JP2007025129A - Exposure setting method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure setting method and an exposure setting device capable of preventing a photographing error caused by camera shake and subject shake with simple constitution. <P>SOLUTION: In the exposure setting method for setting sensitivity, diaphragm value and shutter speed based on an EV value obtained by performing photometry, the shutter speed higher than camera shake limit shutter speed by predetermined steps is provided as lower limit shutter speed. The sensitivity, the diaphragm value and the shutter speed are set so that the shutter speed may be always equal to or above the lower limit shutter speed. When the sensitivity and the diaphragm value attain a set limit, the shutter speed is set to be lower than the lower limit shutter speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure setting method and apparatus, and more particularly to an exposure setting method and apparatus for a digital camera that reduces camera shake and subject blur at the time of shooting.

  If camera shake occurs during shooting, there is a drawback that the image is blurred and a blurred image is shot. For this reason, an increasing number of digital cameras have a camera shake correction function.

Conventional camera shake correction mechanisms include a lens shift system that translates a part of the photographic optical system to compensate for camera shake, or a camera that translates the image sensor to cancel camera shake. An image sensor shift method for correction is known.
JP 2005-128092 A

  However, when a camera-shake correction mechanism of a lens shift system or an image sensor shift system is mounted on a digital camera, there are disadvantages that the configuration of the digital camera is complicated and large, and the cost is high. In addition, it is possible to prevent shooting mistakes due to camera shake, but there is a drawback in that it is impossible to prevent subject blurring caused by shooting mistakes caused by moving subjects.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exposure setting method and apparatus that can prevent a photographing error due to camera shake and subject blur with a simple configuration.

  According to a first aspect of the present invention, there is provided an exposure setting method for setting a sensitivity, an aperture value, and a shutter speed based on a photometric value obtained by photometry in order to achieve the above object. When the shutter speed is specified as the lower limit shutter speed, the sensitivity, the aperture value, and the shutter speed are set so that the shutter speed is always equal to or higher than the lower limit shutter speed. An exposure setting method is provided, wherein a shutter speed is set slower than the lower limit shutter speed.

  According to the first aspect of the present invention, the shutter speed is maintained at or above the lower limit shutter speed until the sensitivity and aperture setting limits are reached. As a result, camera shake and subject blur can be effectively suppressed, and shooting errors can be prevented.

  In order to achieve the above object, the invention according to claim 2 sets the aperture value and the shutter speed so that the shutter speed is always equal to or higher than the lower limit shutter speed in a state where the sensitivity is constant, and the aperture value is The sensitivity is increased when the set limit is reached, and the shutter speed is set to be equal to or higher than the lower limit shutter speed, and when the sensitivity reaches the set limit value, the shutter speed is set slower than the lower limit shutter speed. The exposure setting method according to 1 is provided.

  According to the invention of claim 2, first, the aperture value and the shutter speed are set so that the shutter speed becomes equal to or higher than the lower limit shutter speed in a state where the sensitivity is constant. When the aperture value reaches the setting limit, the sensitivity is increased and the shutter speed is set to be equal to or higher than the lower limit shutter speed. As a result, it is possible to prevent photographing errors due to camera shake and subject blur.

  In order to achieve the above object, the invention according to claim 3 sets the sensitivity, the aperture value, and the shutter speed by the exposure setting method according to claim 1 or 2 when the shooting mode for blurring reduction is set. When set and set to normal mode, the sensitivity, aperture value, and shutter speed are set so that the shutter speed is always equal to or higher than the camera shake limit shutter speed, and the sensitivity and aperture value reach the set limit values. Then, the exposure setting method according to claim 1 or 2, wherein a shutter speed is set slower than the camera shake limit shutter speed.

  According to the third aspect of the present invention, when the normal mode is set, the shutter speed is maintained at or above the camera shake limit shutter speed, and when the shooting mode for reducing blur is set, the shutter speed is set at or above the lower limit shutter speed. Maintained. Thereby, it becomes possible to select a shooting method according to the shooting purpose. That is, if the normal mode is selected, it is possible to suppress a decrease in image quality due to increased sensitivity, and if a shooting mode for reducing blur is selected, it is possible to prevent shooting errors due to camera shake and subject blur.

  According to a fourth aspect of the present invention, there is provided an exposure setting device for setting a sensitivity, an aperture value, and a shutter speed based on a photometric value obtained by photometry in order to achieve the above object. The storage means for storing the infinitely fast shutter speed as the lower limit shutter speed, and the sensitivity, aperture value, and shutter speed are set so that the shutter speed is always equal to or higher than the lower limit shutter speed, and the sensitivity and aperture value are at the setting limits. An exposure setting device comprising: an exposure setting unit that sets a shutter speed slower than the lower limit shutter speed when reaching the shutter speed.

  According to the fourth aspect of the invention, the shutter speed is maintained at or above the lower limit shutter speed until the sensitivity and aperture setting limits are reached. As a result, camera shake and subject blur can be effectively suppressed, and shooting errors can be prevented.

  According to a fifth aspect of the present invention, in order to achieve the above object, the exposure setting means sets the aperture value and the shutter speed so that the shutter speed is always equal to or higher than the lower limit shutter speed in a state where sensitivity is constant. When the aperture value reaches the set limit, increase the sensitivity and set the shutter speed to be equal to or higher than the lower limit shutter speed. When the sensitivity reaches the set limit value, set the shutter speed slower than the lower limit shutter speed. An exposure setting device according to claim 4 is provided.

  According to the fifth aspect of the invention, first, the aperture value and the shutter speed are set so that the shutter speed becomes equal to or higher than the lower limit shutter speed in a state where the sensitivity is constant. When the aperture value reaches the setting limit, the sensitivity is increased and the shutter speed is set to be equal to or higher than the lower limit shutter speed. As a result, it is possible to prevent photographing errors due to camera shake and subject blur.

  In order to achieve the above object, the invention according to claim 6 has a switching means for switching to a normal mode as a photographing mode, and when the mode is switched to the normal mode, the exposure setting means always has a shutter speed of the hand. The sensitivity, aperture value, and shutter speed are set so as to be equal to or higher than the blur limit shutter speed, and when the sensitivity and aperture value reach the set limits, the shutter speed is set slower than the camera shake limit shutter speed. An exposure setting device according to claim 4 or 5 is provided.

  According to the sixth aspect of the present invention, when the shooting mode is set to the normal mode, the shutter speed is maintained at or above the camera shake limit shutter speed. Thereby, it becomes possible to select a shooting method according to the shooting purpose. That is, if the normal mode is selected, it is possible to suppress a decrease in image quality due to increased sensitivity, and if another mode is selected, it is possible to prevent shooting errors due to camera shake and subject blur.

  According to the exposure setting method and apparatus of the present invention, it is possible to effectively prevent photographing errors due to camera shake and subject blur with a simple configuration.

  The best mode for carrying out an exposure setting method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the configuration of a digital camera to which the present invention is applied. As shown in the figure, the digital camera 10 of the present embodiment includes a photographing optical system 12, an image sensor 14, a timing generator (TG) 16, an analog signal processing unit 18, an A / D converter 20, and an image input controller 22. , Digital signal processing unit 24, encoder 28, image display unit 30, compression / decompression processing unit 32, media controller 34, storage medium 36, AE detection unit 38, AF detection unit 40, CPU 42, ROM 44, RAM 46, flash ROM 48, operation It consists of part 50 etc.

  The overall operation of the digital camera 10 is comprehensively controlled by the CPU 42, and the CPU 42 controls each unit of the digital camera 10 according to a predetermined program based on an input from the operation unit 50.

  In addition to the program executed by the CPU 42, the ROM 44 stores data necessary for various controls such as a program diagram. The CPU 42 develops the program stored in the ROM 44 in the RAM 46, and executes various processes while using the RAM 46 as a working memory. The flash ROM 48 stores various setting information relating to the operation of the digital camera 10 such as user setting information.

  The photographing optical system 12 includes a zoom lens 12z, a focus lens 12f, and a diaphragm (for example, iris diaphragm) 12i, and is operated by being driven by a zoom motor 60z, a focus motor 60f, and an iris motor 60i, respectively. That is, the zoom lens 12z is driven by the zoom motor 60z to move back and forth on the photographing optical axis, thereby changing the focal length. The focus lens 12f is driven by the focus motor 60f to move back and forth on the photographic optical axis, thereby changing the imaging position. In addition, the aperture 12i is driven by the iris motor 60i so that the opening amount changes stepwise, thereby changing the aperture value. The CPU 42 controls the driving of the zoom motor 60z, the focus motor 60f, and the iris motor 60i via the zoom motor driver 62z, the focus motor driver 62f, and the iris motor driver 62i, and performs operations of the zoom lens 12z, the focus lens 12f, and the aperture 12i. Control.

  The image sensor 14 is composed of a color CCD having a predetermined color filter array (for example, a Bayer array). Light incident on the light receiving surface of the image sensor 14 via the photographing optical system 12 is converted into signal charges in an amount corresponding to the amount of incident light by the photodiodes arranged on the light receiving surface. The signal charges accumulated in each photodiode are read according to the timing signal applied from the timing generator (TG) 16 and sequentially output from the image sensor 14 as a voltage signal (image signal).

  The image pickup device 14 includes a shutter gate and a shutter drain, and by applying a shutter gate pulse to the shutter gate, signal charges accumulated in each photodiode can be swept out to the shutter drain. Yes. The CPU 42 controls the charge accumulation time (shutter speed) of signal charges accumulated in each photodiode by controlling the application of the shutter gate pulse to the shutter gate via the TG 16 (so-called electronic shutter function).

  The analog signal processing unit 18 performs correlated double sampling processing and amplifies the image signals sequentially output from the image sensor 14. The A / D converter 20 converts the analog image signal output from the analog signal processing unit 18 into a digital image signal.

  The image input controller 22 includes a buffer memory having a predetermined capacity, accumulates one frame of the image signal output from the A / D converter 20, and stores it in the RAM 46.

  The digital signal processing unit 24 includes a synchronization circuit, a gamma correction circuit, a contour correction circuit, a luminance / color difference signal generation circuit, and the like, processes the image signal stored in the RAM 46 in accordance with a command from the CPU 42, and outputs the luminance signal and color difference signal A YUV signal consisting of

  When a through image is displayed on the image display unit 30, images are continuously captured by the image sensor 14, and the obtained image signals are continuously processed to generate a YUV signal. The generated YUV signal is applied to the encoder 28 via the RAM 46, converted into a signal format for display, and output to the image display unit 30. As a result, a through image is displayed on the image display unit 30.

  When an image is recorded, an image is picked up by the image pickup device 14 in accordance with a shooting command from the operation unit 50, and the obtained image signal is processed to generate a YUV signal. The generated YUV signal is added to the compression / decompression processing unit 32, converted into predetermined compressed image data (for example, JPEG), and then stored in the storage medium 36 via the media controller 34.

  The compressed image data stored in the storage medium 36 is read from the storage medium 36 in accordance with a reproduction command, converted into an uncompressed YUV signal by the compression / expansion processing unit 32, and then an image display unit via the encoder 28. 30 is output. As a result, the image recorded in the storage medium 36 is reproduced and displayed on the image display unit 30.

  The AE detection unit 38 calculates a physical quantity necessary for AE control from the input image signal in accordance with a command from the CPU 42. For example, as a physical quantity necessary for AE control, one screen is divided into a plurality of areas (for example, 16 × 16), and an integrated value of R, G, and B image signals is calculated for each divided area. The CPU 42 detects the brightness of the subject based on the integrated value obtained from the AE detector 38 to obtain a photometric value (EV value), and sets the exposure at the time of photographing based on the obtained EV value. This exposure setting method will be described in detail later.

  The AF detection unit 40 calculates a physical quantity necessary for AF control from the input image signal in accordance with a command from the CPU 42. In the digital camera 10 of the present embodiment, it is assumed that AF control is performed based on the contrast of the image, and the AF detection unit 40 calculates a focus evaluation value indicating the sharpness of the image from the input image signal. The CPU 42 controls the movement of the focus lens 12f by driving the focus motor 60f via the focus motor driver 62f so that the focus evaluation value calculated by the AF detection unit 40 is maximized.

  The digital camera 10 of the present embodiment is configured as described above.

  Next, an exposure setting method in the digital camera 10 of the present embodiment will be described. As described above, in the digital camera 10 of the present embodiment, the brightness of the subject is detected to obtain the EV value, and the exposure is set based on the obtained EV value.

  At this time, in the digital camera 10 of the present embodiment, the shutter speed is always set to be equal to or higher than the specified shutter speed (lower limit shutter speed) and the sensitivity and aperture value are set in order to prevent shooting errors due to camera shake and subject blur. When the limit is reached, the shutter speed is set slower than the lower limit shutter speed.

  Here, the lower limit shutter speed is a shutter speed set to a value that is a predetermined speed faster than the camera shake limit shutter speed, and is set to a shutter speed that is, for example, three stages faster than the camera shake limit shutter speed.

  The camera shake limit shutter speed generally depends on the focal length (35 mm film equivalent), and 1 / focal length [second] is defined. For example, when the focal length is 60 mm in terms of 35 mm film, 1/60 second is the camera shake limit shutter speed.

  It may be set uniformly without depending on the focal length. For example, 1/60 seconds may be uniformly set as the camera shake limit shutter speed.

  FIG. 2 is a diagram showing an example of a program diagram used in the digital camera 10 of the present embodiment, and shows a program diagram at a focal length of 45 mm (35 mm film equivalent).

  When the focal length is 45 mm, the camera shake limit shutter speed is 1/45 seconds, and the lower limit shutter speed is 1/360 seconds, which is three steps faster than that.

  Therefore, the sensitivity, aperture value, and shutter speed are set so that the shutter speed is always faster than 1/360 seconds. When the aperture value and sensitivity reach the set limits, the shutter speed is set slower than 1/360 seconds. Is done.

  Here, in the digital camera 10 of the present embodiment, ISO200, ISO400, ISO800, and ISO1600 can be set as sensitivity, and F2.8, F4, F5.6, F8, and F11 can be set as aperture values. The limit of sensitivity is ISO 1600, and the limit of aperture value is F2.8. Therefore, the shutter speed is maintained at the lower limit shutter speed (1/360 seconds) until the sensitivity ISO1600 and the aperture value F2.8 are reached, and when the sensitivity ISO1600 and the aperture value F2.8 are reached, the shutter speed is lower than the lower limit shutter speed. Is set too late.

  In the case of the program diagram shown in FIG. 2, in the range of EV18 to EV11.5, the sensitivity is constant (ISO 200) and the aperture value is changed stepwise to maintain the shutter speed at or above the lower limit shutter speed.

  Since the aperture value reaches the set limit (F2.8) at EV11.5, in the range of EV8.5 to EV11.5, the aperture value is constant (F2.8), and the sensitivity is changed stepwise. The shutter speed is maintained above the lower limit shutter speed.

  Since the sensitivity reaches the setting limit (ISO 1600) at EV 8.5, the sensitivity and the aperture value are constant in the range of EV 8.5 or less, and only the shutter speed is changed to set the exposure. In this case, the shutter speed is set below the lower limit shutter speed.

  In this way, by setting the shutter speed to be as high as possible or less than the lower limit shutter speed, it is possible to always ensure a high shutter speed and effectively suppress camera shake and subject blur.

  In this case, in order to keep the shutter speed equal to or higher than the lower limit shutter speed, first, the sensitivity is fixed and the aperture value is changed stepwise to keep the shutter speed higher than the lower limit shutter speed and the aperture value is set. When the limit is reached, the sensitivity is changed stepwise to keep the shutter speed above the lower limit shutter speed.

  Actual photographing is performed as follows. First, the S1 ON signal is input from the operation unit 50 to the CPU 42 by half-pressing the shutter button. In response to the input of the S1 ON signal input from the operation unit 50, the CPU 42 executes AE and AF processing. That is, as AE processing, an image signal for photometry is taken from the image sensor 14 and applied to the AE detection unit 38. The AE detector 38 calculates an integrated value from the input image signal and outputs the integrated value to the CPU 42. The CPU 42 calculates an EV value based on the integrated value obtained from the AE detector 38, and sets the exposure according to the above program diagram.

  Further, the CPU 42 captures an AF image signal from the image sensor 14 and adds it to the AF detection unit 40 as an AF process. The AF detection unit 40 calculates a focus evaluation value from the input image signal and outputs it to the CPU 42. The CPU 42 controls the drive of the focus motor 60f so that the focus evaluation value obtained from the AF detection unit 40 is maximized, and focuses on the main subject.

  Thereafter, when the shutter button is fully pressed, an S2 ON signal is input from the operation unit 50 to the CPU 42. In response to the S2 ON signal input from the operation unit, the CPU 42 performs image shooting and recording processing (when the shutter button is pressed halfway again, AE and AF processing are executed again). That is, an image signal for recording is taken from the image sensor 14 and added to the digital signal processing unit 24. The digital signal processing unit 24 performs necessary signal processing on the input image signal to create a YUV signal. The created YUV signal is compressed by the compression / decompression processing unit 32 and recorded in the storage medium 36 via the media controller 34. The image is photographed and recorded in the storage medium 36 through the series of steps described above.

  FIG. 3 is a flowchart showing a processing procedure of another exposure setting method for maintaining the shutter speed equal to or higher than the lower limit shutter speed.

  In this method, first, an EV value is obtained by photometry (step S10), and it is determined whether or not the obtained EV value is smaller than a limit value (step S11). This limit value is set as a value that can maintain the shutter speed equal to or higher than the lower limit shutter speed by changing the aperture value under the set sensitivity, and is set for each sensitivity. For example, as shown in FIG. 2, the sensitivity is set to EV11.5 under ISO200, EV10.5 under ISO400, EV9.5 under ISO800, and EV8.5 under ISO1600 (however, the lower limit) When the shutter speed is 1/360 seconds).

  When the EV value obtained by photometry is larger than the limit value in the currently set sensitivity, the shutter speed can be set to be equal to or higher than the lower limit shutter speed, so the shutter speed is set to a shutter speed faster than the lower limit shutter speed ( Step S12). For example, since the lower limit shutter speed is 1/360 seconds, it is set around 1/500 seconds. Then, the aperture value is determined under the set shutter speed (step S13).

  On the other hand, if the EV value obtained by photometry is smaller than the limit value in the currently set sensitivity, the shutter speed cannot be set higher than the lower limit shutter speed, so the sensitivity is increased. In this case, since the sensitivity also has a setting limit, it is determined whether or not the current setting sensitivity has reached the setting limit (step S14). If the result of this determination is that the sensitivity has not reached the set limit, the sensitivity is further increased (step S15). When the sensitivity is further increased, the limit value also changes. Therefore, the EV value obtained by photometry is again compared with the new limit value to determine whether the EV value is smaller than the limit value (step S16).

  When the EV value obtained by photometry is larger than the new limit value, the shutter speed can be set to be equal to or higher than the lower limit shutter speed, so the shutter speed is set to a shutter speed faster than the lower limit shutter speed (step S12) and set. The aperture value is determined under the shutter speed thus set (step S13).

  On the other hand, if the EV value obtained by photometry is smaller than the limit value, the shutter speed cannot be set equal to or higher than the lower limit shutter speed, so the process returns to step S14 to determine whether the sensitivity can be increased. That is, it is determined whether the sensitivity has reached the set limit.

  If the sensitivity has reached the set limit, neither the sensitivity nor the aperture value can be changed. Therefore, the normal shutter speed is set (step S17), and the aperture value is determined under the set shutter speed (step S13). .

  As described above, even in the case of this example, the shutter speed can be set to be equal to or higher than the lower limit shutter speed as much as possible, so that camera shake and subject blur can be effectively suppressed.

  Next, a second embodiment of the exposure setting method according to the present invention will be described.

  In the exposure setting method of the first embodiment, the camera speed and subject blur are prevented by maintaining the shutter speed at the lower limit shutter speed or higher. However, if the shutter speed is maintained at the lower limit shutter speed or higher, There is a problem that the image quality deteriorates due to the increased sensitivity.

  Therefore, in the second embodiment, as the exposure setting method, a normal shooting mode and a blur reduction shooting mode for the purpose of blur reduction can be selected, and when the blur reduction shooting mode is selected. Only when the shutter speed is maintained above the lower shutter speed and the normal shooting mode is selected, exposure control is performed so as to maintain the shutter speed above the camera shake limit shutter speed.

  FIG. 4 is a diagram showing an example of a program diagram used in the normal photographing mode, and shows a program diagram at a focal length of 45 mm (35 mm film equivalent). In this case, the camera shake limit shutter speed is 1/45 seconds.

  As shown in FIG. 4, in the range of EV18 to EV8.5, the sensitivity is constant (ISO 200), and the aperture value is changed stepwise to maintain the shutter speed at or above the camera shake limit shutter speed.

  Since the aperture value reaches the setting limit (F2.8) at EV8.5, in the range of EV5.5 to EV8.5, the aperture value is kept constant (F2.8), and the sensitivity is changed stepwise. Keep the shutter speed at or above the camera shake limit shutter speed.

  Since the sensitivity reaches the setting limit (ISO 1600) at EV 5.5, the sensitivity and the aperture value are constant in the range of EV 5.5 or less, and the exposure is set by changing only the shutter speed. In this case, the shutter speed is set below the camera shake limit shutter speed.

  In the blur reduction shooting mode, exposure is set using a program diagram as shown in FIG. 2, and the shutter speed is maintained at or above the camera shake limit shutter speed.

  Switching between the blur reduction shooting mode and the normal shooting mode is performed by the operation unit 50. For example, a dedicated switch is installed in the camera body, and the mode is switched by setting the switch. In addition, the mode may be set by a GUI using the image display unit 30 or may be automatically switched in conjunction with a specific shooting mode. Alternatively, the attachment to a tripod may be detected and switched automatically. That is, when the camera body is attached to a tripod, there is no possibility of camera shake, so the normal shooting mode may be automatically set.

  FIG. 5 is a flowchart showing a processing procedure of another exposure setting method in the normal photographing mode.

  In this method, first, an EV value is obtained by photometry (step S20), and it is determined whether or not the obtained EV value is smaller than a camera shake limit value (step S21). This camera shake limit value is set as a value that can maintain the shutter speed equal to or higher than the camera shake limit shutter speed by changing the aperture value under the set sensitivity, and is set for each sensitivity. For example, as shown in FIG. 4, the sensitivity is set to EV 8.5 under ISO 200, EV 7.5 under ISO 400, EV 6.5 under ISO 800, and EV 5.5 under ISO 1600. (When the blur limit shutter speed is 1/45 seconds).

  When the EV value obtained by photometry is larger than the camera shake limit value at the currently set sensitivity, the shutter speed can be set to be equal to or higher than the camera shake limit shutter speed, so the shutter speed is faster than the camera shake limit shutter speed. The shutter speed is set (step S22). Then, the aperture value is determined under the set shutter speed (step S23).

  On the other hand, if the EV value obtained by photometry is smaller than the limit value in the currently set sensitivity, the shutter speed cannot be set higher than the lower limit shutter speed, so the sensitivity is increased. In this case, since the sensitivity also has a setting limit, it is determined whether or not the current setting sensitivity has reached the setting limit (step S24). If the result of this determination is that the sensitivity has not reached the set limit, the sensitivity is increased by one step (step S25). When the sensitivity is further increased, the camera shake limit value also changes. Therefore, the EV value obtained by photometry is again compared with the new camera shake limit value to determine whether or not the EV value is smaller than the camera shake limit value (step). S26).

  If the EV value obtained by photometry is larger than the camera shake limit value, the shutter speed can be set to be equal to or higher than the camera shake limit shutter speed, so the shutter speed is set to a shutter speed faster than the camera shake limit shutter speed (step S22) An aperture value is determined under the set shutter speed (step S23).

  On the other hand, if the EV value obtained by photometry is smaller than the camera shake limit value, the shutter speed cannot be set higher than the camera shake limit shutter speed, so the process returns to step S24 to determine whether the sensitivity can be increased. That is, it is determined whether the sensitivity has reached the set limit.

  If the sensitivity has reached the set limit, neither the sensitivity nor the aperture value can be changed. Therefore, a normal shutter speed is set (step S27), and the aperture value is determined under the set shutter speed (step S23). .

  Also by the above method, the shutter speed can be set to be equal to or higher than the camera shake limit shutter speed as much as possible.

  FIG. 6 is a flowchart showing a processing procedure of another exposure setting method in the normal photographing mode, and shows an exposure setting method when the aperture is constant.

  First, an EV value is obtained by photometry (step S30), and an aperture value is set (step S31). The aperture value may be set by the user or automatically according to other conditions.

Next, determine the shutter speed S ₁ of the provisional based from a set aperture value EV value (step S32). Shutter speed _{S 1} obtained is, determines whether fast or not than shake limit shutter speed _{S 0} (step S33). Shutter speed S ₁ of the provisional, faster than shake limit shutter speed S ₀ sets the shutter speed of the temporary to the shutter speed of the photographing (step S34).

On the other hand, the shutter speed S ₁ of the provisional, if slower than shake limit shutter speed S ₀ determines whether sensitivity has reached the set limit (step S35). If the sensitivity has not reached the set limit, the sensitivity is increased by one step (step S36), and the temporary shutter speed is set again under the changed sensitivity (step S32). Then, the shutter speed _{S 1} is, determines whether fast or not than shake limit shutter speed _{S 0} (step S33).

On the other hand, when the sensitivity has reached the set limit in step S35, it is impossible to increase the sensitivity, setting the shutter speed S ₁ of the temporary to the shutter speed of the photographing (step S34).

  Also by the above method, the shutter speed can be set to be equal to or higher than the camera shake limit shutter speed as much as possible.

  FIG. 7 is a flowchart showing a processing procedure of another exposure setting method in the blur reduction photographing mode, and shows an exposure setting method when the aperture is constant.

  First, an EV value is obtained by photometry (step S40), and an aperture value is set (step S41). The aperture value may be set by the user or automatically according to other conditions.

  Next, it is determined whether or not the obtained EV value is smaller than a limit value (step S42). This limit value is set as a value that can maintain the shutter speed equal to or higher than the lower limit shutter speed under the set sensitivity and aperture value, and is set for each sensitivity and aperture value.

  When the EV value obtained by photometry is larger than the currently set sensitivity and aperture limit values, the shutter speed can be set to be equal to or higher than the lower limit shutter speed, so the shutter speed is set to a shutter speed faster than the lower limit shutter speed. Set (step S43).

  On the other hand, if the EV value obtained by photometry is smaller than the currently set sensitivity and aperture value limit values, the shutter speed cannot be set higher than the lower limit shutter speed, so the sensitivity is increased. In this case, since the sensitivity also has a set limit, it is determined whether or not the current set sensitivity has reached the set limit (step S44). If the sensitivity has not reached the set limit, the sensitivity is further increased (step S45). ). When the sensitivity is further increased, the limit value also changes. Therefore, the EV value obtained by photometry is again compared with the new limit value to determine whether the EV value is smaller than the limit value (step S46). If the EV value obtained by photometry is larger than the newly set limit value, the shutter speed can be set to be equal to or higher than the lower limit shutter speed, so the shutter speed is set to a shutter speed faster than the lower limit shutter speed (step S43).

  On the other hand, if the EV value obtained by photometry is smaller than the limit value, the shutter speed cannot be set higher than the lower limit shutter speed, so the process returns to step S44 to determine whether the sensitivity can be increased. That is, it is determined whether the sensitivity has reached the set limit.

  If the sensitivity has reached the set limit, the sensitivity cannot be changed, so a normal shutter speed is set (step S47).

  As described above, even in the case of this example, the shutter speed can be set to be equal to or higher than the lower limit shutter speed as much as possible, so that camera shake and subject blur can be effectively suppressed. This method can also be used in the exposure setting method of the first embodiment described above.

  As described above, according to the exposure setting method of the present embodiment, the normal shooting mode that can prevent image quality deterioration due to increased sensitivity, and the blur reduction mode that can prevent camera shake and subject blur by securing a fast shutter speed. Can be selected, it is possible to perform shooting according to the application.

  In the digital camera 10 of the above-described embodiment, the EV value is obtained based on the image signal obtained from the image sensor 14, but the method for obtaining the EV value is not limited to this, and other methods are available. The EV value may be obtained using a photometric sensor or the like.

  In this embodiment, the case where the present invention is applied to a digital camera has been described as an example. However, the application of the present invention is not limited to this, and a function of performing still image shooting using an imaging element is described. It can be applied to general equipment.

Block diagram showing the configuration of the digital camera Diagram showing an example of program diagram Flow chart showing processing procedure of exposure setting method Example of program diagram used in normal shooting mode Flowchart showing processing procedure of exposure setting method in normal shooting mode Flowchart showing processing procedure of exposure setting method in normal shooting mode The flowchart which shows the processing procedure of the exposure setting method at the time of blur reduction photographing mode

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 12 ... Shooting optical system, 14 ... Image sensor, 16 ... Timing generator (TG), 18 ... Analog signal processing part, 20 ... A / D converter, 22 ... Image input controller, 24 ... Digital signal processing 28: Encoder, 30 ... Image display unit, 32 ... Compression / decompression processing unit, 34 ... Media controller, 36 ... Storage medium, 38 ... AE detection unit, 40 ... AF detection unit, 42 ... CPU, 44 ... ROM, 46 ... RAM, 48 ... flash ROM, 50 ... operation unit

Claims (6)

In an exposure setting method for setting sensitivity, aperture value, and shutter speed based on a photometric value obtained by photometry,
A shutter speed that is a predetermined step faster than the camera shake limit shutter speed is defined as the lower limit shutter speed,
Set the sensitivity, aperture value, and shutter speed so that the shutter speed is always equal to or higher than the lower limit shutter speed.
An exposure setting method comprising: setting a shutter speed slower than the lower limit shutter speed when the sensitivity and the aperture value reach a setting limit. Set the aperture value and shutter speed so that the shutter speed is always equal to or higher than the lower limit shutter speed with the sensitivity kept constant.
When the aperture value reaches the set limit, increase the sensitivity and set the shutter speed to be above the lower limit shutter speed,
2. The exposure setting method according to claim 1, wherein when the sensitivity reaches a set limit value, a shutter speed is set slower than the lower limit shutter speed. When the shooting mode is set to reduce blur,
The sensitivity, aperture value, and shutter speed are set by the exposure setting method according to claim 1 or 2,
When set to normal mode,
Set the sensitivity, aperture value, and shutter speed so that the shutter speed is always above the camera shake limit shutter speed,
3. The exposure setting method according to claim 1, wherein when the sensitivity and the aperture value reach a set limit value, the shutter speed is set slower than the camera shake limit shutter speed. In an exposure setting device that sets sensitivity, aperture value, and shutter speed based on a photometric value obtained by photometry,
Storage means for storing a shutter speed that is a predetermined speed higher than the camera shake limit shutter speed as a lower limit shutter speed;
The sensitivity, aperture value, and shutter speed are set so that the shutter speed is always equal to or higher than the lower limit shutter speed, and when the sensitivity and aperture value reach the set limits, the shutter speed is set slower than the lower limit shutter speed. Exposure setting means;
An exposure setting device comprising:   The exposure setting means sets an aperture value and a shutter speed so that the shutter speed is always equal to or higher than the lower limit shutter speed with a constant sensitivity, and when the aperture value reaches a setting limit, the sensitivity is increased. 5. The exposure setting apparatus according to claim 4, wherein a shutter speed is set to be equal to or higher than the lower limit shutter speed, and when the sensitivity reaches a set limit value, the shutter speed is set to be slower than the lower limit shutter speed.   A switching unit that switches to a normal mode as a photographing mode is provided, and when the mode is switched to the normal mode, the exposure setting unit has a sensitivity, an aperture value, and a shutter so that the shutter speed is always equal to or higher than the camera shake limit shutter speed. 6. The exposure setting apparatus according to claim 4, wherein a speed is set, and when the sensitivity and the aperture value reach a setting limit, the shutter speed is set slower than the camera shake limit shutter speed.

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