memory

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H002 DB14 DB17 DB31 HA04 JA07 2H054 AA01 5C022 AA13 AB17 AC13 AC42 AC69 AC71

Claims (8)

[Claims] An imaging unit that captures an image of a subject; a hue designating unit that designates a predetermined hue portion for adjusting exposure in the subject image in accordance with a photographer's operation; and a hue region close to the designated hue portion. A hue region extracting unit to be extracted; an average luminance calculating unit that calculates an average luminance in the extracted approximate hue region; and controlling a brightness of a subject image acquired via the imaging unit based on the average luminance. A digital camera, comprising: exposure control means; 2. The method according to claim 1, wherein the hue region extracting unit extracts an approximate hue region for each hue when the plurality of hue regions are designated by the hue designating unit. 2. The digital camera according to claim 1, wherein an average luminance in the approximate hue region is calculated. 3. An application area in a subject image from which an approximate hue area is extracted by the hue area extraction means,
The image processing apparatus according to claim 1, further comprising: an area selecting unit configured to select an area based on an operation of a photographer or a predetermined imaging condition, wherein the hue area extracting unit extracts an approximate hue area related to the designated hue part in the application area. 3. The digital camera according to 1 or 2. 4. The digital camera according to claim 3, wherein the area selection unit selects the applicable area according to a composition assist frame that assists in determining a composition of the subject image. 5. A hue designating step of designating a predetermined hue portion to be adjusted for exposure in a subject image obtained via an imaging means in accordance with a photographer's operation, and a hue extracting a hue region close to the designated hue portion. An area extracting step; an average luminance calculating step of calculating an average luminance in the extracted approximate hue area; and an exposure controlling step of controlling brightness of the subject image based on the average luminance. Exposure control method for digital cameras. 6. In the hue region extracting step, when a plurality of hue parts are designated by the hue designation step, an approximate hue region is extracted for each hue, and in the average luminance calculation step, the plurality of hue regions are extracted. 6. The exposure control method for a digital camera according to claim 5, wherein an average luminance in the approximate hue region is calculated. 7. An area selection step of selecting an application area in a subject image from which the approximate hue area is to be extracted, according to a photographer's operation or a predetermined shooting condition, wherein, in the hue area extraction step, 7. The exposure control method for a digital camera according to claim 5, wherein an approximate hue region related to the designated hue region is extracted in the application region. 8. The exposure control method for a digital camera according to claim 7, wherein in the area selection step, the applicable area is selected according to a composition assist frame that assists in determining the composition of the subject image. .