JP2008193635A - Electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately suppress a photographed image of an electronic camera from being blurred, and image quality from being reduced. <P>SOLUTION: An electronic camera 1 includes luminance detection means 22, 23, 11 for detecting lightness; an imaging device 22 for picking up a subject image; and an exposure control means 11 for improving exposure sensitivity before prolonging an exposure time to camera shake limit seconds when controlling exposure by changing either the exposure time or the exposure sensitivity of the imaging device 22 in accordance with the lightness detected by the luminance detection means 22, 23, 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic camera.

  A technique for eliminating the influence of camera shake during shooting is known (see Patent Document 1). In the prior art, a camera shake prevention program diagram is used instead of the standard program diagram.

JP 2005-286790 A

  According to the camera shake prevention program diagram, since a relatively high shutter speed is set compared to the standard program diagram, a relatively high sensitivity is set compared to the standard program diagram. When the sensitivity is increased uniformly, noise increases as the sensitivity is increased, and there is a problem in that the image quality is degraded.

(1) An electronic camera according to the present invention includes a brightness detection unit that detects brightness, an image sensor that captures a subject image, and exposure time and exposure sensitivity of the image sensor according to the brightness detected by the brightness detection unit. In the case where exposure is controlled by changing either one of them, exposure control means for increasing the exposure sensitivity before extending the exposure time to the camera shake limit time is provided.
(2) In the electronic camera according to claim 1, it is preferable that the exposure control means enhances the exposure sensitivity when the exposure time is short even if the exposure time is extended by one step shorter than the camera shake limit time.
(3) In the electronic camera according to claim 2, when the exposure control means increases the exposure sensitivity to the first sensitivity and the exposure is insufficient, the exposure time is set to the camera shake limit second or from the camera shake limit second. It is preferable to make it longer.
(4) In the electronic camera of the third aspect, it is preferable that the exposure control means further increases the exposure sensitivity from the first sensitivity before extending the exposure time to a subject blur limit second longer than the camera shake limit second.
(5) In the electronic camera according to claim 4, the exposure control means may change the exposure sensitivity from the first sensitivity when the exposure time is short even if the exposure time is increased by one step shorter than the subject blur limit time. It is preferable to increase.
(6) In the electronic camera according to claim 5, the exposure control means sets the exposure time to a subject blur limit when exposure is insufficient even when the exposure sensitivity is increased from the first sensitivity to the second sensitivity lower than the sensitivity limit value. It is preferable that the time is longer than the second or longer than the subject blur limit second.
(7) In the electronic camera according to (6), it is preferable that the exposure control means further increases the exposure sensitivity from the second sensitivity when the exposure is insufficient even if the exposure time is extended to the limit value.
(8) In the electronic camera according to (3), it is preferable that the exposure control means maintains the exposure sensitivity at the first sensitivity when the illumination device that illuminates the subject is allowed to emit light.
(9) In the electronic camera according to claim 8, the exposure control means preferably makes the exposure time longer than the subject blur limit second when the exposure is insufficient while the exposure sensitivity is maintained at the first sensitivity. .
(10) An electronic camera according to the present invention includes a brightness detection unit that detects brightness, an image sensor that captures a subject image, and exposure time and exposure sensitivity of the image sensor according to the brightness detected by the brightness detection unit. In the case where exposure is controlled by changing either one of them, exposure control means for increasing exposure sensitivity before extending the exposure time to subject blur limit seconds is provided.
(11) In the electronic camera according to claim 10, it is preferable that the exposure control means enhances the exposure sensitivity when the exposure is insufficient even if the exposure time is extended to a second shorter than the subject blur limit second. .
(12) In the electronic camera according to claim 11, when the exposure time is one second shorter than the subject blur limit time, the exposure control means lowers the range in which the exposure sensitivity is increased from the first sensitivity to the sensitivity limit value. It is preferable to limit to the second sensitivity.

  With the electronic camera according to the present invention, it is possible to appropriately suppress blurring of captured images and deterioration of image quality.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining a main configuration of an electronic camera 1 according to an embodiment of the present invention. The electronic camera 1 is controlled by the main CPU 11.

  The photographing lens 21 forms a subject image on the imaging surface of the imaging element 22. The imaging element 22 is configured by a CCD image sensor or the like, captures a subject image on the imaging surface, and outputs an imaging signal to the imaging circuit 23.

  The ND (Neutral Density) filter 20 is a dimming member that attenuates transmitted light by a predetermined amount (for example, two stages of apex values). The ND filter 20 is driven back and forth in a direction orthogonal to the optical axis of the photographing lens 21 by the drive mechanism 19. When the ND filter 20 is driven and inserted into the optical path of the subject light, the amount of light incident on the image sensor 22 is limited by the ND filter 20. On the other hand, when the ND filter 20 is driven and withdrawn from the optical path of the subject light, the amount of light incident on the image sensor 22 is not limited. The drive mechanism 19 performs forward / backward drive with respect to the ND filter 20 in accordance with an instruction from the main CPU 11.

  The imaging circuit 23 changes the imaging sensitivity (exposure sensitivity) in a predetermined range (for example, equivalent to ISO 50 to ISO 1000) in a predetermined step in response to a sensitivity change instruction from the main CPU 11. The imaging sensitivity refers to a controlled amount that changes the detection sensitivity of charges accumulated in the imaging element 22 or the amplification gain of an amplifier circuit (not shown). The imaging sensitivity value is represented by a corresponding ISO sensitivity value. The imaging circuit 23 further converts the analog imaging signal into digital data using the built-in A / D conversion circuit in response to an imaging instruction from the main CPU 11.

  The AF device 18 detects the focus adjustment state of the photographic lens 21 according to an instruction from the main CPU 11, and drives a focus lens (not shown) constituting the photographic lens 21 forward and backward in the optical axis direction according to the detection result. The focus detection information detected by the AF device 18 can be used as shooting distance information indicating the distance to the main subject as a focus detection target.

  The main CPU 11 inputs a signal output from each block, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block. The image processing circuit 12 is configured as an ASIC, for example, and performs image processing on the digital image signal input from the imaging circuit 23. The image processing includes, for example, contour enhancement, color temperature adjustment (white balance adjustment) processing, and format conversion processing for an image signal.

  The image compression circuit 13 performs image compression processing at a predetermined compression ratio on the image signal processed by the image processing circuit 12 by the JPEG method. The display image creation circuit 15 creates display data for displaying the captured image on the liquid crystal monitor 16.

  The recording medium 30 includes a memory card that can be attached to and detached from the electronic camera 1. The recording medium 30 records captured image data and an image file including the information in accordance with an instruction from the main CPU 11. The image file recorded on the recording medium 30 can be read by an instruction from the main CPU 11.

  The buffer memory 14 temporarily stores data before and after image processing and during image processing, stores an image file before being recorded on the recording medium 30, and stores an image file read from the recording medium 30. Used for.

  The operation member 17 includes various buttons and switches of the electronic camera 1 and outputs an operation signal corresponding to the operation content of each operation member to the main CPU 11 such as a release button pressing operation and a function setting switch switching operation.

  The light emitting device 24 emits light with a predetermined light amount according to an instruction from the main CPU 11 to illuminate the subject. The light emitting device 24 transmits light emission preparation information (such as charging information) to the main CPU 11, and the main CPU 11 transmits information indicating the light emission timing (light emission instruction) and the light emission amount to the light emitting device 24. When the use of the light emitting device 24 is permitted, the electronic camera 1 sets shooting conditions so that the light emitting device 24 emits light when it is determined that the subject is dark at the time of shooting. When the use of the light emitting device 24 is prohibited, the electronic camera sets shooting conditions so that the light emitting device 24 does not emit light.

<Shooting operation>
The main CPU 11 starts photometry when an operation signal indicating a half-press operation of the release button is input from the operation member 17. Specifically, the imaging device 22 performs imaging for photometry, and the brightness information of the object scene is acquired from the signal value of the imaging signal output after charge accumulation. The main CPU 11 further performs an exposure calculation based on the brightness information and determines an exposure condition.

  When an operation signal indicating a full press of the release button is input from the operation member 17 following the half-press operation signal, the main CPU 11 starts a photographing operation. Specifically, the image pickup device 22 is made to accumulate charge for photographing under the determined exposure conditions. The image pickup circuit 23 performs the above-described signal processing on the image pickup signal output from the image pickup element 22 after accumulating charge for photographing.

  The image processing circuit 12 outputs the image data subjected to the signal processing to the display image creation circuit 15, so that the photographed image is displayed on the liquid crystal monitor 16. The image data compressed by the image compression circuit 13 is recorded on the recording medium 30. When recording in the uncompressed state is instructed to the recording medium 30 by operating the operation member 17, the recording is performed on the recording medium 30 without performing the compression processing in the image compression circuit 13. Yes.

  Since the present embodiment has a feature in determining exposure conditions at the time of photographing, this point will be further described mainly. The main CPU 11 of the electronic camera 1 set to the program auto mode automatically determines the shutter speed, the aperture value, and the sensitivity according to the brightness of the object scene. The aperture value of the electronic camera 1 is alternatively selected from two values obtained by inserting and removing the ND filter 20 with respect to the optical path. The shutter speed corresponds to the charge accumulation time (exposure time) of the image sensor 22, and the charge accumulation time of the image sensor 22 is controlled by a so-called electronic shutter system.

  FIG. 2 is a program diagram illustrating exposure control when the light emission prohibition of the light emitting device 24 is set. In FIG. 2, the vertical axis represents the subject brightness (brightness of the object scene), and the higher the brightness is, the lower the brightness is. The horizontal axis (upper) represents the determined shutter speed, and the right side is faster and the left side is slower. The horizontal axis (lower) represents the determined imaging sensitivity, with the higher sensitivity toward the right side and the lower sensitivity toward the left side. A solid line represents an example of control when the zoom lens of the photographing lens 21 is moved to the wide angle side (wide end), and a broken line represents control when the zoom lens of the photographing lens 21 is moved to the telephoto side (tele end). An example is shown. The reason why the control is changed between the wide angle side and the telephoto side is that the open F value of the photographing lens 21 is different between the wide angle side and the telephoto side. The one-dot chain line will be described later.

<When light emission of the light emitting device is prohibited>
1. Control at Wide End Hereinafter, the control at the wide angle side will be described.
(Luminance range 1) B ≧ 11
The main CPU 11 sends an instruction to the drive mechanism 19 if the brightness is B11 or higher as a result of photometry performed in response to the half-pressing operation of the release button, and moves the ND filter 20 on the optical path of the subject light guided to the image sensor 22. Let As a result, the amount of light incident on the image sensor 22 is reduced by two steps in terms of apex value compared to when the ND filter 20 is moved out of the optical path (at the time of full aperture).

  The main CPU 11 further sends an instruction to the imaging circuit 23 to set the imaging sensitivity to an initial value. The initial sensitivity value in this embodiment is S0. The initial sensitivity value S0 is preferably a value on the low sensitivity side (not necessarily the control limit value) in the imaging sensitivity control range. The main CPU 11 calculates the shutter speed so that proper exposure is obtained in a state where the ND filter 20 is inserted on the optical path (small aperture), and obtains a control value indicated by a solid line.

  Specifically, the imaging sensitivity is maintained at the initial value S0 on the higher brightness side than B11, and the shutter speed changes from T1 ′ to the control limit value on the higher brightness side (the shutter speed is the higher speed side) according to the brightness. To determine the control exposure. The shutter speed T1 ′ is a value programmed in advance, and is a speed corresponding to B11 at the time of sensitivity S0 and small aperture.

(Luminance range 2) 11> B ≧ 8
The main CPU 11 sends an instruction to the drive mechanism 19 if the luminance is less than B11 as a result of photometry performed in response to the half-pressing operation of the release button, and moves the ND filter 20 outside the optical path of the subject light guided to the image sensor 22. Let As a result, the amount of light incident on the image sensor 22 is increased by two steps in apex value compared to when the ND filter 20 is moved on the optical path (at the time of a small aperture).

  The main CPU 11 calculates the shutter speed so that proper exposure is obtained in a state where the ND filter 20 is retracted out of the optical path (aperture is opened), and obtains a control value indicated by a solid line. Specifically, the imaging sensitivity is maintained at the initial value S0 in the range of B8 to B11, and the shutter speed is changed according to the brightness from T1 to the shutter speed T0 on the high luminance side (the shutter speed is the high speed side). To determine the control exposure.

  The shutter speed T1 is a value programmed in advance, and is a value one step higher than a speed corresponding to an exposure time (for example, indicated by 1 / focal length) called a camera shake limit second. The shutter speed T0 is a speed corresponding to B11 when the sensitivity S0 and the aperture are opened.

(Luminance range 3) 8> B ≧ 6
In the luminance range 3, the main CPU 11 calculates the imaging sensitivity so that proper exposure is obtained, and obtains a control value indicated by a solid line. Specifically, the shutter speed is maintained at T1 in the range of B6 to B8, and the imaging sensitivity is set according to the brightness from the initial value S0 to a predetermined value S1 in the control range on the low luminance side (high sensitivity side as imaging sensitivity). By changing the control exposure, the control exposure is determined.

(Luminance range 4) 6> B ≧ 4
In the luminance range 4, the main CPU 11 calculates the shutter speed so that proper exposure is obtained, and obtains a control value indicated by a solid line. Specifically, by maintaining the imaging sensitivity at S1 in the range of B4 to B6 and changing the shutter speed from T2 to the shutter speed T1 on the high luminance side (the shutter speed is the high speed side) according to the brightness, Determine the control exposure.

  The shutter speed T2 is a value programmed in advance, and is a value one step higher than the speed corresponding to the exposure time called the so-called subject blur limit time.

(Luminance range 5) 4> B ≧ 3
In the luminance range 5, the main CPU 11 calculates the imaging sensitivity so as to obtain an appropriate exposure, and obtains a control value indicated by a solid line. Specifically, the shutter speed is maintained at T2 in the range of B3 to B4, and the imaging sensitivity changes from S1 to a predetermined value S2 within the control range on the low luminance side (high sensitivity side as imaging sensitivity) according to the brightness. To determine the control exposure.

(Luminance range 6) 3> B ≧ 0
In the luminance range 6, the main CPU 11 calculates the shutter speed so that proper exposure is obtained, and obtains a control value indicated by a solid line. Specifically, the imaging sensitivity is maintained at S2 in the range of B0 to B3, and the shutter speed is changed according to the brightness from T3 to the shutter speed T2 on the high luminance side (the shutter speed is the high speed side). Determine the control exposure. The shutter speed T3 is a control limit value on the low speed side.

(Luminance range 7) 0> B
In the luminance range 7, the main CPU 11 calculates the imaging sensitivity so as to approach the appropriate exposure, and obtains a control value indicated by a solid line. Specifically, the shutter speed is maintained at T3 below B0, and the imaging sensitivity is changed according to the brightness from S2 to the control limit value S3 on the low luminance side (high sensitivity side as imaging sensitivity), thereby controlling exposure. To decide.

2. Tele-end control Hereinafter, tele-side control will be described.
(Luminance range 1 ′) B ≧ 12
The main CPU 11 sends an instruction to the drive mechanism 19 if the luminance is B12 or higher as a result of photometry performed in response to the half-press operation of the release button, and moves the ND filter 20 on the optical path of the subject light guided to the image sensor 22. Let

  The main CPU 11 sets the imaging sensitivity to the initial value S0, calculates the shutter speed so that proper exposure can be obtained in a state where the ND filter 20 is inserted on the optical path (small aperture), and a control value indicated by a broken line Get.

  Specifically, the imaging sensitivity is maintained at the initial value S0 on the higher brightness side than B12, and the shutter speed changes from T1 ′ to the control limit value on the higher brightness side (the shutter speed is the higher speed side) according to the brightness. To determine the control exposure. The shutter speed T1 ′ is a value programmed in advance, and is a speed corresponding to B12 at the time of sensitivity S0 and small aperture.

(Luminance range 2 ′) 12> B ≧ 10
The main CPU 11 sends an instruction to the drive mechanism 19 if the luminance is less than B12 as a result of photometry performed in response to the half-press operation of the release button, and moves the ND filter 20 out of the optical path of the subject light guided to the image sensor 22. Let

  The main CPU 11 maintains the imaging sensitivity at the initial value S0 in the range of B10 to B12, and changes the shutter speed from T1 ′ to the shutter speed T0 on the high luminance side (the shutter speed is the high speed side) according to the brightness. Thus, the control exposure is determined.

  The shutter speed T1 ′ is a value programmed in advance, and is set to a value one step higher than a speed corresponding to an exposure time referred to as a so-called camera shake limit time. The reason why the camera shake limit speed at the telephoto end is different from the camera shake limit speed at the wide-angle end is that the focal length is different between the telephoto end and the wide-angle end.

(Luminance range 3 ′) 10> B ≧ 8
In the luminance range 3 ′, the main CPU 11 calculates imaging sensitivity so as to obtain appropriate exposure, and obtains a control value indicated by a broken line. Specifically, the shutter speed is maintained at T1 ′ in the range of B8 to B10, and the imaging sensitivity is increased from the initial value S0 to a predetermined value S1 within a control range on the low luminance side (high sensitivity side as imaging sensitivity). The control exposure is determined by changing it accordingly.

(Luminance range 4 ′) 8> B ≧ 5
In the luminance range 4 ′, the main CPU 11 calculates the shutter speed so that proper exposure is obtained, and obtains a control value indicated by a broken line. Specifically, the imaging sensitivity is maintained at S1 in the range of B5 to B8, and the shutter speed is changed according to the brightness from T2 to the shutter speed T1 ′ on the high luminance side (the shutter speed is the high speed side). Determine the control exposure.

  The shutter speed T2 is a value programmed in advance, and is the same speed as the control at the wide angle end.

(Luminance range 5 ′) 5> B ≧ 4
The main CPU 11 maintains the shutter speed at T2 in the range of B4 to B5, and changes the imaging sensitivity from S1 to a predetermined value S2 within the control range on the low luminance side (high sensitivity side as imaging sensitivity). By doing so, the control exposure indicated by the broken line is determined.

(Luminance range 6 ′) 4> B ≧ 1
The main CPU 11 maintains the imaging sensitivity in the above-described S2 in the range of B1 to B4, and changes the shutter speed from T3 to the shutter speed T2 on the high luminance side (the shutter speed is the high speed side) according to the brightness. A control exposure indicated by a broken line is determined.

(Luminance range 7 ') 1> B
The main CPU 11 maintains the shutter speed at T3 below B1, and changes the imaging sensitivity from S2 to the control limit value S3 on the low luminance side (high sensitivity side as imaging sensitivity) according to the brightness. Determine the control exposure shown.

(Luminance range 2A) 10> B ≧ 9
When the electronic camera 1 includes an image stabilization mechanism for suppressing camera shake, and the image stabilization mechanism is turned on, the following luminance range 2A may be performed. The main CPU 11 maintains the imaging sensitivity at the initial value S0 in the range of B9 to B10, and changes the shutter speed from T1 to the shutter speed T0 on the high luminance side (the high speed side as the shutter speed) according to the brightness. Thus, the control exposure indicated by the alternate long and short dash line is determined.

  The shutter speed T1 is a value programmed in advance, and is the same speed as the control at the wide angle end. When the anti-vibration mechanism operates, the influence of camera shake is suppressed, and therefore the camera shake limit speed common to that at the wide angle is used even during telephoto. In this case, the luminance range 3 ′ is controlled in a range of 9> B ≧ 7.

<When the light emitting device is allowed to emit light>
FIG. 3 is a program diagram illustrating exposure control when the light emission permission of the light emitting device 24 is set. In this embodiment, so-called slow sync control is performed. In FIG. 3, the vertical axis represents subject brightness (brightness of the object scene), the horizontal axis (upper) represents the determined shutter speed, and the horizontal axis (lower) represents the determined imaging sensitivity. 2 and common. A solid line indicates a control example when the zoom lens of the photographing lens 21 is moved to the wide angle side (wide end), and a broken line indicates a case where the zoom lens of the photographing lens 21 is moved to the telephoto side (tele end). Each control example is shown. The alternate long and short dash line represents control when the vibration isolation mechanism is turned on at the telephoto end.

  The main CPU 11 causes the light emitting device 24 to emit light with a predetermined amount of light when shooting according to the control exposure shown in FIG. The predetermined amount of light is determined by causing the light emitting device to emit light with a small amount of light (referred to as pre-emission) before photographing. Specifically, the image sensor 22 performs light adjustment imaging at the time of pre-emission, and a light emission amount (main light emission amount) necessary at the time of photographing is determined using a signal value of an imaging signal output after charge accumulation. If the main subject is close to the electronic camera 1, a smaller amount of light emission is required than when the main subject is far away, and if the object is bright, a smaller amount of light emission is required than when it is dark. Therefore, the main CPU 11 calculates the light emission amount by comprehensively considering the distance information to the main subject, the subject luminance BV, and the imaging sensitivity.

The control illustrated in FIG. 3 and the control illustrated in FIG. 2 are different when the shutter speed is lower than the brightness T2 (the shutter speed is the lower speed side), so this difference will be mainly described.
1. Control at Wide End The points on the wide angle side that differ from FIG. 2 are as follows.
(Luminance range 4A) 4> B ≧ 2
In the luminance range 4A, the main CPU 11 calculates the shutter speed so that proper exposure is obtained, and obtains a control value indicated by a solid line. Specifically, by maintaining the imaging sensitivity at S1 in the range of B2 to B4 and changing the shutter speed from T4 to the shutter speed T2 on the high luminance side (the shutter speed is the high speed side) according to the brightness, Determine the control exposure. The shutter speed T4 is a speed corresponding to the sensitivity S1 and B2 when the aperture is opened.

(If a shortage of light emission is expected)
If the main CPU 11 does not obtain the proper exposure even if the shutter speed is changed to T4 with the imaging sensitivity S1 maintained, that is, if the main subject is dark even when the light emitting device 24 is fully lit (maximum light emission), the shutter The control exposure is determined by changing the imaging sensitivity from S1 to the control limit value S3 on the low luminance side (high sensitivity side as imaging sensitivity) so as to approach the appropriate exposure while maintaining the speed at T4.

2. Control at Tele End The telephoto side control differs from FIG. 2 as follows.
(Luminance range 4A ′) 5> B ≧ 3
In the luminance range 4A ′, the main CPU 11 calculates the shutter speed so that proper exposure is obtained, and obtains a control value indicated by a broken line. Specifically, by maintaining the imaging sensitivity at S1 in the range of B3 to B5, and changing the shutter speed from T4 to the shutter speed T2 on the high luminance side (the shutter speed is the high speed side) according to the brightness, Determine the control exposure.

(If a shortage of light emission is expected)
If the main CPU 11 does not obtain the proper exposure even if the shutter speed is changed to T4 with the imaging sensitivity S1 maintained, that is, if the main subject is dark even when the light emitting device 24 is fully lit (maximum light emission), the shutter The control exposure is determined by changing the imaging sensitivity from S1 to the control limit value S3 on the low luminance side (high sensitivity side as imaging sensitivity) so as to approach the appropriate exposure while maintaining the speed at T4.

According to the embodiment described above, the following operational effects can be obtained.
(1) The electronic camera 1 that controls either the shutter speed or the imaging sensitivity in accordance with the brightness can reduce the shutter speed to T1, which is one step higher than the speed corresponding to the exposure time called the camera shake limit time. When exposure is insufficient, the shutter speed T1 is maintained and the imaging sensitivity is set higher than the initial value S0. Since the shutter speed T1 has a margin of one stage until the camera shake limit time, it is possible to reliably suppress the occurrence of camera shake. Note that the value of T1 may be a value two steps faster than the speed corresponding to the camera shake limit second.

(2) The electronic camera 1 maintains the imaging sensitivity S1 and makes the shutter speed slower than T1 when the exposure is insufficient even when the imaging sensitivity is increased from S0 to S1. By limiting the imaging sensitivity to S1 lower than the limit value S3, noise superimposed on the imaging signal can be suppressed as compared with the case where the imaging sensitivity is higher than S1. That is, it is possible to suppress deterioration in image quality.

(3) The electronic camera 1 maintains the shutter speed T2 and maintains the image pickup sensitivity when the exposure is insufficient even if the shutter speed is delayed to T2 that is one step faster than the speed corresponding to the exposure time called the subject blur limit time. Was made higher than S1. Since the shutter speed T2 has a margin of one stage until the subject blur limit time, occurrence of subject blur can be reliably suppressed. Note that the value of T2 may be a value that is two steps faster than the speed corresponding to the subject blur limit time.

(4) When the exposure is insufficient even when the imaging sensitivity is increased from S1 to S2, the electronic camera 1 maintains the imaging sensitivity S2 and makes the shutter speed slower than T2. By limiting the imaging sensitivity to S2 lower than the limit value S3, noise superimposed on the imaging signal can be suppressed as compared with the case where the imaging sensitivity is higher than S2. That is, it is possible to suppress deterioration in image quality.

(5) The electronic camera 1 maintains the shutter speed T3 and makes the imaging sensitivity higher than S2 when the exposure is insufficient even if the shutter speed is reduced to the limit value T3. By making it possible to change the imaging sensitivity toward the limit value S3 when the minimum speed (longest time) is reached, it is possible to cope with shooting under darker conditions.

(6) The electronic camera 1 that is permitted to emit light from the light emitting device 24 maintains the shutter speed T2 and does not increase the imaging sensitivity than S1, but keeps the imaging speed S1 and the shutter speed slower than T2. did. Since the main subject is exposed during the time illuminated by the flash light from the light emitting device 24 (shorter than the shutter speed), even if the shutter time becomes longer than the subject blur limit time, the effect of the subject blur becomes a problem. It is difficult. By performing such slow sync photography, it is possible to suppress noise superimposed on the imaging signal during flash photography against a night scene.

(7) The electronic camera 1 that is allowed to emit light from the light emitting device 24 does not obtain proper exposure even if the shutter speed is decreased to T4 while maintaining the imaging sensitivity S1, and even if the light emitting device 24 is caused to emit maximum light. When the main subject is dark, the imaging speed can be changed from S1 to the limit value S3 while maintaining the shutter speed at T4. Thereby, it is possible to cope with shooting under dark conditions with a long shooting distance.

(Modification 1)
In the above description, the brightness information is obtained using the image pickup signal from the image pickup device 22, but a photometric sensor is provided separately from the image pickup device 22, and the brightness information is obtained using this sensor output. It may be.

(Modification 2)
The configuration of the AF device 18 is an AF method that acquires contrast information called a focus evaluation value using an image pickup signal from the image pickup element 22, and uses a light beam other than the transmitted light of the photographing lens 21 (so-called external light type AF). ). Moreover, even if it is configured with an active AF method that acquires focus evaluation information by projecting infrared light for focus detection, etc., it is configured with a passive AF method that acquires focus evaluation information without projecting infrared light or the like. May be.

(Modification 3)
The light emitting device 24 may be configured to use an external light emitting device in addition to the one built in the electronic camera 1.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

It is a block diagram explaining the principal part structure of the electronic camera which is one Embodiment of this invention. It is a figure which illustrates exposure control in case a light-emitting device is prohibited from light emission. It is a figure which illustrates exposure control when the light-emitting device is permitted to emit light.

Explanation of symbols

1 ... Electronic camera 11 ... Main CPU
17 ... Operation member 21 ... Shooting lens 22 ... Imaging element 24 ... Light emitting device

Claims (12)

Luminance detection means for detecting brightness;
An image sensor for capturing a subject image;
When the exposure is controlled by changing either the exposure time or the exposure sensitivity of the image sensor in accordance with the brightness detected by the brightness detection means, the exposure is performed before the exposure time is increased to the camera shake limit time. An electronic camera comprising exposure control means for increasing sensitivity. The electronic camera according to claim 1,
The electronic camera according to claim 1, wherein the exposure control means increases the exposure sensitivity when the exposure is insufficient even if the exposure time is extended to a second that is one step shorter than the camera shake limit time. The electronic camera according to claim 2,
The exposure control means is characterized in that, when the exposure is insufficient even when the exposure sensitivity is increased to the first sensitivity, the exposure time is set to the camera shake limit second or longer than the camera shake limit second. Electronic camera. The electronic camera according to claim 3.
The electronic camera according to claim 1, wherein the exposure control unit further increases the exposure sensitivity from the first sensitivity before extending the exposure time to a subject blur limit second longer than the camera shake limit second. The electronic camera according to claim 4,
The exposure control means increases the exposure sensitivity from the first sensitivity when the exposure is insufficient even if the exposure time is extended to a second shorter than the subject blur limit second by one step. camera. The electronic camera according to claim 5,
If the exposure is insufficient even if the exposure sensitivity is increased from the first sensitivity to a second sensitivity lower than the sensitivity limit value, the exposure control means sets the exposure time to the subject blur limit time or the subject An electronic camera that is longer than the blur limit second. The electronic camera according to claim 6.
The electronic camera according to claim 1, wherein the exposure control means further increases the exposure sensitivity from the second sensitivity when the exposure is insufficient even if the exposure time is extended to a limit value. The electronic camera according to claim 3.
The electronic camera according to claim 1, wherein the exposure control means maintains the exposure sensitivity at the first sensitivity when light emission of an illumination device that illuminates a subject is permitted. The electronic camera according to claim 8,
The electronic camera according to claim 1, wherein the exposure control means makes the exposure time longer than the subject blur limit time when the exposure is insufficient while maintaining the exposure sensitivity at the first sensitivity. Luminance detection means for detecting brightness;
An image sensor for capturing a subject image;
When the exposure is controlled by changing either the exposure time or the exposure sensitivity of the image sensor according to the brightness detected by the brightness detecting means, the exposure time is increased before the subject blur limit time is increased. An electronic camera comprising exposure control means for increasing exposure sensitivity. The electronic camera according to claim 10.
The electronic camera according to claim 1, wherein the exposure control means increases the exposure sensitivity when the exposure is insufficient even if the exposure time is extended to a second shorter than the subject blur limit second. The electronic camera according to claim 11,
The exposure control means limits the range for increasing the exposure sensitivity from the first sensitivity to the second sensitivity lower than the sensitivity limit value when the exposure time is one step shorter than the subject blur limit second. An electronic camera characterized by

Images