JPH10322592A - Method and device for controlling electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a high luminance part from being white and to set a main object to appropriate brightness by relating and deciding an exposure and gradation based on the luminance distribution of images picked up by reference exposure conditions for preliminary image pickup. SOLUTION: For image signals converted in a CDD 104, a luminance processing and a chrominance processing are executed in a process circuit 107 and they are outputted to an output circuit 113 as digital video signals composed of luminance signals and color difference signals. A main CPU 110 generates the histogram of the luminance distribution from the digital value of the luminance signals for respective picture elements image picked up by the reference exposure conditions for the preliminary image pickup. In the luminance processing in the process circuit 107, the histogram of the luminance distribution is referred to, and when a luminance distribution width is excessive for instance, the exposure at the time of photographing smaller than the preliminary image pickup exposure conditions is decided. Further, estimated luminance distribution is generated based on the exposure in photographing and gradation characteristics are decided so as to turn the luminance area of a high distribution frequency to a reference luminance value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling an electronic camera, which is called a digital camera, and more particularly to a technique for controlling an entire image to have appropriate brightness.

[0002]

2. Description of the Related Art In recent years, an optical image of a subject has been captured by an imaging lens,
Solid-state imaging device (CCD) via an optical imaging system such as an aperture
2. Description of the Related Art An electronic camera configured to record an electric image signal output after being photoelectrically converted by the image pickup device on a recording medium has been put to practical use.

A general automatic exposure control (hereinafter, referred to as AE) of this kind of electronic camera is such that a value obtained by integrating and averaging the luminance signal levels of the entire image detected by the image sensor becomes an appropriate level. The aperture and the exposure time (both are hereinafter referred to as exposure) are controlled. In addition, there is a method in which the weight of the central portion of the image is increased, the luminance signal level is integrated, and the exposure is controlled based on the integrated value.

[0004]

However, in a general system using a value obtained by integrating and averaging the luminance signal levels of the entire captured image, for example, if an image has an extremely high luminance portion, the integrated value Is increased under the influence of the influence, and if the exposure amount is determined based on the average value, the image becomes dark as a whole, and the S / N ratio also deteriorates. In addition, since the exposure amount is determined according to the average value of the high-brightness part and the low-brightness part, the high-brightness part tends to be too bright and become a white flying image.

[0005] Further, in the case of exposure control in which the center of the screen is weighted, the above problem cannot be solved if an extremely high luminance portion is located in a portion having a large weight. In addition, there is a method in which the exposure amount is corrected while performing a plurality of imagings, and the exposure control is performed so that the main subject has an appropriate brightness. In particular, the problem that the high-brightness portion becomes too bright and becomes an image flying white has not been able to be solved only by exposure control.

The present invention has been made in view of such conventional problems. In an electronic camera, a main subject has an appropriate brightness, an optimum S / N ratio can be set, and a high brightness portion can be set. An object of the present invention is to provide a high quality image by preventing the image from flying white.

[0007]

For this reason, the control method (apparatus) for an electronic camera according to the invention of claim 1 (claim 12) is (as shown in FIG. 1) (by the luminance distribution state detection means). A luminance distribution state of an image is detected based on an image signal captured by an image sensor under predetermined conditions, and an exposure amount and a gradation are determined based on the luminance distribution state of the image (by an exposure amount determining unit and a gradation characteristic determining unit). It is characterized in that it is determined in association with characteristics.

[0008] In this way, by appropriately determining the exposure amount and the gradation characteristic based on the luminance distribution state of the image, it is possible to make the main subject have appropriate brightness. It is possible to control so as to obtain an appropriate brightness even for a portion other than the subject, and it is also possible to improve the S / N ratio. The electronic camera control method (apparatus) according to claim 2 (claim 13) corrects the image signal based on the determined exposure amount and gradation characteristic to obtain a second image signal. It is characterized by obtaining.

With the above arrangement, by correcting the image signal based on the determined exposure amount and gradation characteristics, appropriate brightness can be obtained for the main subject and the portions other than the main subject, respectively, and the S / N ratio can be improved. Can be obtained. According to a third aspect of the present invention, there is provided a control method (apparatus) for an electronic camera, wherein the exposure amount and the gradation characteristic are determined by the exposure amount determining means and the gradation characteristic determining means. The exposure amount is determined based on the state, and the gradation characteristic is determined based on the determined exposure amount.

[0010] In this case, first, the exposure amount is determined based on the luminance distribution state, and then the gradation characteristic is determined based on the determined exposure amount, thereby performing a simple calculation. The exposure amount and the gradation characteristics can be determined in a well-balanced manner. Further, according to the control method (apparatus) of the electronic camera according to the invention of claim 4 (claim 15), when the difference in luminance in the luminance distribution state of the image is large (by the exposure amount determining means), It is characterized in that it is determined to be small, and when the difference in luminance is small, the exposure amount is determined to be large.

In this way, when the luminance difference in the luminance distribution state of the image is large, the exposure amount is determined to be small, so that the high luminance portion occupied in the image is first reduced, and the image which has flickered white Can be reduced. Note that, by reducing the exposure amount, the brightness of the main subject usually becomes appropriate without excessively brightening the brightness of the main subject. Correction can be made with the gradation characteristics so that the brightness increases.

Conversely, when the difference in luminance in the luminance distribution state of the image is small, the exposure amount is determined to be relatively large, so that the S / N ratio is first increased while widening the luminance distribution to secure an appropriate contrast. Improve. Also, if the brightness of the main subject part becomes excessive as a result of increasing the exposure amount,
Correction can be made with gradation characteristics so that the brightness of the main subject portion decreases.

According to a fifth aspect of the present invention, in the electronic camera control method (apparatus), the luminance distribution state is a histogram, and the magnitude of the luminance distribution is determined based on a maximum luminance of the image signal. The difference or ratio between the luminance of A% frequency and the luminance of B% from the minimum luminance of the image signal (however, 0 ≦ A ≦ 10 and 0 ≦ B ≦ 10). In this way, when determining the exposure amount and the gradation characteristic in association with each other, it is possible to use a histogram in which the distribution width is appropriately set, and thus determine the exposure amount and the gradation characteristic to appropriate values. Can be.

Further, according to the electronic camera control method (apparatus) of the present invention, when the luminance distribution is small (by the gradation characteristic determining means), the gain is larger than the reference gain. It is characterized by determining such a gradation characteristic. In this way, when the luminance difference is small and the luminance distribution is small, such as when the subject is a printed matter, the gradation characteristic is determined so that the gain is larger than the reference gain and becomes brighter than the standard. Accordingly, the white background of the document as the subject can be made closer to white, and a natural image can be obtained.

According to a seventh aspect of the present invention, there is provided a control method (apparatus) for an electronic camera, wherein the gradation characteristic is determined (by the gradation characteristic determining means) when the luminance distribution is small. In addition, it is possible to set both a gradation characteristic in which the gain is larger than the reference or the reference gain and a gradation characteristic in which the gain is equal to or less than the reference gain.

In this way, uniform gray (gray)
Gray can be reproduced when the subject is imaged. Otherwise, the image will look whitish. Claim 8
A control method (apparatus) for an electronic camera according to the invention of claim 19 is based on the luminance distribution state of the image (by the exposure amount determining means and the gradation characteristic determining means). It is characterized in that an exposure amount and a gradation characteristic are determined so as to obtain luminance.

In this manner, the main subject portion is usually photographed in a large size and is to be arranged at the center, so that the luminance region having a high frequency has a high probability of being the main subject portion. The part can be controlled to have appropriate brightness. Further, the control method (apparatus) for an electronic camera according to the invention of claim 9 (claim 20) is such that the luminance at the center of the image becomes the reference luminance (by the exposure amount determining means and the gradation characteristic determining means). , The exposure amount and the gradation characteristics are determined.

In this way, the main subject portion is usually photographed in a large size and is arranged at the center, so that the luminance region having a high frequency has a high probability of being the main subject portion. The part can be controlled to have appropriate brightness. Further, the control method (apparatus) for an electronic camera according to the invention of claim 10 (claim 21) is such that the average luminance of the entire image (by the exposure amount determining means and the gradation characteristic determining means) becomes the reference luminance. , The exposure amount and the gradation characteristics are determined.

This makes it possible to appropriately control the average brightness of the entire image. An electronic camera control method (device) according to the invention of claim 11 (claim 22)
Is characterized in that a gradation characteristic is determined (by a gradation characteristic determining unit) based on a luminance distribution state of an image captured again using the exposure amount determined by the exposure amount determining unit.

In this way, the gradation characteristic can be determined with higher accuracy based on the luminance distribution state of the image actually picked up using the exposure amount appropriately determined, and the image quality can be improved. Can be improved as much as possible.

[0021]

Embodiments of the present invention will be described below. FIG. 2 shows a hardware configuration of an electronic camera provided with the control device according to the present invention. In the figure, an imaging lens 101, a focus lens 102, an iris diaphragm 103
An optical image of a subject obtained through an optical imaging system having the same is formed on a solid-state imaging device, for example, a CCD 104.
The focus lens 102 and the iris diaphragm 103
Are the lens drive circuit 121 and the iris drive circuit 120
, Respectively.

The CCD 104 photoelectrically converts the formed light image into a charge amount, and outputs the charge amount as an analog electric image signal by a transfer pulse from the CCD drive circuit 7. The analog electric image signal output from the CCD 4 is
Noise is reduced by a CDS (correlated double sampling) circuit, and gain is adjusted by AGC. Then, after being converted into a digital image signal by the A / D converter 106, it is subjected to luminance processing and color processing by the process circuit 109, and a digital video signal (luminance signal and color difference signal)
Is converted to Here, as a configuration according to the present invention, preliminary imaging is performed under predetermined conditions in the luminance processing, a distribution state of digital values of the luminance signal is detected, and an exposure amount at the time of shooting described later is determined based on the luminance distribution state. The gradation characteristic is determined in association with the gradation characteristic, and gradation processing of the luminance signal is performed based on the gradation characteristic. This will be described later in detail.

The main CPU 110 controls the operation of each section, and the strobe 116 driven by the light emitting circuit 115 is controlled so as to emit light during photographing. Also,
The AE (automatic exposure amount control), AWB (white balance adjustment), and AF (automatic focus control) processes are all performed under the control of the main CPU 110 using data of the imaging surface. Here, as the configuration according to the present invention, the exposure amount of the AE is determined based on the luminance distribution state as described later in detail. These processes are performed by the process circuit 107 supplying data, the main CPU 110 performing arithmetic processing, and controlling the aperture drive circuit 120, the lens drive circuit 121, the CCD drive circuit 125, and the color processing circuit in the process circuit 107. Do. Further, the main CPU 110 operates the operation panel 1.
Each part is controlled in accordance with the operation state of various switches (power switch, release switch, reproduction switch, etc.), and necessary information is displayed on the liquid crystal display section 131.

Here, the case where the main CPU 110 controls the whole still video camera has been described.
The configuration may be such that the PU and the main CPU share the functions. When recording this digital video signal, the compression / decompression circuit 1
At 08, data compression is performed. Then, the data is recorded by the recording / reproducing circuit 109 on the memory card 111 composed of an SRAM, a flash memory, or the like.

At the time of reproduction, compressed data of the digital video signal stored in the memory card 111 is read by the recording / reproducing circuit 109. Then, the compressed data is expanded in the compression / expansion circuit 108 to return the digital video signal to the original size. Then, the signal is converted into an analog video signal by the D / A converter 112, and output to an external device as a video signal of a predetermined level by the output circuit 113.

In the through reproduction, the process circuit 10
7, the digital video signal is directly sent to the D / A converter 112, and the image captured by the CCD 104 is continuously output to the outside as a video signal in real time. Next, a process of determining the exposure amount and the gradation characteristic, which is executed by the main CPU 110 (or a sub CPU not shown), will be described.

FIG. 3 shows a flowchart of the basic processing. In FIG. 1, in step 1, a luminance distribution state is detected based on a digital value of a luminance signal for each pixel imaged under predetermined conditions including predetermined exposure amount (exposure time and aperture amount) conditions. The luminance distribution state is a luminance or specific color histogram or a cumulative histogram. In the present embodiment, specifically, a histogram of 12-bit luminance digital values is created.

In step 2, the exposure amount (exposure time and aperture amount) at the time of photographing and the gradation characteristic are determined in association with each other based on the luminance distribution state. "Determining the exposure amount and the gradation characteristics in association with each other" means (1) increasing the intermediate value in the gradation table when increasing the exposure, or (2) when increasing the exposure due to low contrast and increasing the exposure. Lower the median value or (3) If the brightness difference or contrast is low, set a higher exposure.However, at this time, the gradation curve is not converted to the standard brightness, but the brightness becomes higher than the standard. It refers to determining a tone curve, etc., and refers to changing a gradation characteristic to a predetermined characteristic depending on whether the exposure amount is raised or lowered from a predetermined value.

Next, an embodiment for determining the exposure amount and the gradation characteristic in the step 2 will be described. The first embodiment will be described with reference to the flowchart shown in FIG. In step 11, the distribution width of the luminance digital value is obtained. In the present embodiment, the difference between the maximum value and the minimum value of the luminance digital value is obtained as the distribution width, but is not limited thereto.
For example, in the histogram, a luminance digital value having a frequency of about 0% to 10% from the maximum value of the luminance digital value, a luminance digital value having a frequency of about 0% to 10% from the minimum value,
May be the difference.

In step 12, the exposure amount at the time of photographing is determined based on the distribution width of the luminance digital value. Specifically, it is determined using a map of the exposure amount at the time of shooting with respect to the distribution width of the luminance digital value as shown in FIG. That is, in the luminance histogram under the predetermined exposure amount condition at the time of the preliminary imaging, when the distribution width of the luminance digital value is large as shown in FIG. 6, the high luminance region is usually saturated in many cases. The amount is made smaller than a predetermined exposure amount to reduce the size of the high brightness region. Also, as shown in FIG. 7, when the distribution width of the luminance digital value is small, the exposure amount is made larger than a predetermined exposure amount, so that the distribution width of the luminance digital value is enlarged to increase the contrast of the main subject. Is determined in the manner described above.

In step 13, based on the determined exposure amount at the time of photographing, a luminance histogram at the exposure amount is created. Here, the brightness histogram is calculated based on the magnitude relationship between the newly determined exposure amount at the time of shooting and the exposure amount at the time of preliminary imaging, for example, based on the ratio of the two, using the brightness histogram created at step 1. This makes it possible to estimate and obtain the luminance value for each pixel under the exposure condition at the time of shooting. However, preliminary imaging is performed again under the same exposure condition as the exposure amount at the time of actual shooting determined at step 12 ( For example, half-pressing of the shutter is performed in two stages), and it can be created based on the luminance data at that time. Here, when the difference between the maximum value and the minimum value of the luminance at the time of preliminary photographing is large as shown in FIG. 5, the luminance histogram when the exposure amount at the time of photographing is small is as shown in FIG. The luminance histogram can be reduced when the frequency of the luminance region can be reduced, and when the difference between the maximum value and the minimum value of the luminance at the time of preliminary photographing is small as shown in FIG. As shown in FIG. 9, the difference between the maximum value and the minimum value of the luminance increases, and the high-frequency region shifts toward the high luminance region.

In step 14, a gradation characteristic is determined based on the new luminance distribution state. More specifically, as shown in FIG. 10 (corresponding to FIG. 8) and FIG. 11 (corresponding to FIG. 9), the 8-bit gradation characteristic of a straight line or a curve is used to make it difficult for the high luminance region to be saturated. That is, the saturation in the high luminance region is reduced using the straight line or the curve. In determining the gradation characteristics, the main subject can be determined to have appropriate brightness in relation to the exposure amount at the time of shooting. For example, since there is a high probability that a luminance region having a high distribution frequency in the luminance histogram is a main subject, it is necessary to determine and correct the gradation characteristics so that the average luminance of the luminance region becomes a reference luminance value. it can. The average brightness is
For example, "median", "cumulative histogram (ac
There is a specific frequency value in the cumulated histogram).

In this manner, by determining an appropriate exposure amount and gradation characteristics, saturation in a high-luminance area can be reduced, and a white image can be prevented from being formed, and an appropriate S / N ratio can be obtained.
The ratio can be obtained, and the image quality can be improved. The amount of noise includes a signal amount and a fixed amount. For a fixed amount noise, as the signal value increases, the S / N ratio improves.
To increase the signal value, increase the exposure. This effect occurs especially in low contrast images. In a high-contrast image, the S / N ratio deteriorates as much as the exposure is reduced, but highlight skipping is prevented.

Since the main subject is often photographed at the center of the image, as shown in FIG. 12, the average value of the luminance at the center of the image under the exposure condition at the time of photographing is calculated. By determining and correcting the gradation characteristics so that the average value becomes the reference luminance value, the main subject can be set to appropriate brightness. Alternatively, the average luminance of the entire image may be calculated as in a general AE, and the exposure amount and the gradation characteristic may be determined so that the average luminance becomes the reference luminance. Specifically, the exposure amount at the time of photographing is determined first in the same manner as described above, and the average luminance is determined while determining the gradation characteristics in the high-luminance region so that the high-luminance region is unlikely to be saturated under the exposure amount condition. It is possible to adopt a configuration in which the gradation characteristics of the remaining portion are determined so as to have the reference luminance.

Next, a second embodiment will be described. In this embodiment, when determining the gradation characteristic based on the luminance distribution state in step 14 in the first embodiment,
It is characterized in that a gradation characteristic different from that of the first embodiment is determined. Specifically, when the luminance difference or the contrast is small, the exposure amount is set to be relatively large in the present embodiment as in step 13 of the first embodiment. The gradation characteristic is determined so as not to be converted to brightness but to be brighter than the standard.

In this way, when the subject is a reflective object such as a printed matter, the white background of the document as the subject can be made closer to white, and a natural image can be obtained. Specifically, first, the maximum value X is detected from image data having a distribution of luminance digital values such as the luminance histogram in FIG. At this time, the detection position can be determined in advance within a frequency range of several percent from the maximum value of X. Next, FIG.
As shown in (1), the curve of the gradation characteristic is determined so that the obtained X becomes a substantially maximum output.

Specifically, the gain is changed according to the following equation with respect to a curve having a predetermined standard characteristic, so that the curve has a steep slope. Formula 1: Gain = 1023 / value X Further, in the vicinity of the high luminance portion, it is preferable to perform a smoothing process (moving average) in order to smooth the curve of the gradation characteristic. That is, the curve of the gradation characteristic is set in advance as a curve of the gradation characteristic, and the curve of the gradation characteristic is formed by the gain adjustment and the smoothing process under the above-mentioned predetermined condition.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a block diagram showing a hardware configuration of the still video camera according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing an exposure amount and gradation characteristic determination process in the embodiment.

FIG. 4 is a flowchart showing a detailed process of determining a gradation characteristic process according to the first embodiment;

FIG. 5 is a map for determining an exposure amount at the time of shooting with respect to a difference in luminance.

FIG. 6 is a luminance histogram in a case where a luminance difference under an exposure amount condition at the time of preliminary imaging is large.

FIG. 7 is a luminance histogram when the luminance difference is small.

FIG. 8 is a luminance histogram under the exposure amount condition at the time of shooting corresponding to FIG. 6;

9 is a luminance histogram corresponding to FIG. 6 under an exposure amount condition at the time of photographing.

FIG. 10 is a diagram showing gradation characteristics determined in correspondence with FIG. 8;

FIG. 11 is a diagram showing a gradation characteristic determined corresponding to FIG. 9;

FIG. 12 is a diagram for explaining a case where a gradation characteristic is determined by setting a central portion of an image as a region where a main subject exists.

FIG. 13 is a diagram illustrating gradation characteristics according to the second embodiment of the present invention.

[Explanation of symbols]

 104 CCD 106 A / D conversion circuit 107 process circuit 110 main CPU 111 memory card 113 output circuit 125 CCD drive circuit

Claims (22)

[Claims] 1. A luminance distribution state of an image is detected based on an image signal captured by an image sensor under a predetermined condition, and an exposure amount and a gradation characteristic are determined in association with each other based on the luminance distribution state of the image. A method for controlling an electronic camera. 2. The method according to claim 1, wherein the image signal is corrected based on the determined exposure amount and gradation characteristics to obtain a second image signal. 3. The method according to claim 1, wherein when determining the exposure amount and the gradation characteristic, the exposure amount is determined based on a luminance distribution state, and the gradation characteristic is determined based on the determined exposure amount. The method for controlling an electronic camera according to claim 1. 4. The method according to claim 1, wherein when the luminance difference in the luminance distribution state of the image is large, the exposure amount is determined to be small, and when the luminance difference is small, the exposure amount is determined to be large. Item 4. The control method for an electronic camera according to Item 3. 5. The luminance distribution state is a histogram,
The magnitude of the luminance distribution is A% from the maximum luminance of the image signal.
And the difference or ratio between the luminance of the frequency of the image signal and the luminance of B% from the minimum luminance of the image signal (where 0 ≦ A ≦ 10 and 0 ≦
B ≦ 10), according to any one of claims 1 to 4,
6. A control method for an electronic camera according to any one of the above. 6. A control method for an electronic camera according to claim 4, wherein when the luminance distribution is small, a gradation characteristic such that a gain is larger than a reference gain is determined. 7. A method for determining a tone characteristic, wherein a gain is larger than a reference or a reference gain when a luminance distribution is small, and a gradation characteristic is such that the gain is less than or equal to the reference gain. 6. The control method for an electronic camera according to claim 4, wherein both the tone characteristics and the tone characteristics can be set. 8. An exposure amount and a gradation characteristic are determined based on a luminance distribution state of the image so that a luminance region having a high frequency becomes a reference luminance. 7
The control method of an electronic camera according to any one of the above. 9. The electronic device according to claim 1, wherein the exposure amount and the gradation characteristic are determined so that the luminance at the center of the image becomes the reference luminance. Camera control method. 10. The electronic device according to claim 1, wherein the exposure amount and the gradation characteristic are determined such that the average luminance of the entire image becomes a reference luminance. Camera control method. 11. The method according to claim 1, wherein a gradation characteristic is determined based on a luminance distribution state of an image captured again using the determined exposure amount. 3. The control method for an electronic camera according to claim 1. 12. A luminance distribution state detecting means for detecting a luminance distribution state of an image based on an image signal picked up by an image pickup element under a predetermined condition, and an exposure amount determining means for determining an exposure amount based on the luminance distribution state. A control device for an electronic camera, comprising: a gradation characteristic determining unit that determines a gradation characteristic according to the exposure amount. 13. The electronic camera control device according to claim 12, wherein the image signal is corrected based on the determined exposure amount and gradation characteristics to obtain a second image signal. . 14. The exposure amount determining means and the gradation characteristic determining means determine an exposure amount based on a luminance distribution state in determining the exposure amount and the gradation characteristic, and determine the exposure amount based on the determined exposure amount. 14. The control device for an electronic camera according to claim 12, wherein the tone characteristic is determined by performing the following. 15. The exposure amount determination means determines the exposure amount to be small when the difference in luminance in the luminance distribution state of the image is large, and determines the exposure amount to be large when the difference in luminance is small. 15. The control device for an electronic camera according to claim 14, wherein: 16. The luminance distribution state is a histogram,
The magnitude of the luminance distribution is A% from the maximum luminance of the image signal.
And the difference or ratio between the luminance of the frequency of the image signal and the luminance of B% from the minimum luminance of the image signal (where 0 ≦ A ≦ 10 and 0 ≦
B ≦ 10) any one of claims 12 to 15, characterized in that:
A control device for an electronic camera according to any one of claims 1 to 3. 17. The method according to claim 15, wherein the gradation characteristic determining means determines a gradation characteristic such that a gain becomes larger than a reference gain when the luminance distribution is small. The control device for an electronic camera according to claim 1. 18. The image processing apparatus according to claim 18, wherein said gradation characteristic determining means determines a gradation characteristic such that a gain is larger than a reference gain when a luminance distribution is small. 17. The control device for an electronic camera according to claim 15, wherein both of the following gradation characteristics can be set. 19. The exposure amount determining unit and the gradation characteristic determining unit determine an exposure amount and a gradation characteristic based on a luminance distribution state of the image such that a luminance region having a high frequency becomes a reference luminance. 19. The control device for an electronic camera according to claim 12, wherein: 20. The exposure amount determining means and the gradation characteristic determining means, wherein a luminance at a central portion of the image is a reference luminance.
An exposure amount and a gradation characteristic are determined.
The control device for an electronic camera according to any one of claims 12 to 18. 21. The exposure amount determining means and the gradation characteristic determining means determine an exposure amount and a gradation characteristic such that an average luminance of the entire image becomes a reference luminance. The control device for an electronic camera according to any one of claims 12 to 18. 22. A method according to claim 12, wherein said gradation characteristic determining means determines a gradation characteristic based on a luminance distribution state of an image captured again using said determined exposure amount.
22. The control device for an electronic camera according to claim 21.