JP2006157526A - Electronic camera and controlling method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a photographed image look better in quality by allowing the size (the size of a printing paper or the like) of the image when viewed to be specified arbitrarily, setting a permissible blur (diameter of permissible circle of confusion) fitting to the specified size, and changing photographing conditions according to the permissible blur. <P>SOLUTION: An electronic camera comprises an imaging means 20 for photographing a subject under given photographing conditions to generate the image signal of the subject image, a size specifying means 21 for specifying the size of the image signal when the image is viewed, a calculating means 21 for calculating the diameter of permissible circle of confusion fitting to the size when the image is viewed, and a photographing conditions changing means 21 for changing the photographing conditions according to the diameter of permissible circle of confusion. The electronic camera changes the diameter of permissible circle of confusion such that it fits the size of the image when it is viewed, and also changes the photographing conditions according to the changed diameter of permissible circle of confusion, thus making it possible to avoid inappropriate diameter of permissible circle of confusion and to make the image look better in quality. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electronic camera such as a digital camera and a control method thereof.

  In general, in many electronic cameras such as digital cameras, adjustments such as focus (focus) and aperture are automated. For example, in the “autofocus camera” described in Patent Document 1, the depth of field is calculated based on the lens information and the distance measurement information, and the optimum AF suitable for the depth of field and the distance measurement information is calculated. (Autofocus) mode is selected. In the “depth-of-field display device” described in Patent Document 2, the depth of field is calculated from the distance, aperture value, and focal length of the subject of interest in the composition, and other subjects are set to the depth of field. The user is informed by the lamp display in the finder whether or not it is present. In the “shooting distance indication device” described in Patent Document 3, the depth of field is calculated from the focal length, distance measurement distance, and aperture value of the zoom lens, and is displayed as the length of the bar in the viewfinder.

Japanese Patent No. 3026589 JP-A-5-232371 JP-A-8-220419

  By the way, images taken with an electronic camera are visualized using various media (PC display, printing paper, etc.) and are finally used for viewing. Since the size of the image at the time of viewing is not taken into consideration at all, depending on the size of the viewing image, the image may appear out of focus.

  This is because the confirmation image at the time of shooting with an electronic camera is a small image that can be seen through a view window (viewfinder) or a small image that is projected on a monitor screen of several inches, but is finally used for viewing. The image is much larger than that, for example, in the case of printing paper, because it has various sizes such as business card and L size, the circle of confusion is enlarged especially in the case of a large paper size, This is because it may appear out of focus. Here, when the subject is focused, the “point” at the focus position appears on the CCD / CMOS screen as well, but the “point” at a location other than the focus position appears on the CCD / CMOS screen. Blurred and reflected in a “circle”. This “circle” is called a “circle of confusion”, and the allowable value of the circle of confusion that appears to be in focus is called “allowable circle of confusion” (or allowable blur).

  In view of this, the present invention allows an arbitrary size (printing paper size, etc.) for appreciating an image when an image of a subject is captured, and allows an allowable blur (allowable circle of confusion circle) suitable for the specified size. An object is to improve the image quality of an appreciation image by setting and changing the shooting condition according to the allowable blur.

The electronic camera according to claim 1, an imaging unit that shoots a subject under a predetermined shooting condition and generates an image signal of the subject image, a size designation unit that designates a viewing size of the image signal, and the viewing time It is characterized by comprising calculation means for calculating a permissible circle of confusion appropriate for the size, and photographing condition changing means for changing the photographing condition corresponding to the permissible circle of confusion.
The electronic camera according to claim 2 is the electronic camera according to claim 1, wherein the photographing condition is any one or all of an aperture, a focal length, a depth of field, an exposure, a hyperfocal distance, and a focal depth. It is characterized by that.
The electronic camera control method according to claim 3, an imaging step of shooting a subject under a predetermined shooting condition and generating an image signal of the subject image, a size specifying step of specifying a viewing size of the image signal, The method includes a calculation step of calculating an allowable confusion circle diameter suitable for the viewing size, and an imaging condition changing step of changing the imaging condition corresponding to the allowable confusion circle diameter.
The electronic camera control method according to claim 4 is the electronic camera control method according to claim 3, wherein the photographing condition is any one of an aperture, a focal length, a depth of field, an exposure, a hyperfocal distance, and a focal depth. Or it is characterized by being all of them.

In the present invention, when an image signal viewing size is specified, an allowable confusion circle diameter suitable for the viewing size is calculated, and the imaging condition of the image signal corresponds to the allowable confusion circle diameter. Be changed. Here, the imaging condition to be changed can be any one or all of an aperture, a focal length, a depth of field, an exposure, a hyperfocal distance, and a focal depth.
The permissible circle of confusion (or permissible blur) is the permissible value of a circle of confusion that appears to be in focus. This allowable circle of confusion has been set to a constant value regardless of the size at the time of viewing, such as the print paper size or display size, so the focus may have shifted depending on the size at the time of viewing. In the present invention, the permissible circle of confusion is changed in accordance with the size at the time of viewing, and the shooting conditions are changed according to the permissible circle of confusion after the change. This can be eliminated and the quality of the appreciation image can be improved.

  Embodiments of the present invention will be described below with reference to the drawings, taking application to a digital camera as an example. It should be noted that the specific details or examples in the following description and the illustrations of numerical values, character strings, and other symbols are only for reference in order to clarify the idea of the present invention, and the present invention may be used in whole or in part. Obviously, the idea of the invention is not limited. In addition, a well-known technique, a well-known procedure, a well-known architecture, a well-known circuit configuration, and the like (hereinafter, “well-known matter”) are not described in detail, but this is also to simplify the description. Not all or part of the matter is intentionally excluded. Such well-known matters are known to those skilled in the art at the time of filing of the present invention, and are naturally included in the following description.

  FIG. 1 is a front view and a rear view of the digital camera 1. In this figure, the digital camera 1 (electronic camera) as an example is not particularly limited, but a retractable lens barrel 3, a strobe light emission window 4, a finder front window 5 and a sound collecting hole are provided on the front surface of a box-shaped body 2. 6 and the like, and a power switch 7 and a shutter button 8 are arranged on the upper surface thereof, and further, a finder rear window 9, a shooting mode / playback mode switch 10, a zoom operation button 11, a menu button 12, The jog dial 13, the loudspeaker hole 14, the liquid crystal display 15, and the like are disposed, and in addition, a memory slot 17 having a lid 16 is disposed on the side surface thereof, and a removable storage medium (for example, a memory card 18) is disposed in the memory slot 17. Is configured to be inserted.

  FIG. 2 is an internal block diagram of the digital camera 1. In this figure, the digital camera 1 includes, for each function, an audio input system 19, an imaging system 20 (imaging means), a control system 21 (size designation means, calculation means, photographing condition changing means), an audio output system 22, and image data. It can be classified into an equal memory system 23, a display system 24, an operation system 25, and the like.

  Explaining each of these systems, the audio input system 19 is amplified by the microphone 26 disposed near the sound collection hole 6 on the front surface of the body, the amplifier 27 that amplifies the sound picked up by the microphone 26, and the amplifier 27. A / D converter 28 for converting the analog audio signal into a digital signal, and an audio memory 29 for temporarily storing the digitally converted audio signal.

  The imaging system 20 includes a photographic lens group 30 with a zoom function and an autofocus function housed in a lens barrel 3 in front of the body, and a subject image that has passed through the photographic lens group 30 in a two-dimensional image signal (here, An electronic image pickup unit 31 composed of a CCD, a CMOS, or the like to be converted into a square image signal having an aspect ratio of 1: 1, and necessary image processing such as gamma correction is performed on the image signal from the electronic image pickup unit 31. A video processing unit 32 and an image memory 33 for temporarily storing the image signal after the image processing are provided, a focus driving unit 34 for driving a focus mechanism (not shown) of the lens barrel 3, and the zoom mechanism. A zoom driving unit 35 for driving, a strobe light emitting unit 36 provided in the strobe light emitting window 4 on the front surface of the body, a strobe driving unit 37 for driving the strobe light emitting unit 36, and And a photographing control section 38 for controlling each unit (electronic imaging section 31, the image processing unit 32, the focus driving section 34, a zoom driving unit 35, flash driving unit 37).

  The control system 21 controls each of the above systems to control the operation of the digital camera 1 centrally, and a program memory 40 that stores various programs necessary for the operation of the control circuit 39 in a nonvolatile manner. A data memory 41 for storing various data necessary for the operation of the control circuit 39 in a non-volatile manner, and a print sheet information memory 42 for storing various types of print sheet information (see FIGS. 6 and 7) in advance are provided. .

  The audio output system 22 includes a D / A converter 43 that converts audio data appropriately output from the control circuit 39 into an analog audio signal, an amplifier 44 that amplifies the audio signal, and amplifies the amplified audio signal. For this purpose, a speaker 45 is provided near the loudspeaker hole 14 on the back of the body.

  The image data memory system 23 is a general-purpose encoding method for image data (still image data and moving image data) and audio data (for example, JPEG or a compatible format for still image data, moving image and audio data). A compression encoding / decompression decoding unit 46 that compresses (encodes) and decompresses (decodes) data in MPEG or a compatible format thereof, and an image that stores the encoded image data and audio data in a rewritable manner. & Audio memory medium (in the example shown, a memory card 18 inserted into the memory slot 17 on the side of the body).

  The display system 24 converts display data appropriately output from the control circuit 39 into a predetermined display format (display format adapted to the resolution of the liquid crystal display 15), and outputs signals from the display control unit 47. An image monitor (liquid crystal display 15) provided on the back of the body for display.

  The operation system 25 includes an operation input unit 48 including a shutter button 8 on the upper surface of the body, a shooting mode / playback mode switching switch 10 on the rear surface, a zoom operation button 11, a menu button 12, a jog dial 13, and the like. And an input circuit 49 for inputting an operation signal to the control circuit 39. The liquid crystal display 15 provided on the back of the body has a touch panel, and signals (signals such as touch coordinates) of the touch panel are also input to the control circuit 39 via the operation input unit 48 and the input circuit 49. Shall be.

  FIG. 3A is a diagram illustrating a display example of the liquid crystal display 15 when the shooting mode is selected. In this figure, a display screen 50 is a screen of the liquid crystal display 15 when the photographing mode / reproduction mode switching switch 10 on the back of the body is set to the “photographing mode” position. This display screen 50 displays a through image 51 (a monitor image for composition adjustment, etc.) accompanied by a movement from the imaging system 20, and various shooting information symbols and the like are superimposed and displayed around the through image 51. Yes. For example, in the illustrated example, the currently selected printing paper information 52 (“L” in the illustrated example) is displayed in the upper right corner. In addition, although it is set as the printing paper here, it is not limited to this. Any medium for visualizing and appreciating images may be used.

  FIG. 3B is a diagram illustrating a display example of the printing paper selection screen 53. The print paper selection screen 53 is displayed on the liquid crystal display 15 when a predetermined button operation is performed while the shooting mode is selected. In the illustrated example, “110 size” and “half size” are displayed. , “35 mm size”,..., “Business card format”,..., “L size” surrounded by a square frame is selected. When changing to a printing paper other than “L”, the user can press the OK button 54 after selecting the destination printing paper, or press the cancel button 55 to cancel the change.

  FIG. 4 is a diagram showing an operation flowchart of the control system 21. When this flowchart is started, first, the shooting mode / reproduction mode switching switch 10 is checked to determine whether or not the current mode is the “shooting mode” (step S10). If it is not “shooting mode”, other mode processing such as a playback mode is executed (step S11). If it is “shooting mode”, it is determined whether or not to change the printing paper (step S12). . This determination may be made, for example, based on whether or not the user's finger touches the print paper information 52 displayed in the upper right corner of the print paper selection screen 53 in FIG.

  When the printing paper is changed, that is, when the determination result in step S12 is “YES”, the printing paper selection screen 53 shown in FIG. The user is prompted to select a print sheet (steps S13 and S14). When the printing paper is changed, the image size or image quality mode (the resolution of the photographed image: for example, the finest of the highest resolution, the normal of the intermediate resolution, the low resolution) is changed according to the size of the printing paper after the change. Are set (step S15), and an allowable blur (allowable confusion circle diameter) δ is set according to the size of the printing paper (step S16).

  Next, after performing photometric processing and white balance processing (step S17), the focusing accuracy of AF processing is set according to the allowable circle of confusion circle δ set in step S16 (step S18). Next, the presence / absence of a zoom operation is determined (step S19). If the zoom operation has been performed, the zoom process is executed (step S20), and then according to the focusing accuracy set in step S18 above. AF (automatic focusing) processing is then executed (step S21).

  In AF processing, for example, a high frequency component is extracted from a captured image signal in an AF area such as a focus frame through a filter or the like, and the contrast level is determined from the magnitude of the amplitude of the luminance signal. It searches for a place with the highest amplitude and contrast, and controls to adjust the position of the focus lens.

  In general, the contrast is detected while driving the focus lens, and when the contrast gradually increases from a low contrast, the point before the decrease is determined as the peak when the contrast gradually increases. Then, AF (focusing) operation is performed by performing so-called hill-climbing control for stopping the driving of the focus lens.

  In this example, the focus position by the AF operation is controlled to be a more accurate focus position according to the set allowable confusion circle diameter δ. More specifically, the depth of focus within the depth of focus corresponding to the permissible circle of confusion δ, that is, the depth of field Z at this time (in focus) If the depth of focus corresponding to the range of distance on the subject side))) is Z ′, the depth of focus Z′≈ ± δ F = 2δ F (where δ is the allowable circle of confusion, F is an aperture value). Therefore, when the permissible circle of confusion δ is smaller so that the depth of focus Z ′ is Z ′ ≦ 2δF, the determination of focusing in the AF operation and the ending condition of the hill-climbing control are performed. However, the switching is performed using a higher frequency component in the signal in the AF area of the captured image or using a determination condition with a higher contrast value. Alternatively, control is performed so that the driving accuracy of the focus lens position to be hill-climbing controlled, the fineness (pitch) of the driving step, and the like are switched so as to be driven with higher accuracy or with finer steps.

  Then, a through image of the subject image is displayed on the liquid crystal display 15 (step S21), whether or not the shutter button 8 is depressed (release ON operation) or other key operations are determined (step S23), and other key operations are performed. If it is determined, the process corresponding to the key is executed. For example, if the menu button 12 is operated, the required menu display process is executed (step S24), and then the process returns to step S10 again, while the release ON operation is performed. Is determined, the photometric process and the white balance process are executed (step S25), and then the captured image or the extracted image in the selected composition frame area is compression encoded by the compression encoding / decompression decoding unit 46, The size, paper size, and shooting condition data are stored in the image memory (memory card 18) (step S26), and then re-entered. Returns to the step S10.

  FIG. 5 is a diagram illustrating a setting calculation example of the allowable blur (allowable confusion circle diameter) δ. In this figure, (a) is a calculation example when the print image is viewed from a clear viewing distance (25 cm), and (b) is a calculation example when the print image is viewed from a diagonal distance of the printing paper. That is, in the former (a), an allowable blur (allowable confusion circle diameter) δ is set based on the selected printing paper diagonal (S) and imaging device diagonal (Y), or the expression “δ = 250 × 0.00077 × Y / S ”. In the latter case (b), an allowable blur (allowable circle of confusion) δ is set based on the imaging device diagonal (Y), or the expression “δ = S × 0.00077 × Y / S = 0. “00077 × Y” is calculated. Here, the printing paper diagonal (S) is the length of the diagonal line of the selected printing paper (for example, 21.40 mm for 110 size, 30.00 mm for half size,...). In addition, the imaging device diagonal (Y) is the length of the diagonal line of the imaging surface of the electronic imaging unit 31 (for example, 11 mm for a 2/3 type CCD and 8 mm for a 1/2 type CCD). In the case of a 1/3 type CCD, it means 6 mm,.

  6 and 7 are diagrams showing examples of data tables 56 and 57 necessary for setting calculation of the allowable blur (allowable confusion circle diameter) δ. These data tables 56 and 57 are stored in the printing paper information memory 42. FIG. Pre-stored. The data table 56 in FIG. 6 is used for calculation when the print image is viewed from a clear vision distance (25 cm), and the data table 57 in FIG. 7 is used for calculation when the print image is viewed from the diagonal distance of the printing paper. These tables 56 and 57 are provided with a record for each paper size type ("110 size", "half size",...), And each record has a paper width dimension (W). Fields 56a and 57a, sheet longitudinal dimension (H) fields 56b and 57b, sheet diagonal length fields 56c and 57c, image sensor size conversion fields 56d and 57d, and the like are shown in FIG. The table 56 is provided with a permissible circle of confusion diameter field 56e when viewed from a clear visual distance (25 cm). In the data table 57 of FIG. 7, the permissible circle of confusion diameter field when viewed from a diagonal distance. 57e is provided.

  In general, the ability to distinguish small things with the human naked eye is said to be about 1 minute (1 ') in angle, but I saw something that changes continuously like a photograph. In such a case, the angle is slightly looser than that, and is about 2 to 3 minutes (2 'to 3'). In other words, it is said that human eyes cannot distinguish anything smaller than 2'-3 ', and those below 2'-3' are not seen to be blurred and appear sharp. ing. Therefore, when the photograph is viewed from the clear visual distance (25 cm) of the naked eye, a blur (0.15 to 0.22 mm) of about 250 mm × tan (2 ′) to 250 mm × tan (3 ′) It will be acceptable.

  On the other hand, there is a concept that it is natural to view a photograph from a distance corresponding to a diagonal dimension, for example, depending on its size. For example, a photographic paper with a diagonal of 27 cm (close to the clear viewing distance) can tolerate a blur of up to about 0.2 mm. Since the enlargement magnification is 6 times, the blur of 35 mm size is 0.2 ÷ 6 = 0.33 mm, and this value is the allowable blur size or allowable confusion of general 35 mm size (36 × 24 mm) film. It is adopted as a circle diameter. In this method, an allowable confusion circle diameter within a predetermined angle (2 ′ to 3 ′) may be used according to the size of the film or the image sensor regardless of the printing paper or the enlargement magnification, and it is convenient for conversion. Yes, not everyone prints only on eight-size paper. In this conversion method, the larger the printing paper and enlargement magnification, the greater the tolerance of blurring and blurring. Therefore, it may be inconvenient if the allowable blur is determined only by the viewing angle.

  In view of the above points, in the present embodiment, the print paper size can be arbitrarily selected according to the user's request during the shooting mode, and the image resolution and tolerance can be selected according to the selected print paper size. The size of the blur (allowable circle of confusion) is automatically set, and the AF processing and focusing accuracy are set according to the resolution of the image and the size of the blur (allowable circle of confusion). Therefore, the above inconveniences (when the paper size and enlargement magnification are large and when they are viewed at a close distance, the roughness and blur of the focus are conspicuous) are eliminated, and the image quality is improved by optimizing the degree of allowable blur of the printed image Can be improved.

  In the above embodiment, the resolution of the image and the size of the allowable blur (allowable circle of confusion) are automatically set according to the selected printing paper size, and the resolution of the image and the size of the allowable blur are also set. Although AF processing, focusing accuracy, etc. are set according to (allowable circle of confusion), it is not limited to this. For example, according to the selected printing paper size, the image resolution and the allowable blur size (allowable confusion circle diameter) are automatically set, and the allowable blur size (allowable confusion circle diameter) is set, You may make it perform automatic exposure (AE) imaging | photography with priority of depth of field, pan focus imaging | photography, etc.

  FIG. 8 and FIG. 9 are flowcharts showing operations when performing depth-of-field priority AE shooting, pan-focus shooting, and the like. When this flowchart is started, first, it is determined whether or not the “shooting mode” is set (step S30). If it is not the shooting mode, other mode processing such as a playback mode is executed (step S31). If it is the shooting mode, a required selection screen (see the printing paper selection screen 53 in FIG. 3B) is displayed on the liquid crystal. Displayed on the display 15 prompts the user to select (step S32), and sets the aspect ratio of the composition frame corresponding to the aspect ratio of the selected printing paper (step S33). Next, an image size or an image quality mode is set according to the size of the selected printing paper (step S34), and the vertical / horizontal pixel ratio of the composition frame displayed on the viewfinder is calculated from the set image size and the aspect ratio (step S35). ).

  Next, it is determined whether or not the printed image is viewed from the clear viewing distance (step S36). When the printed image is viewed from the clear viewing distance, an allowable confusion is obtained from the print paper diagonal (S) and the imaging size diagonal (Y). The circle diameter δ is set, or the equation “δ = 250 × 0.00077 × Y / S” is calculated (step S37). If not viewed from the clear viewing distance, it is determined whether to view from the paper diagonal distance (step S38). If viewed from the paper diagonal distance, the permissible circle of confusion from the imaging size diagonal (Y) is determined. The diameter δ is set or the equation “δ = S × 0.00077 × Y / S = 0.00077 × Y” is calculated (step S39). Further, if it is not viewed from the sheet diagonal distance, an arbitrary value is input to the allowable confusion circle diameter δ (step S40).

  In either case, the photometric process and the white balance (WB) process are executed (step S41), and the zoom process and the AF process are executed (step S42). Is detected (step S43), and it is determined whether or not to perform automatic exposure by pan focus (step S44).

When performing automatic exposure by pan focus, after setting the subject distance L to the hyperfocal distance L∞ (step S45), the focal length f set in step S43 and the step S37, step S39 or step Based on the permissible circle of confusion δ set in S40 and the hyperfocal distance L∞ set in step S45, the expression “F = f ² / (δ · L∞)” is executed to calculate the aperture value F. (Step S46).

If automatic exposure by pan focus is not performed, it is determined whether or not automatic exposure by hyperfocal distance is performed (step S47). If automatic exposure by hyperfocal distance is performed, the hyperfocal distance L∞ is determined. Is set to an arbitrary value INPUT (step S48), the focal length f set in step S43, the allowable confusion circle diameter δ set in step S37, step S39 or step S40, and the error set in step S48. Based on the focal length L∞, the expression “F = f ² / (δ · L∞)” is executed to calculate the aperture value F (step S46).

If automatic exposure is not performed by the hyperfocal distance, it is determined whether or not automatic exposure is performed by setting the depth of field (step S49). When automatic exposure is performed by setting the depth of field, A desired front depth of field Tf or rear depth of field Tr is input (step S50), and using the input value, the expression “L∞ = (L ² / Tf−L) or L∞ = (L ² / Tr−L) ”is calculated to set the hyperfocal length L∞ (step S51), and then the focal length f set in step S43 and the allowable circle of confusion set in step S37, step S39, or step S40. Based on the diameter δ and the hyperfocal distance L∞ set in step S51, the expression “F = f ² / (δ · L∞)” is executed to calculate the aperture value F (step S46).

If automatic exposure is not performed by setting the depth of field, it is determined whether or not automatic exposure is performed by setting the depth of field limit (step S52), and automatic exposure is performed by setting the depth of field. In this case, a desired depth limit near point Lmin or depth far point Lmax is input (step S53), and the expression “L∞ = L·Lmin / (L−Lmin) or L∞ = L is used using the input value. After calculating “Lmax (L−Lmax)” and setting the hyperfocal length L∞ (step S54), the focal length f set in step S43 and the tolerance set in step S37, step S39 or step S40 are set. Based on the confusion circle diameter δ and the hyperfocal distance L∞ set in step S54, the expression “F = f ² / (δ · L∞)” is executed to calculate the aperture value F (step S46).

  If automatic exposure is not performed by setting the depth of field limit (if the determination result in step S52 is “NO”), an arbitrary value is input as the aperture value F (step S55), and the above step S46 is performed. Pass.

  Next, an optimum shutter speed (1 / T) is calculated and set based on the exposure amount (EV) and the aperture value F (step S56), and the shutter speed (1 / T) and the aperture value F are calculated. It is determined whether it is within the usage range (step S57). If it is not within the usage range, exception processing is executed (step S58). If it is within the usage range, the through image of the subject is displayed in the viewfinder together with the composition frame of the set aspect ratio, the depth of field setting value, and the like. Displayed (step S59).

  Next, it is determined whether or not the shutter button 8 is depressed (release ON operation) or another key operation (step S60). If another key operation is determined, a process corresponding to the key is executed. If the operation is the menu button 12, the required menu display process is executed (step S61), and then the process returns to step S30. On the other hand, if the release ON operation is determined, the photometry process, the white balance process, and the AF process are performed. After execution (step S62), the electronic imaging unit 31 is driven under the set imaging conditions to capture a full-size square image (a square image having the maximum number of pixels that can be captured by the electronic imaging unit 31) (step S63). When a full-size image is recorded simultaneously (“YES” in step S64), the captured full-size image is encoded and recorded in the image memory (memory card 18) (step S65). Finally, the captured image is recorded. The region of the composition frame set from the above is extracted, and the extracted image is compression-encoded by the compression encoding / decompression decoding unit 46, together with the image size (paper size, aspect ratio, shooting condition data) and image memory ( After storing in the memory card 18) (step S66), the process returns to step S30 again.

  As described above, according to this embodiment, the permissible circle of confusion diameter δ is set according to the selected printing paper size, and the depth-of-field priority automatic exposure is set in accordance with the permissible circle of confusion diameter δ. (AF) shooting and pan-focus shooting can be performed.

Here, the depth of field refers to a range (distance) in which the subject is in focus. That is, when the blur of the image formed near the focal point is equal to or smaller than the allowable circle of confusion circle δ, the blur appears to be in focus. The range before and after the focus on the image side at this time is “depth of field Z”. The near point of the depth of field Z is the front depth of field Tf, and the far point is the rear depth of field Tr. These forward depth of field Tf and rear depth of field Tr are the focal points of the lens. From the distance f, the aperture value F, the shooting distance L, and the allowable circle of confusion diameter δ, it is given by the expression “Tf = δFL ² / (f ² + δFL), Tr = δFL ² / (f ² −δFL)” and The depth of field Z is given by the equation “Z = Tf + Tr = Lmax−Lmin”. However, Lmin is a depth-of-field limit near point, and Lmax is a depth-of-field limit far point.

  The shooting distance at which the depth of field limit far point max is infinite is called “hyperfocal distance L∞ (Hyper Focal Distance)”. With this hyperfocal distance L∞, the distance from ½ of L∞ is It looks in focus up to no distance (∞). For this reason, the depth of field Z can be similarly obtained from the hyperfocal distance L∞ and the shooting distance L as in the following formulas (1) to (4).

L∞ = f ² / δF (1)
Lmin = (L∞ × L) ÷ (L∞ + L) = f ² L / (f ² + δFL) (2)
Lmax = (L∞ × L) ÷ (L∞−L) = f ² L / (f ² −δFL) (3)
Z = Lmax−Lmin = 2δFL ² f ² / (f ⁴ −δ ² F ² L ² ) (4)

  As described above, it is possible to control the focusing accuracy level of AF control according to the size of the printing paper, or to arbitrarily set the distance range in focus, the depth of field, and the like by user operation. In addition, the depth of field is set according to the size of the permissible circle of confusion δ (allowable blur) that is set according to the selected paper size. It is possible to avoid failures such as being in focus or being out of focus. In addition, the allowable accuracy such as AF processing and lens driving can be variably controlled according to the size of the printing paper, so that it is more accurate and more efficient so that the required and sufficient focusing accuracy and depth of field are entered. There is also an advantage that it can be controlled and the average processing time can be increased.

2 is a front view and a rear view of the digital camera 1. FIG. 2 is an internal block diagram of the digital camera 1. FIG. FIG. 6 is a diagram illustrating a display example of the liquid crystal display 15 when a shooting mode is selected, and a diagram illustrating a display example of a printing paper selection screen 53. It is a figure which shows the operation | movement flowchart of the control system. It is a figure which shows the example of a setting calculation of permissible blur (permissible circle of confusion diameter) (delta). It is a figure which shows an example of the data table 56 required for the setting calculation of permissible blur (permissible circle of confusion diameter) (delta). It is a figure which shows an example of the data table 57 required for the setting calculation of permissible blur (permissible circle diameter of confusion) (delta). FIG. 10 is a diagram (1/3) illustrating an operation flowchart when performing AE shooting with priority on depth of field, pan-focus shooting, or the like. FIG. 10 is a diagram (2/3) illustrating an operation flowchart when performing AE shooting with priority to depth of field, pan-focus shooting, or the like. FIG. 3C is a diagram (3/3) illustrating an operation flowchart when performing AE shooting with priority to depth of field, pan-focus shooting, or the like.

Explanation of symbols

1 Digital camera (electronic camera)
20 Imaging system (imaging means)
21 Control system (size specifying means, calculating means, photographing condition changing means)

Claims (4)

Imaging means for photographing a subject under predetermined photographing conditions and generating an image signal of the subject image;
Size designation means for designating the size of the image signal during viewing;
A computing means for computing an allowable circle of confusion suitable for the viewing size;
An electronic camera comprising: a photographing condition changing unit that changes the photographing condition corresponding to the allowable circle of confusion. The electronic camera according to claim 1, wherein the photographing condition is any one or all of an aperture, a focal length, a depth of field, an exposure, a hyperfocal distance, and a focal depth. An imaging step of shooting a subject under predetermined shooting conditions and generating an image signal of the subject image;
A size designating step for designating the size of the image signal during viewing;
A calculation step of calculating a permissible circle of confusion suitable for the viewing size;
And a photographing condition changing step of changing the photographing condition corresponding to the permissible circle of confusion. 4. The electronic camera control method according to claim 3, wherein the photographing condition is any one or all of an aperture, a focal length, a depth of field, an exposure, a hyperfocal distance, and a focal depth.

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