JP4812846B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method, and more particularly, to an imaging apparatus and an imaging method that perform imaging based on an exposure program so that an appropriate image can be obtained according to imaging conditions during flash imaging.

  2. Description of the Related Art Conventionally, in an imaging apparatus such as a digital camera, an appropriate exposure value (EV value) corresponding to the brightness of a subject is determined, and in order to obtain the exposure value, a shutter speed (TV value), an aperture value (AV value) A device having an automatic exposure (AE) function for automatically controlling ISO sensitivity (SV value) and the like is known.

  At this time, there are a plurality of combinations of TV values and AV values for the same EV value, and there are a plurality of combinations of these and ISO sensitivities. In an imaging apparatus such as a digital camera, a program diagram (exposure diagram) indicating these combinations is provided in advance in association with a shooting mode, and a technique for performing exposure control based on this program diagram is known. ing.

  In addition, recent digital cameras generally have a flash device such as a strobe (a strobe is a trademark of Strobe Research), and a desired exposure can be obtained only by a combination of a shutter speed and an aperture value. There is also known a technique of controlling exposure by emitting strobe light when the illumination is low, for example (see Patent Documents 1 and 2).

  At this time, in the digital camera, exposure adjustment is performed with reference to luminance information obtained from the preview image. In addition, it is difficult to obtain image information for preview at low illuminance, which requires strobe light during actual shooting. Therefore, the preliminary light emission device provided in the digital camera can be used for preliminary light emission before the actual shooting. To obtain a preview image and control the exposure during actual shooting.

  In other words, at the time of shooting, preliminary light emission is performed prior to the light emission of the flash device for exposure, the reflected light from the subject due to this preliminary light emission is received, and the presence or absence of strobe light emission is selected according to the amount of light received. In other words, a technique for adjusting the exposure amount (so-called TTL exposure control) is used (see, for example, Patent Documents 3 and 4).

  By the way, when the light control is performed, the received light amount of the entire screen obtained by the preliminary light emission is used singly, and the light is adjusted according to the received light amount, the main subject in the imaging scene (hereinafter also referred to as the main subject). In addition to various subordinate subjects such as the background, in general, the light control amount is obtained in association with the shooting distance and reflectance of all the subjects in the shooting scene. May be overexposed (overexposed) or underexposed (underexposed).

  For example, when dimming, if there is a distance difference between the main subject and the background, the strobe light diffuses and attenuates as the distance increases, so the strobe reflected light from the background is smaller (darker) and compared to the background. As a result, the stroboscopic reflected light of the subject becomes large (brighter), and a phenomenon occurs in which the main subject is overexposed on the entire imaging screen during shooting.

  Further, during dimming, there is a possibility that a dimming error with respect to an appropriate light emission amount may occur due to the reflectance of the subject itself. For example, if there is a highly reflective object with a white wall or glossy surface in the background of the main subject, dimming to reduce the amount of reflected light from the background, the main subject that is the subject of the shooting On the other hand, there is a risk of underexposure.

JP 2006-47417 A JP 2007-256907 A JP-A-6-141230 JP-A-6-67256

  However, according to the conventional exposure program diagram, the setting coordinates of AV, TV, SV, etc. are provided based on the luminance information acquired in the preview image, but the flash emission amount is arbitrarily set according to the shooting scene. There is room for further improvement because it does not have a strobe coordinate program diagram that can be used. Also, since there is no program chart for strobe control corresponding to the distance difference between the main subject and the background, there is room for improvement.

  For example, when the ISO sensitivity is lowered and the strobe light is increased, when the distance between the main subject and the background is large, the amount of strobe light applied to the background may be drastically reduced and the background may appear extremely dark. On the other hand, if the ISO sensitivity is increased by suppressing the strobe light in order to avoid this phenomenon, there arises a problem that the S / N ratio deteriorates.

Therefore, the present invention provides a program diagram for strobe control corresponding to the difference in distance between the main subject and the background, and can provide an imaging method that can set the strobe light amount and exposure conditions appropriately and is excellent in convenience. Objective.

The invention according to claim 1, which has been made to achieve such an object, includes an imaging device in which a plurality of photoelectric conversion elements are arranged in a matrix and outputs image data of a subject imaged according to the amount of incident light, and imaging. In this case, a flash device that emits a predetermined amount of auxiliary light to the subject and a flash program diagram that sets the light emission amount of the flash device and the ISO sensitivity of the image sensor in accordance with the brightness of the shooting screen are used. In an imaging method of an imaging apparatus comprising: a flash program; and an exposure control unit that adjusts an incident light amount when shooting the subject using the flash program, image signals output from each of the photoelectric conversion elements When the pixel signal is used, a plurality of luminances each having a predetermined number of pixel signals as a unit are generated in a matrix form on the photographing screen, and the image capturing apparatus is configured to generate the luminance for each unit. A distance information detection procedure for detecting a distance to, and obtaining an average value of the distance for each unit, obtaining an absolute value of a difference value between the average value and the distance to the subject for each unit; Then, a normalization coefficient is calculated by dividing the sum of absolute values of the difference values by the number of one unit, and the flash device emits light as the normalization coefficient increases based on the calculated normalization coefficient. Using an exposure generation procedure that corrects a ratio between the light emission amount of the flash device and the ISO sensitivity of the image sensor in the flash program diagram so as to increase the ISO sensitivity of the image sensor by decreasing the amount. Features.

According to the imaging method of claim 1 , in the shooting screen, a plurality of luminances each having a predetermined number of pixel signals as one unit are generated in a matrix, and the distance from the imaging device to the subject is determined for each unit. The distance information detection procedure to be detected and the average value of the distance for each unit are obtained, the absolute value of the difference value between the average value and the distance to the subject is obtained for each unit, and then the sum of the absolute values of the difference values Is divided by the number of units to calculate a normalization coefficient, and based on the calculated normalization coefficient, the light emission amount of the flash device is decreased as the normalization coefficient increases, so that the ISO sensitivity of the imaging device is increased. in, because of the use of exposed generation procedure for correcting the ratio of the ISO sensitivity of the light emission amount and the image sensor of the flash device in a flash program diagram, according to the distance difference between the photographic material and the background, proper light emitting amount And exposure conditions can be set for convenience It can be.

Next, the invention described in claim 2 is the imaging method according to claim 1, comprising a shutter and aperture in the imaging apparatus, as the flash program diagram, the luminance information representing the brightness of the photographic field A first program diagram for setting the light emission amount and ISO sensitivity parameters and the exposure value of the exposure control unit in association with each other, and a shutter speed and an aperture value for setting the shutter speed and aperture value in association with the exposure values. A second program diagram, and a third program diagram for setting the ISO sensitivity of the image sensor and the light emission amount of the flash device in association with the parameters of the light emission amount and the ISO sensitivity. To do.

According to the imaging method of the second aspect, as the flash program diagram, the light emission amount and ISO sensitivity parameters of the flash device and the exposure value of the exposure control unit are associated with the luminance information indicating the brightness of the screen. The first program diagram to be set, the second program diagram to set the shutter speed and the aperture value in association with the exposure value, the ISO sensitivity of the image sensor in association with the light emission amount and ISO sensitivity parameters a third program diagram for setting the light emission amount of the flash device, than are used, depending on the shooting screen, shutter speed, aperture value, ISO sensitivity, high quality and can set the light emission amount of the flash device A convenient image can be obtained.

Next, the invention according to claim 3 is the imaging method according to claim 1 or 2 , further comprising a preliminary light emission procedure for performing preliminary light emission before the main photographing, wherein the distance information detection procedure is performed on the photographing screen. Based on a reference distance acquisition procedure for acquiring a reference value of a distance from the imaging device corresponding to the specific area to the subject, and a predetermined pixel signal based on image data of the subject obtained by photographing without the preliminary light emission Based on a first luminance generation procedure for generating a plurality of first luminances each having a number of as a unit over a predetermined image area, and image data of the subject obtained by performing the preliminary light emission A second luminance generation procedure for generating a plurality of second luminances with the number of the predetermined pixel signals as one unit so as to be paired with the first luminance, and for each unit, from the second luminance Subtract the first luminance to A luminance difference calculation procedure for calculating a luminance component of preliminary light emission, and for each unit, the first luminance and the luminance component of preliminary light emission calculated in the luminance difference calculation procedure are respectively set to a predetermined target luminance. A parameter generation procedure for generating a first parameter and a second parameter for determining a first subject distance from the imaging device to the subject, using the ratio to obtain a ratio with the target brightness, First distance information generation for generating the first subject distance for each unit based on the first and second parameters and the exposure value at the time of the preliminary light emission in the second luminance generation procedure. A procedure, a correction value calculation procedure for calculating a difference between the first object distance located in the specific area and a reference value of the object distance and using the difference as a correction value, and the correction for each unit. The correction value generated in the value calculation procedure And a second distance information generating procedure for correcting the first subject distance and generating a second subject distance, wherein the parameter generating procedure uses MVa as the first parameter and the second parameter as the second parameter. MVb, the target brightness Yt, the first brightness Ya, and the preliminary light emission brightness component Yb, the first parameter is MVa = LOG ₂ (Ya / Yt), the second brightness The parameter is calculated by an arithmetic expression of MVb = LOG ₂ (Yb / Yt), the first distance information generation procedure is DX, the apex value of the first subject distance is DX, the first luminance generation procedure, and the second luminance When the apex value of the shutter speed at the time of shooting in the generation procedure is expressed as TV, and the apex value of the guide number of the preliminary flash of the flash device is expressed as GV, the apex value of the first subject distance DX = (MVa−MVb) / 2− (5-TV−GV) / 2, and the correction value calculation procedure sets the correction value to OFFSET and the first subject distance in the specific area When the apex value is expressed as DX _(base) and the apex value of the reference value of the subject distance in the specific area is expressed as DV _(base) , the correction value is calculated as follows: OFFSET = DX _(base) −DV _(base) When the second distance information generation procedure expresses the apex value of the second subject distance as DV, the apex value of the first subject distance as DX, and the correction value as OFFSET, By calculating the apex value of the subject distance of 2 with the formula DV = DX−OFFSET, the second subject distance is estimated and calculated for each unit, and for each unit, The serial second object distance is detected as a distance from the imaging apparatus to the subject, it is characterized.

By the imaging method according to claim 3 lever, first it is more generated in a matrix on the entire shooting screen, in association with the second luminance, respectively, subject distance (second is the object distance) It can be measured.

The imaging method of the present invention generates a plurality of luminances in a matrix form with a predetermined number of pixel signals as one unit on a shooting screen, detects the distance from the imaging device to the subject for each unit, and then Find the average distance for each unit, find the absolute value of the difference between the average value and the distance to the subject for each unit, and then divide the sum of the absolute values of the difference values by the number of units. In the flash program diagram so as to increase the ISO sensitivity of the imaging device by decreasing the light emission amount of the flash device as the normalization coefficient increases, based on the calculated normalization coefficient. By correcting the amount of light emitted from the flash device and the ISO sensitivity of the image sensor, the amount of strobe light and exposure conditions can be set appropriately according to the difference in distance between the subject and the background, and convenience can be improved.

In the imaging method of the present invention , the light emission amount and ISO sensitivity parameters and the exposure value are set according to the first program diagram, and then the shutter speed and aperture value corresponding to the exposure value are set according to the second program diagram. In addition, the ISO sensitivity and the light emission amount of the flash device can be set by the third program diagram. Thereby, the shutter speed, the aperture value, the ISO sensitivity, the light emission amount of the flash device, and the like can be set according to the shooting screen, and the convenience can be improved.

Further, the imaging method of the present invention can measure subject distance information by acquiring image data with or without preliminary light emission and associating with a plurality of luminance coordinates generated in a matrix on the entire photographing screen.

1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention. It is explanatory drawing of subject distance information generation | occurrence | production in the imaging device of the Example. It is a flash program diagram in the imaging device of the embodiment. It is explanatory drawing at the time of correct | amending the light emission amount on a flash program diagram based on the deviation of distance information in the imaging device of the Example. FIG. 2 is an explanatory diagram when creating a flash program diagram in the imaging apparatus of the embodiment, where (a) is a diagram showing preset parameters, and (b) is a range of the first program diagram. Explanatory drawing of setting, (c) is explanatory drawing of the range setting of a 2nd program diagram. FIG. 4 is an explanatory diagram when creating a flash program diagram in the embodiment, where (d) is an explanatory diagram of setting a range of the third program diagram, and (e) is the first to third program diagrams. It is the figure which added control coordinates to. It is explanatory drawing showing the process sequence of the imaging method of a present Example.

As illustrated in FIG. 1, the imaging device 1 captures an object (imaging signal S) and outputs a digital image signal, and the incident light amount and flash using the digital image signal input from the imaging unit 100. An exposure control device 200 that adjusts the light emission amount of the device 13 (corresponding to a so-called exposure control unit in the present invention) and an exposure program storage unit 50 for exposure control are provided. In addition, the exposure control apparatus 200 is provided with a function as distance information detection means for detecting distance information for each area of the shooting screen.

The imaging unit 100 includes a front lens 2 that guides subject light into the imaging unit 100, an iris (aperture) 3, a focus lens 5, a shutter 6, and a filter that removes harmful infrared rays, reflected light, and the like (infrared removal filter and optical). 7 is an image sensor (CCD: Charge Coupled Devices) 8, AFE (Analog Front End) 9 which converts an analog image signal output from the image sensor 8 into a digital image signal, and outputs Iris 3. A detection unit 16 that detects the drive amount of Iris 3 via the Iris drive unit 15 and sensor 16a, a focus drive unit 17 that performs slide drive in the optical axis direction (X direction in FIG. 1) of the focus lens 5, and a sensor 18a. The detecting unit 18 for detecting the slide amount of the focus lens 5, the image sensor 8 and A A TG (Timing Generator) 19 for controlling the FE 9 at a predetermined cycle is provided.

  In addition, the imaging unit 100 includes a flash device (for example, a strobe) that irradiates a subject with a predetermined amount of light, and a reference distance detection that detects a distance from the imaging unit 100 to the subject in association with a specific region of the imaging region. Means 14, etc. are provided. Then, before photographing the subject, the imaging device 1 first performs preliminary light emission toward the subject using the flash device 13, and the exposure control device 200 is used for the distance to the subject and the irradiation light of the flash device 13. The reflectance of the subject is measured, and the exposure amount at the time of actual photographing is set based on these measurement results.

  The imaging element 8 is configured such that a plurality of photoelectric conversion elements are arranged in a matrix, and the imaging signal S is photoelectrically converted for each photoelectric conversion element to output an analog image signal.

  The AFE 9 is a correlated double sampling circuit (CDS: Correlated Double Sampling) 10 that removes noise from an analog image signal output via the image sensor 8, and an image that has been correlated double sampled by the correlated double sampling circuit 10. A variable gain amplifier (AGC) 11 that varies the ISO sensitivity (SV) by amplifying the signal, and an analog image signal from the image sensor 8 input via the variable gain amplifier 11 is converted into a digital image signal. An image signal configured by the A / D converter 12 and the like and output from the image sensor 8 is converted into a digital image signal (hereinafter also referred to as a pixel signal) at a predetermined sampling frequency, and is output to the exposure control device 200. .

The reference distance detection means 14 is a focus when an appropriate degree of focus is obtained in a specific region of the shooting screen (in this embodiment, the position B in FIG. 2A and the center of the screen). The reference distance from the focus lens 5 to the subject (so-called reference value of the distance from the imaging device to the subject in the present invention) DV _(base) is detected in association with the position information of the lens 5. Yes. In the present embodiment, DV _(base) is an APEX value based on a distance of 1 m, and an actual distance L is calculated using an expression of DV _(base) = LOG ₂ (distance L / 1 m). Has been converted.

  The reference distance detection unit 14 is configured to detect the reference distance to the subject using the principle of triangulation or the like based on the reflected light from the subject corresponding to the specific area instead of the position information of the focus lens 5. May be. In the present embodiment, the specific area when detecting the reference distance to the subject will be described as the position of the center of the screen (position B in FIG. 2A). For example, in FIG. Other positions such as the position of A and the position of C may be selected according to the shooting conditions.

  Note that the imaging unit 100 may be configured using a CMOS (Complementary Metal Oxide Semiconductor) sensor instead of the imaging device 8, the correlated double sampling circuit 10, the variable gain amplifier 11, the A / D converter 12, and the like. .

Next, the exposure control device 200 is generated by the luminance signal generation unit 21 and the luminance signal generation unit 21 that generate a luminance signal having a predetermined number of pixels as a unit based on the digital image signal input from the imaging unit 100. A luminance buffer 22 that stores the luminance signal in association with the presence or absence of preliminary light emission, a strobe light luminance calculation means 25 that calculates a luminance signal of only the flash device 13 from the luminance signal with or without preliminary light emission, and generates a subject distance for each luminance coordinate. Luminance coordinate distance information generation means 26, reflectance calculation means 32 for calculating the reflectance of the subject for each luminance coordinate, subject distance information for each luminance coordinate and reflectance calculation means 32 generated by the luminance coordinate distance information generation means 26 Recording means 33 for recording the reflectance and the like for each calculated luminance coordinate, a photographing exposure setting unit 42 for setting exposure conditions for photographing, and a CPU (Central Pro The CPU 40 controls each process of the exposure control device 200 in accordance with a control program stored in the ROM 41. The CPU 40 includes a reading unit (ROM) 40, a ROM (Read Only Memory) 41, and the like.

  The luminance generation means 21 scans the digital image signal output from the AFE 9 and generates a luminance signal with four pixel signals of two pixels in the horizontal direction and two pixels in the vertical direction as a unit. As a result, a plurality of luminance signals are generated in a matrix in the imaging region, and each luminance signal is stored in the luminance buffer 22 in association with the unit of luminance coordinates (for example, the central coordinates of four pixels). Is done. Note that one unit for generating the luminance signal is not limited to two horizontal pixels and two vertical pixels, and may be set so that the luminance signal can be generated in a matrix in the imaging region.

The luminance buffer 22 is associated with presence / absence of preliminary light emission of the flash device 13, and stores a luminance signal (Ya _{(h, v)} ) obtained by photographing without preliminary light emission for each luminance coordinate. And a second luminance buffer 24 for storing a luminance signal (Yc _{(h, v)} ) obtained by photographing with preliminary light emission.

The strobe light luminance calculating means 25 stores the luminance signal (Yc _{(h, v)} ) stored in the second luminance buffer 24 for each luminance coordinate from the first luminance buffer 23 using (Equation 1). The luminance signal (Yb _{(h, v)} ) of only the strobe light at the time of preliminary light emission is calculated by subtracting the luminance signal (Ya _{(h, v)} ).
(Formula 1) Yb _{(h, v)} = Yc _{(h, v)} −Ya _{(h, v)}
Note that the subscripts _{(h, v} ) of Ya, Yb, and Yc in (Expression 1) represent luminance coordinates in the horizontal direction and the vertical direction of the imaging region.

Next, the luminance coordinate distance information generating unit 26 uses, for each luminance coordinate, the luminance signal Ya stored in the first luminance buffer 23 and a predetermined luminance signal Yt that is set in advance using (Equation 2). The strobe light calculated by the strobe light luminance calculation unit 25 using the first parameter calculation unit 27 that calculates the first parameter MVa for obtaining the first subject distance based on the ratio of A second parameter calculation unit for calculating a second parameter MVb for obtaining the first subject distance based on a ratio between the luminance Yb and a predetermined luminance signal Yt;
(Formula 2) MVa _{(h, v)} = LOG ₂ (Ya _{(h, v)} / Yt)
(Formula 3) MVb _{(h, v)} = LOG ₂ (Yb _{(h, v)} / Yt)

Further, the luminance coordinate distance information generating means 26, for each luminance coordinate, as shown in FIG. 2B from the first parameter MVa, the second parameter MVb, the exposure condition at the time of preliminary light emission, etc. first distance information calculating unit 29 calculates a first object distance (DX _{(h, v))} for each luminance coordinate, as shown in FIG. 2 (c), against the first object distance in the specific area B correction value calculating section 30 for calculating a difference OFFSET reference value of the subject distance _{(DV (base)),} as shown in FIG. 2 (d), first using the correction value OFFSET calculated by the correction value calculating section 30 A second distance information calculation unit 31 that corrects one subject distance (DX _{(h, v )} ) and calculates a second subject distance (DV _{(h, v)} ) is provided.

Specifically, the first distance information calculation unit 29 calculates the first subject distance (DX _{(h, v)} ) for each luminance coordinate using (Equation 4).
(Formula 4) (DX _{(h, v)} ) = (MVa _{(h, v)} -MVb _{(h, v)} ) / 2- (5-TV-GV) / 2

  In (Expression 4), (5-TV-GV) in the term on the right-hand side is a parameter group representing the exposure conditions for preliminary light emission, where TV is the APEX value of the shutter speed, and GV is the preliminary light emission guide of the flash unit 13. The APEX value of the number, the numerical value 5, is a numerical value for correcting the guide number GV based on ISO100.

The correction value calculation unit 30 calculates the correction value (OFFSET) using (Equation 5), and the second distance information calculation unit 31 uses (Equation 6) to calculate the second subject for each luminance coordinate. The distance (DV _{(h, v)} ) is calculated.
(Formula 5) OFFSET = DX _(base) −DV _(base)
(Formula 6) (DV _{(h, v)} ) = DX _{(h, v)} )-OFFSET

Next, the exposure control device 200 is based on the second parameter (MVb), the second subject distance (DV _{(h, v)} ) calculated by the luminance coordinate distance information generating unit 26, the exposure condition for preliminary light emission, and the like. Thus, the reflectance calculating means 32 for calculating the reflectance of the subject for each luminance coordinate, the second object distance (DV _{(h, v)} ) calculated by the luminance coordinate distance information generating means 26 and the reflectance calculating means 32 Recording means 33 or the like for recording the reflected reflectance (RV _{(h, v)} ) or the like is provided. It should be noted that the function of the distance from the imaging device to the subject for each unit in the present invention is expressed by the second subject distance DV _{(h, v)} or the like.

Specifically, the reflectance calculation means 32 uses (Equation 7) to calculate the reflectance (RV _{(h, v)} ) of the subject for each luminance coordinate as shown in FIG.
(Formula 7) (RV _{(h, v)} ) = MVb _{(h, v)} + 2 * DV _{(h, v)} − (GV−AV−5 + SV)
In (Expression 7), (GV−AV−5 + SV) in the term on the right side is a parameter group representing the exposure condition of preliminary light emission, where GV is the APEX value of the guide number of preliminary light emission of the flash device 13, and AV is Iris. The APEX value of the F number of (aperture) 3, the numerical value 5 is a correction value in which the guide number GV is associated with ISO 100, and SV is the APEX value of ISO sensitivity.

Next, in the imaging apparatus 1, the CPU 40 cooperates with the ROM 41, the second subject distance DV _{(h, v)} measured by the subject distance information generating unit 26, and the reflectance information calculated by the reflectance calculating unit 32. According to (RV _{(h, v)} ), an exposure control device function for controlling an exposure amount when photographing a subject is provided.

  Specifically, the CPU 40 uses the measurement result of the subject information to compare the reflectance of the main subject portion in the imaging region with the reference reflectance that is a reference for exposure control, and corrects the reflectance so as to cancel the difference between the two. The exposure amount is controlled by obtaining a value, or the exposure amount is controlled by weighting the main subject portion.

Further, the exposure control apparatus 200 includes the second subject distance DV _{(h, v)} measured by the luminance coordinate distance information generating unit 26 and the reflectance information RV _{(h, v)} calculated by the reflectance calculating unit 32. Is displayed in correspondence with luminance coordinates (which is also the coordinate position of the photographed image).

Then, the exposure control device 200 refers to the second subject distance DV _{(h, v)} and the reflectance RV _{(h, v)} when the user takes a picture _, and selects the main subject portion via an interface (not shown _). It is configured to be selectable.

Next, the photographing exposure setting unit 42 uses the second subject distance DV _{(h, v)} for each unit generated by the luminance coordinate distance information generating unit 26 and the exposure program storage unit 42, and uses the flash program 13. The ISO sensitivity (SV), etc., such as the light emission amount (GV), shutter speed (TV), aperture value (AV), etc. are set.

  The photographic exposure setting unit 42 includes a first exposure generation unit 42a and a second exposure generation unit 42b.

The first exposure generation unit 42a uses the program diagrams 50a to 50c provided in the exposure program storage unit 50 to perform shutter speed (TV), aperture value (AV), ISO sensitivity (SV), In addition, an expected light emission value (LV) of the corresponding flash device is set on the program diagram. Furthermore, the first exposure generating unit 42a corrects the percentage of ISO sensitivity in diagram program line and (SV) emission expected value of the flash device and (LV).

  The exposure program storage unit 50 stores a first program diagram 50a, a second program diagram 50b, a third program diagram 50c, and the like.

  As shown in FIG. 3A, the first program diagram 50a is associated with the luminance (BV) representing the brightness of the shooting screen, and the expected light emission value of the flash device 13 and the ISO sensitivity of the image sensor 3. A parameter (CV) and an exposure value (EV) are set. In the first program, for example, when BV is −7, EV7 and CV14 are set.

  In the second program diagram 50b, as shown in FIG. 3B, the speed (TV) of the shutter 6 and the iris value (AV) of Iris 3 are set in association with the exposure value (EV). . In the second program diagram, for example, TV5 and AV2 are set during EV7.

Third program diagram 50c is, as shown in FIG. 3 (c), in association with parameters of emission expectation and ISO sensitivity of the imaging element 3 of the flash apparatus 13 (CV), ISO sensitivity of the imaging device 1 ( SV) and the expected light emission value (LV) of the flash device are set. In the third program diagram 50c, for example, SV5 and LV9 are set during CV14. The third program diagram 50c is configured such that strobe priority (LV priority) and ISO sensitivity priority (SV priority) can be selected within a range of CV of 5 to 10.

Further, as shown in FIG. 4, the ratio between the ISO sensitivity (SV) and the expected light emission value (LV) of the flash device is corrected in association with the normalization coefficient Pd .

Specifically, the average value (DVave ) of the distance for each luminance coordinate (so-called so-called unit ) is obtained, and then the average value (DVave) and the distance per unit are calculated using (Equation 8). Then, the absolute value of the difference value is calculated , and then the total value of the absolute values is divided by a unit number N (that is, the number of luminance coordinates when the average value is calculated ) to calculate the normalization coefficient Pd. Then, based on the normalization coefficient Pd, the ratio between the ISO sensitivity (SV) and the expected light emission value (LV) of the flash device in the third program diagram is corrected.
(Formula 8) Pd = ((SUM | DV _{(h, v)} −DVave |) / N) / Md
In (Expression 8), Md is a maximum deviation coefficient for normalization, and is set so that the normalization coefficient Pd becomes 1 at maximum. In addition, SUM in (Equation 8) is an operation symbol for obtaining a set sum.

Then, as shown in FIG. 4, for example, when the coordinate before correction is P ₀ and the calculated normalization coefficient is Pd, the coordinate is shifted by Pd along the CV line, and P1 The coordinates are the corrected coordinates. At this time, the values from P _{0 to} P ₂ are set to 1 (the maximum deviation coefficient). As a result, the larger the distance deviation in the shooting screen is, the more the light is corrected by the flash device 13 and the ISO sensitivity is increased. The function of the flash program diagram in the present invention is expressed by the first program diagram 50a, the second program diagram 50b, the third program diagram 50c, and the like .

Next, the second exposure generator 42b corrects the light emission amount according to the reflectance (RVB) calculated by the reflectance calculator using (Equation 9), and corrects it by the first exposure generator 42a. The light emission amount GVs of the flash device 13 is calculated in association with the coordinates of the P1. That is, since the LVs set by the first exposure generation unit 42a is a numerical value in the same spatial coordinates as the SV, it is converted into a light emission value GVs associated with the guide number of the flash device 13.
(Formula 9)
GVs = LOG ₂ ((2 ^ (RVB + GVp + AVs-AVp + SVp-SVs) -2 ^ (MV0 + GVp + TVp-TVs)) / (2 ^ MV1-2 ^ MV1-2 ^ MV0))

In (Equation 9), RVB is a reflectance correction value based on the reflectance of the subject calculated by the reflectance calculation means 32, and GVp is the APEX value of the guide number of the flash device 13 during preliminary light emission. The subscript p assigned to GV, AV, and SV corresponds to the preliminary light emission, and the subscript s corresponds to the main photographing. Further, MV0 is a luminance evaluation value when there is no preliminary light emission, and MV1 is a luminance evaluation value when there is preliminary light emission, and is calculated by LOG ₂ (evaluation luminance value / target luminance value).

  Next, a procedure for creating the first program diagram 50a, the second program diagram 50b, and the third program diagram 50c will be described with reference to FIGS.

  First, as shown in FIG. 5A, a range of exposure control is determined in advance. The AV range is a to b, the TV range is c to d, and the EV range is (a + c) to (b + d). The SV range is e to f, the LV range is g to h, the CV range is (e + g) to I, and the BV range is ((a + c) -I) to ((b + d)-(e + g)). is there.

  Next, in association with the conditions defined in FIG. 5A, EV lines and CV lines are drawn in the range of BV on the BV diagram as shown in FIG. 5B, and FIG. As shown, a TV line and an AV line are drawn on the EV diagram in the range of EV, and an SV line and an LV line are drawn on the CV diagram in the range of CV.

  Next, as shown in FIG. 6D, detailed coordinates of AV and TV are input to the EV diagram, and detailed coordinates of SV and LV are input to the CV diagram. Further, as shown in FIG. 6E, detailed coordinates of EV and CV are input to the BV diagram.

Next, the procedure of the imaging method of the present embodiment will be described with reference to FIG. This procedure is executed by the CPU 40 giving a command signal to each functional unit based on a program stored in the ROM 41. Further, S in FIG. 7 represents a step.

  First, this procedure starts when an activation signal is input to the exposure control apparatus 200 by the user.

  Next, as shown in FIG. 7, in S100, previously calculated information is initialized, and thereafter, the process proceeds to S110.

  Next, in S110, exposure conditions for preliminary light emission of the flash device 13 are set according to the shooting conditions, and then the process proceeds to S120.

Next, in S120, the distance (DV _(base) ) of the specific area at the time of shooting is acquired using the reference distance detection unit 14, and then the process proceeds to S130.

  Next, in S130, the subject is photographed without preliminary light emission from the flash device 14, and then the process proceeds to S140.

Next, in S140, the luminance signal generation means 21 is used to generate a first luminance signal (Ya _{(h, v)} ) having four pixels of two adjacent horizontal pixels and two vertical pixels as one unit. The information is stored in the first luminance buffer 23 in association with the luminance coordinate located at the center of the pixel, and then the process proceeds to S150.

  Next, in S150, the flash device 13 emits light toward the subject (preliminary light emission) according to the exposure condition set in S110, and the subject is photographed. Thereafter, the flow proceeds to S160.

Next, in S160, the luminance signal generating means 21 is used to generate a second luminance signal (Yc _{(h, v)} ) having four pixels of two adjacent horizontal pixels and two vertical pixels as one unit. The brightness coordinates are stored in the second brightness buffer 24 in association with the brightness coordinates located at the center of the pixel, and then the process proceeds to S170.

Next, in S170, the first luminance signal (Ya _{(h, v)} ) generated in S140 from the second luminance signal (Yc _{(h, v)} ) generated in S160 is used for each luminance coordinate using the strobe light luminance calculation means 25 _{. v)} ) is subtracted to calculate the luminance component (Yb _{(h, v)} ) of only the strobe light at the time of preliminary light emission, and then the process proceeds to S180.

Next, in S180, the first parameter calculation unit 27 is used to convert the first luminance signal Ya into the first parameter (MVa) used for obtaining the first subject distance , and the second parameter calculation unit 28 is used. Thus, the luminance component Yb of only the strobe light is converted into the second parameter (MVb) for obtaining the first subject distance , and then the process proceeds to S190.

Next, in S190, the first distance information calculation unit 29 is used to determine the first subject distance (DX _{(h, H,) for} each luminance coordinate based on the first and second parameters and the exposure value of the preliminary light emission set in S110 _{. v))} ) is calculated, and then the process proceeds to S200.

Next, in S200, the correction value calculation unit 30 is used to calculate the difference (OFFSET) between the reference value of the distance and the first subject distance in the specific region in S120, and the correction value for the first subject distance is obtained. After that, the process proceeds to S210.

Next, in S210, the second distance information calculation unit 31 is used to subtract the correction value (OFFSET) calculated in S200 from the first subject distance calculated in S190 to obtain a second subject distance (for each luminance coordinate ( DV _{(h, v)} ) is calculated, and then the process proceeds to S220.

Next, in S220, using the reflectance calculation means 32, the exposure value of preliminary light emission set in S110, the second parameter calculated in S180, and the second subject distance (DV _{(h, v)} ) calculated in S210. Based on the above, the reflectance information (RV _{(h, v)} ) is calculated for each luminance coordinate, and then the process proceeds to S230.

Next, in S230, the recording means 33 is used to record the second subject distance (DV _{(h, v)} ), reflectance information (RV _{(h, v)} ), etc., and then the process proceeds to S240.

  Next, in S240, the first exposure generator 42a is used to calculate the distance deviation normalization coefficient Pd in the shooting screen, and then the process proceeds to S250.

  Next, in S250, the reflectance correction value RVB is generated using the reflectance calculated by the reflectance calculating means 32, and then the process proceeds to S260.

  Thereafter, in S260, the BV coordinates of the current brightness information are calculated based on the exposure information on the preview screen before the main photographing, and then the process proceeds to S270.

After that, in S270, the shutter speed (TV), aperture value (AV), ISO sensitivity (SV) at the time of actual photographing are used using the program diagrams provided in the first exposure generator 42a and the exposure program storage 50. And an expected light emission value (LV) of the corresponding flash device on the program diagram, and the absolute value of the difference between the average value (DVave) of the distance for each luminance coordinate and the distance for each luminance coordinate A value is obtained and the sum of the absolute values is divided by the number of luminance coordinates to obtain a normalization coefficient Pd . Based on the normalization coefficient Pd , the ISO sensitivity (SV) on the program diagram and the light emission expectation of the flash device The ratio with the value (LV) is corrected, and then the process proceeds to S280.

  Next, in S280, the second exposure generation unit 42b is used to correct the light emission amount in accordance with the reflectance correction value (RVB) and to correspond to the expected light emission value LV corrected by the first exposure generation unit 42a. Then, the light emission amount GVs of the flash device 13 is calculated, and GVs, TVs, AVs, and SVs are set as shooting conditions for the main shooting.

  Next, in S290, according to the command signal from the operator, shooting is performed in accordance with the shooting conditions set in S280, and this procedure ends.

As described above, the imaging method described in the present embodiment generates a plurality of luminances in the form of a matrix with the number of predetermined pixel signals as one unit on the shooting screen, and the subject from the imaging device 1 for each unit. Distance DV _{(h, V)} is detected, and then the expected light emission value (LV) of the flash device 13 is calculated using a program diagram for setting the light emission amount of the flash device 13 according to the brightness of the shooting screen. Then, the average value of the distance for each unit (for each luminance coordinate) is obtained, the absolute value of the difference value of the distance with respect to the average value (DVave) is obtained for each unit, and then the absolute value of the difference value The normalization coefficient Pd is calculated by dividing the total by the number of units (N). Based on the calculated normalization coefficient Pd, the light emission amount of the flash device 13 is decreased as the normalization coefficient Pd increases. To increase the ISO sensitivity of the image sensor 8, By correcting the ratio of the expected light emission value (LV) and ISO sensitivity (Sv) in the program diagram, the light emission amount and exposure conditions of the flash device 13 can be appropriately set according to the distance difference between the subject and the background. Convenience can be improved.

In the imaging method described in the present embodiment , the light emission amount and ISO sensitivity parameters (CV) and the exposure value (EV) are set by the first program diagram 50a, and then the exposure value by the second program diagram 50b. The shutter speed (TV) and aperture value (AV) corresponding to (EV) can be set, and the ISO sensitivity (SV) and the expected light emission value (LV) of the flash device can be set by the third program diagram 50c. Thereby, the shutter speed TV, aperture value AV, ISO sensitivity SV, light emission amount GV of the flash device 13 and the like at the time of shooting can be set according to the shooting screen, and convenience can be improved.

In addition, the imaging method described in the present embodiment acquires image data indicating whether or not preliminary light emission is performed, and associates the plurality of brightness coordinates generated in a matrix with the entire photographing screen, so that the second subject distance DV _{(h , V)} can be measured.

Further, the imaging method described in the present embodiment detects a relative position difference between image regions defined based on the second subject distance DV _{(h, v)} for each luminance coordinate, Can be dimmed in accordance with information relating to the relative positional relationship between the subject portions divided by the subject distance DV _{(h, v)} , and the convenience can be further improved.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, Various aspects can be taken.

  The imaging device 1 and the imaging method according to the present invention can be used for photographing with a flash device as auxiliary light when photographing in a dark place.

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Front lens, 3 ... Iris (aperture), 5 ... Focus lens, 6 ... Shutter, 7 ... Filter, 8 ... Imaging device (CCD: Charge Coupled Devices) 9 ... AFE (Analog Front End) DESCRIPTION OF SYMBOLS 10 ... Correlated Double Sampling Circuit (CDS: Correlated Double Sampling), 11 ... Variable Gain Amplifier (AGC), 12 ... A / D converter, 13 ... Flash device (for example, strobe), 14 Reference distance detecting means, 15 ... Iris driving section, 16 ... detecting section, 16a ... sensor, 17 ... focus driving section, 18 ... detecting section, 18a ... sensor, 19 ... TG (Timing Generator), 21 ... luminance signal generating means 22 brightness buff , 23... First luminance buffer, 24... Second luminance buffer, 25... Strobe light luminance calculation means, 26... Luminance coordinate distance information generation means, 27... First parameter calculation section, 28. 1st distance information calculation part, 30 ... correction value calculation part, 31 ... 2nd distance information calculation part, 32 ... reflectance calculation means, 33 ... recording means, 40 ... CPU (Central Processing Unit), 41 ... ROM (Read Only) Memory), 42... Exposure exposure setting unit, 42 a... First exposure generation unit, 42 b... Second exposure generation unit, 50... Exposure program storage unit, 50 a... First program diagram, 50 b. ... 3rd program diagram, 100 ... Image pick-up part, 200 ... Exposure control apparatus.

Claims (3)

An image sensor that has a plurality of photoelectric conversion elements arranged in a matrix and outputs image data of a subject imaged according to the amount of incident light;
A flash device that emits a predetermined amount of auxiliary light to the subject at the time of shooting;
A flash program using a flash program diagram for setting the light emission amount of the flash device and the ISO sensitivity of the image sensor in accordance with the brightness of the shooting screen;
An exposure controller that adjusts the amount of incident light when the subject is photographed using the flash program;
In an imaging method of an imaging apparatus comprising:
When the image signal output from each of the photoelectric conversion elements is used as a pixel signal, a plurality of luminances having a predetermined number of pixel signals as one unit are generated in a matrix on the photographing screen, and A distance information detection procedure for detecting a distance from the imaging device to the subject;
An average value of the distances for each unit is obtained, an absolute value of a difference value between the average value and the distance to the subject is obtained for each unit, and then the sum of the absolute values of the difference values is calculated as the one value. A normalization coefficient is calculated by dividing by the number of units, and based on the calculated normalization coefficient, the light emission amount of the flash device is decreased as the normalization coefficient increases, and the ISO sensitivity of the image sensor is increased. An exposure generation procedure for correcting a ratio between the light emission amount of the flash device and the ISO sensitivity of the image sensor in the flash program diagram,
An imaging method characterized by using. The imaging device includes a shutter and an aperture,
As the flash program diagram,
A first program diagram for setting the light emission amount and the ISO sensitivity parameter and the exposure value of the exposure control unit in association with luminance information representing the brightness of the shooting screen;
A second program diagram for setting a shutter speed and an aperture value in association with the exposure value;
A third program diagram for setting the ISO sensitivity of the image sensor and the light emission amount of the flash device in association with the parameters of the light emission amount and the ISO sensitivity;
Use
The imaging method according to claim 1, wherein: Pre-flash procedure for pre-flash before actual shooting
The distance information detection procedure includes:
A reference distance acquisition procedure for acquiring a reference value of the distance from the imaging device corresponding to the specific area of the shooting screen to the subject;
First, a plurality of first luminances having a predetermined number of pixel signals as a unit are generated in a matrix over a predetermined image area based on image data of the subject obtained by photographing without the preliminary light emission. Luminance generation procedure;
Based on the image data of the subject obtained by shooting with the preliminary light emission, a plurality of second luminances with the number of the predetermined pixel signals as one unit are generated so as to be paired with the first luminance. A second luminance generation procedure to:
A luminance difference calculating procedure for subtracting the first luminance from the second luminance for each unit to calculate a luminance component of the preliminary light emission;
For each unit, the first luminance and the luminance component of the preliminary light emission calculated in the luminance difference calculation procedure are respectively compared with a predetermined target luminance to obtain a ratio with the target luminance, and this ratio A parameter generation procedure for generating first and second parameters when determining a first subject distance from the imaging device to the subject,
First distance information generation for generating the first subject distance for each unit based on the first and second parameters and the exposure value at the time of the preliminary light emission in the second luminance generation procedure. Procedure and
A correction value calculation procedure for calculating a difference between the first object distance located in the specific area and a reference value of the object distance and using the difference as a correction value;
A second distance information generation procedure for correcting the first subject distance using the correction value generated in the correction value calculation procedure for each unit, and generating a second subject distance;
Use
When the parameter generation procedure represents the first parameter as MVa, the second parameter as MVb, the target luminance as Yt, the first luminance as Ya, and the preliminary emission luminance component as Yb, The first parameter is calculated with an arithmetic expression of MVa = LOG ₂ (Ya / Yt), and the second parameter is calculated with MVb = LOG ₂ (Yb / Yt).
In the first distance information generation procedure, the apex value of the first object distance is DX, the apex value of the shutter speed at the time of shooting in the first luminance generation procedure and the second luminance generation procedure is TV, and the flash device When the apex value of the guide number of the preliminary light emission is expressed as GV, the apex value of the first subject distance is calculated by the following equation: DX = (MVa−MVb) / 2− (5-TV−GV) / 2. Calculate
In the correction value calculation procedure, the correction value is OFFSET, the apex value of the first object distance in the specific area is DX _(base) , and the apex value of the reference value of the object distance in the specific area is DV _(base). The correction value is calculated by the following equation: OFFSET = DX _(base) −DV _(base)
When the second distance information generation procedure expresses the apex value of the second subject distance as DV, the apex value of the first subject distance as DX, and the correction value as OFFSET, the second subject distance The second subject distance is estimated and calculated for each unit by calculating the apex value of DV by the formula DV = DX−OFFSET,
Detecting the second subject distance as the distance from the imaging device to the subject for each unit;
The imaging method according to claim 1, wherein the imaging method is characterized.

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