JP2006243371A - Electronic flash apparatus, its control method and digital still camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To emit strobe light by appropriately controlling the quantity of the strobe light. <P>SOLUTION: When a release button is depressed, prior to normal photographing for recording a still image, pre-photographing is performed. During the pre-photographing, the prescribed quantity of strobe light is emitted so as to exposure in an image sensor. The brightness of an object is separately obtained in respective small areas obtained by dividing a photographed image photographed during the pre-photographing into a plurality of areas, and the quantity of strobe light required for normal-photographing is decided based on the highest brightness in the obtained object brightness and the quantity of the strobe light emitted during the pre-photographing. The normal emission of the strobe light is controlled so as to emit the decided quantity of the strobe light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dimming strobe device, a control method therefor, and a digital still camera.

  As a strobe device that controls the amount of strobe light so that an appropriate exposure amount is obtained, an automatic light control strobe device is known. This automatic dimming strobe device receives the strobe reflected light reflected by the subject during strobe light emission by the light receiving sensor, integrates the amount of strobe reflected light, and when the integrated value reaches a certain level The flash has stopped firing.

  In a single-lens reflex camera equipped with an automatic light control strobe device, a light-receiving sensor is placed toward the photographic film so that the stroboscopic light reflected by the photographic film is transmitted through the photographic lens. There is also a so-called TTL (Through The Lens) dimming method.

  The light receiving sensor of such a strobe device receives reflected light from the light receiving area set in the photographing screen. For example, the central portion in the photographing screen is used as the light receiving area. In some cases, the entire photographing screen is used as a light receiving area, and a large weight is given to the light receiving result at the center of the screen.

On the other hand, a digital still camera that captures a subject image with an image sensor (imaging device) such as a CCD image sensor and records the obtained image data on a recording medium such as a memory card is widely used. Patent Document 1 discloses a digital still camera equipped with a TTL light control type strobe device.
JP-A-6-197270

  By the way, in the dimming strobe device as described above, when the light receiving area does not overlap the main subject, for example, when it overlaps the background away from the main subject, the light receiving sensor does not receive the strobe reflected light so much. The amount of light is greater than the appropriate amount. In this way, if the position of the light receiving area and the main subject do not match, the result is that the main subject is excessively exposed to strobe light, resulting in overexposure and so-called whiteout. There was a problem to do. In addition, if the ratio of the subject to the shooting screen is high, such as a flat wall, the amount of light received by the light receiving sensor increases and the amount of strobe light becomes less than the appropriate amount, resulting in underexposure. It was. This is because in general shooting, the main subject and the light receiving area are rarely positioned completely, and the amount of received light that stops the strobe light emission is determined in consideration of a certain amount of deviation.

  The present invention has been made to solve the above problem, and a dimmable strobe device capable of appropriately controlling the amount of strobe light regardless of the size of the subject, the position in the shooting screen, and the like, and the control method thereof An object of the present invention is to provide a digital still camera equipped with the strobe device.

To achieve the above objective,
According to another aspect of the present invention, there is provided a flash device for shooting a subject image at the time of pre-emission, strobe light emitting means for performing pre-emission before main shooting for shooting a subject image, and main emission synchronized with main shooting. Based on the image sensor that outputs and the shooting signal from this image sensor, the luminance of the subject is obtained for each of the small areas obtained by dividing the shooting screen into a plurality of areas, and based on the luminance of the subject and the strobe light amount of the pre-flash, A light amount determining unit that determines a strobe light amount of the main light emission; and a light amount control unit that controls the strobe light emitting unit so that the main light is emitted with the strobe light amount determined by the light amount determining unit.

  3. The strobe device according to claim 2, wherein the light quantity determining means extracts the highest brightness from the brightness of the subject in each small area, and based on the extracted brightness and the pre-flash light quantity, the main flash light quantity. Is to be determined.

  In the strobe device according to claim 3, the light quantity determining means extracts a predetermined number of small areas in descending order of luminance, and based on the extracted average luminance of each small area and the pre-flash strobe light quantity. The amount of light is determined.

  In the strobe device according to claim 4, the light quantity determining means extracts each small area whose luminance difference from the highest brightness is within a predetermined range, and calculates the average brightness of each extracted small area and the pre-flash light quantity. Based on the above, the strobe light amount of the main light emission is determined.

In the strobe device according to claim 1, when the number of small areas in which the luminance difference from the highest luminance in the shooting screen is within a predetermined range is equal to or greater than a predetermined ratio, The correction is made so as to reduce the amount of light.

  In the strobe device according to the sixth aspect, the flash light amount of the main light emission is determined without using the luminance of the small area at the periphery of the photographing screen among the small areas obtained by dividing the photographing screen into a plurality of parts.

  In the strobe device according to claim 7, the light quantity determination means obtains a correction luminance weighted to the luminance of the subject in each small area, extracts a small area having the highest correction luminance from each correction luminance, and extracts the extracted small area. The main flash light quantity is determined based on the brightness of the area and the pre-flash light quantity.

  9. The strobe device according to claim 8, wherein the light quantity determining means obtains a correction luminance weighted to the luminance of the subject in each small region, extracts a predetermined number of small regions in descending order of the correction luminance, and extracts each small region extracted. The main flash light quantity is determined on the basis of the brightness and the pre-flash light quantity.

  In the strobe device according to claim 9, the light amount determination means obtains a correction luminance weighted to the luminance of the subject in each small area, and each luminance difference between the highest correction luminance and the correction luminance is within a predetermined range. A small area is extracted, and the strobe light amount of the main light emission is determined based on the extracted luminance of each small region and the strobe light amount of the pre-light emission.

  The strobe device according to claim 10, wherein the light amount determination means is configured to cause the luminance difference between the highest correction luminance and the correction luminance to be larger than a predetermined number when the number of extracted small regions within a predetermined range is larger. A predetermined number of small areas are extracted in descending order of the corrected luminance, and the main flash light quantity is determined based on the extracted luminance of each small area and the pre-flash light quantity.

  12. The strobe device according to claim 11, wherein the light amount determining means determines the strobe light amount based on the weighted average of the corrected luminance of each small area and the pre-flash light amount when determining the main light strobe light amount. It is what you do.

  In a digital still camera according to a twelfth aspect of the present invention, the digital still camera is provided with the strobe device. In the digital still camera according to the thirteenth aspect, an image sensor for actual photographing is used as an image sensor for photographing a subject image at the time of pre-emission.

  In the control method for a strobe device according to claim 14, prior to the main photographing for photographing a subject image, pre-photographing with the strobe device emitting light with a predetermined strobe light amount is performed by an image sensor, and pre-photographing obtained from the image sensor is performed. Based on the shooting signal, the brightness of the subject is calculated for each of the small areas obtained by dividing the shooting screen into a plurality of areas, and the flash light quantity for the main shooting is determined based on the brightness of the subject and the flash light quantity for pre-shooting. In this case, the flash light is emitted with the strobe light amount determined in synchronization with the main photographing.

  According to the present invention, pre-photographing with a predetermined strobe light amount is performed prior to the main photographing, and based on the luminance of the subject obtained for each small area obtained by dividing the photographing screen and the strobe light amount at the time of pre-photographing. Since the strobe light intensity for the main shooting was determined and the strobe light was emitted during the main shooting, the main shooting was performed with the appropriate strobe light regardless of the position, size, number of subjects, etc. It can be carried out.

  FIG. 1 shows the appearance of a digital still camera equipped with a strobe device embodying the present invention. A photographing lens 3 and a strobe light emitting unit 4 that irradiates strobe light toward a subject are provided on the front surface of the digital still camera 2. A release button 6 is disposed on the upper surface of the digital still camera 2. By pressing the release button 6, a still image for one frame is shot, and image data obtained by this shooting is recorded on a memory card 7 (see FIG. 2) attached to the digital still camera 2. .

  On the back surface of the digital still camera 2, an LCD (liquid crystal display) 8 (see FIG. 2), operation buttons for performing various settings of the digital still camera 2, and the like are arranged. By viewing the menu displayed on the LCD 8 and operating the operation buttons to give instructions, it is possible to switch between the shooting mode and the playback mode, select the strobe mode, and the like. As the strobe mode, for example, an automatic light emission mode that automatically emits light when the subject brightness is below a predetermined level, a forced light emission mode that forcibly emits light, and a light emission inhibition mode that prohibits light emission can be selected.

  In shooting with flash firing (hereinafter referred to as flash shooting), pre-shooting and main shooting are performed. Pre-shooting is used to determine the amount of strobe light (hereinafter referred to as “main flash”) during actual shooting. From the result, the amount of strobe light at the time of the main flash is determined. In the main shooting, a still image is shot by controlling the light emission time of the main flash so that the strobe light amount determined by the pre-shooting is obtained, and the image data of the shot still image is recorded in the memory card 7. In this example, the pre-photographing is performed after the pre-photographing is performed in response to the full press of the release button 6, but the pre-photographing is performed in response to the half-pressing of the release button 6, and then the full press of the release button 6 is performed. The actual photographing may be performed in response to.

  The electrical configuration of the digital still camera 2 is shown in FIG. The operation unit 11 outputs an operation signal corresponding to the operation of the release button 6 or the operation button. The system controller 12 controls each unit of the digital still camera 2 in response to an operation signal from the operation unit 11.

  The taking lens 3 includes a focus adjustment mechanism, a shutter device 13 that also serves as an aperture, and the like, and is controlled by a system controller 12. Behind the photographic lens 3, a CCD image sensor 14 having a large number of light receiving portions (pixels) on the light receiving surface is disposed. The CCD image sensor 14 is driven by a driver 15 and converts a subject image formed on a light receiving surface by a photographing lens 3 into an analog photographing signal and outputs it as is well known. In this example, imaging is performed using a CCD image sensor, but the image sensor is not limited to this, and a CMOS image sensor, for example, may be used.

  The signal processing unit 16 performs various processes such as noise removal, amplification, conversion to image data, white balance, γ correction, and data compression on the captured signal. Under the shooting mode, noise removal, amplification, conversion to image data, white balance, and γ correction are performed, and the processed image data are sequentially sent to the LCD driver 17. Thereby, the subject image being photographed is displayed on the LCD 8 as a through image. The signal processing unit 16 performs noise removal, amplification, and conversion processing to image data on a captured signal obtained by pre-shooting, and then sends the processed signal to a light amount calculation unit 24 described later. In addition, the signal processing unit 16 performs noise removal, amplification, and conversion processing to image data, and then performs white balance and γ correction, and further compresses the data for the captured signal obtained in the actual imaging. Recording is performed on the memory card 7 via the circuit 18. Note that the recording medium is not limited to a memory card, and various types of recording media can be used, and image data may be recorded in the internal memory of the digital still camera 2.

  Under the reproduction mode, image data is read from the memory card 7 by the interface circuit 18, subjected to various processing by the signal processing unit 16, and then sent to the LCD driver 17. Thereby, the image recorded on the memory card 7 is displayed on the LCD 8.

  In addition, the signal processing unit 16 includes a circuit that detects subject brightness and image data contrast based on the image data, and sends the detected subject brightness and contrast information to the system controller 12. The system controller 12 controls the electronic shutter speed of the CCD image sensor 14 and the aperture of the photographing lens 3 based on the subject luminance information, and controls the focus adjustment of the photographing lens 3 based on the contrast information.

  The strobe discharge tube 21 is arranged at the base of the strobe light emitting unit 4 and is connected to the charge / discharge circuit 22. The charging / discharging circuit 22 applies a trigger voltage to the main capacitor, a charging circuit for charging the main capacitor to a high voltage, and the strobe discharge tube 21, and starts the light emission of the strobe discharge tube 21 with the electric charge accumulated in the main capacitor. A strobe light is composed of a trigger circuit, a light emission stop circuit for stopping light emission of the strobe discharge tube 21, a circuit for setting the strobe light amount of the pre-light emission to a predetermined value, and the strobe discharge tube 21 constitutes strobe light emission means.

  The system controller 12 sends a pre-emission signal to the charge / discharge circuit 22 during pre-photographing. The charging / discharging circuit 22 emits the strobe discharge tube 21 in a predetermined time in response to the input of the pre-emission signal, thereby performing pre-emission with a predetermined strobe light amount. This pre-emission may be a strobe light amount (light emission time) that can determine the strobe light amount of the main light emission, and the number of times of light emission may be one time or more. Note that it is preferable to set a strobe light amount and a light emission pattern so that the pre-light emission is not mistaken for completion of photographing. This pre-emission is performed in synchronization with exposure of the CCD image sensor 17 during pre-photographing (hereinafter referred to as pre-exposure).

  The system controller 12 inputs a main light emission start signal to the charge / discharge circuit 22 at the time of main photographing, and inputs a main light emission stop signal when a main light emission time required as described later has elapsed from the input time point. . The charge / discharge circuit 22 starts light emission of the strobe discharge tube 21 in response to the input of the main light emission start signal, and stops light emission in response to the subsequent input of the main light emission stop signal. Thereby, the main light emission is performed in which the strobe light is emitted for the main light emission time. The charge / discharge circuit 22 is configured to be able to control the amount of strobe light by the light emission time. For example, a main capacitor is provided for each of the pre-light emission and the main light emission, and the charging voltage of the main capacitor is controlled to be constant. A sensor that directly receives the strobe light emitted from the strobe discharge tube 21 is provided, and the amount of strobe light emitted from the strobe discharge tube 21 is detected using this sensor. It is also possible to control to stop the light emission.

  A light amount calculation unit 24 as a light amount determination unit obtains a main light emission time from image data obtained by pre-exposure of the CCD image sensor 17. The light amount calculation unit 24 sequentially performs luminance calculation processing, reference calculation processing, and light amount determination processing. In the luminance calculation process, as shown in FIG. 3, the photographing screen 27 of the CCD image sensor 17 is divided into n × m (9 × 9 in this example) small areas 28, and the luminance corresponding to the luminance for each small area 28. Calculate the data. This luminance data is calculated according to the luminance of the subject in the small area 28 illuminated by pre-emission using the image data of each pixel in the small area 28 to be calculated. In the reference calculation process, reference luminance data is obtained as a reference for calculating the amount of strobe light to be emitted in the main light emission. In this example, luminance data indicating the highest luminance among the luminances for each small region 28 is extracted, and the luminance data is used as reference luminance data.

  In the light amount determination processing, the strobe light amount at the main light emission is determined based on the pre-flash strobe light amount and the reference luminance data, and the light emission characteristic of the strobe discharge tube 21 is taken into consideration so as to obtain an appropriate exposure. Convert to flash time. Assuming that the average reflectance of the subject in the small area 28 having the luminance as the reference luminance data is, for example, the standard reflectance, the luminance at the time of pre-exposure of the small area 28 and the strobe light amount at the time of pre-emission are obtained. On the basis of the above, it is possible to obtain a strobe light amount for properly exposing the subject in the small area 28, and such a strobe light amount is set as a strobe light amount at the time of main light emission. Further, when obtaining the amount of strobe light for main light emission, the aperture and photographing sensitivity for pre-exposure and main light emission are considered.

  When shooting, it is very rare to perform framing so that the main subject is located in the peripheral part of the shooting screen. Rather, the strobe light is strongly reflected by something other than the main subject located in the peripheral part. Therefore, there is a high possibility that an incorrect strobe light amount is calculated. For this reason, in this example, the small area 28 in the peripheral portion in the shooting screen 27 that is hatched in FIG. 3 is excluded from the processing of the light amount calculation unit 24 to reduce the calculation processing amount and reduce the amount of calculation processing. The possibility of an appropriate strobe light level is reduced.

  Next, the operation of the above configuration will be described. When shooting a still image, the digital still camera 2 is turned on and a shooting mode is selected. When the photographing mode is entered, the CCD image sensor 14 starts operating.

  A subject image exposed at each pixel of the CCD image sensor 14 is output as a photographing signal. The photographic signal is sent to the signal processing unit 16, where white balance and γ correction are performed after noise removal, amplification, and conversion to image data. Then, the processed image data is sent to the LCD driver 17. Exposure by the CCD image sensor 14 is repeatedly performed, and image data obtained by the exposure is sequentially sent to the LCD driver 17, so that the subject image being photographed is displayed on the LCD 8 as a moving image.

  On the other hand, the signal processing unit 16 detects the contrast of the image being shot and the subject brightness, and sends the results to the system controller 12 as contrast information and subject brightness information. Based on the contrast information, the focus position of the taking lens 3 is adjusted so that the contrast of the subject image being shot is maximized, and the subject currently being shot is brought into focus. Since this focus adjustment is performed as needed, even if the shooting distance to the subject changes, the focus is adjusted following the change. Further, based on the subject luminance information, the electronic shutter speed of the CCD image sensor 14 and the aperture of the photographing lens 3 are adjusted, and the subject being photographed is adjusted to have a substantially appropriate exposure.

  Select the strobe mode when shooting still images. Next, after observing the through image displayed on the LCD 8 and determining framing, the release button 6 is pressed.

  For example, when the forced flash mode is selected as the flash mode, or when the automatic flash mode is selected and the subject brightness is below a predetermined level, flash photography is performed in response to the pressing operation of the release button 6.

  As shown in FIG. 4, the system controller 12 causes the CCD image sensor 14 to perform pre-exposure at a predetermined electronic shutter speed after switching the aperture of the taking lens 3 to a pre-shooting value. Then, a pre-emission signal is sent to the charge / discharge circuit 22 during this pre-exposure. In response to the input of the pre-emission signal, the charge / discharge circuit 22 causes the strobe discharge tube 21 to emit light in a predetermined emission time.

  In this way, pre-emission with a predetermined strobe light amount is performed during pre-exposure, and pre-emission strobe light reflected by the subject is received by the CCD image sensor 14. After completion of the pre-exposure, a photographing signal is output from the CCD image sensor 14. Then, the image pickup signal is subjected to noise removal and amplification with a predetermined gain in the signal processing unit 16, and then converted into image data for each pixel and sent to the light amount calculation unit 24.

  Based on the image data from the signal processing unit 16, luminance calculation processing is performed by the light amount calculation unit 24, and luminance data is calculated for each of the small areas 28 obtained by dividing the photographing screen 27. When the luminance data is calculated for all the small areas 28, the reference calculation process is performed, and the luminance data having the highest luminance is extracted from each luminance data, and this is used as the reference luminance data.

  For example, as shown in FIG. 5, the luminance data of each small area 28 of the photographing screen 27 is set to E01, E02,... E77, and as shown in FIG. In the case of “E72”, the luminance data E43 having the highest luminance is the reference luminance data.

  Note that each time the luminance for one small region 28 is calculated in the luminance calculation process, the maximum luminance may be obtained by comparing the calculated luminance with the highest luminance so far.

  After obtaining the reference luminance data as described above, the light amount calculation unit 24 performs a light amount determination process, taking into account the aperture of the photographing lens 3 at the time of pre-shooting and main shooting, and the reference luminance data and the pre-flash strobe light amount. Based on the above, the strobe light amount at which the small area 27 having the maximum luminance is appropriately exposed is obtained. Then, the amount of strobe light is converted into the main light emission time in consideration of the light emission characteristics of the strobe discharge tube 21 and the like, and is sent to the system controller 12.

  When the system controller 12 receives the main light emission time, the main photographing is started. After the aperture of the photographing lens 3 is set, the main exposure by the CCD image sensor 14 is started. Further, a main light emission start signal is input to the charge / discharge circuit 22 from the system controller 12. When the main light emission start signal is input, the charge / discharge circuit 22 starts strobe light emission, and the strobe light is emitted from the strobe light emitting unit 4 toward the subject.

  When the main light emission time calculated by the light amount calculation unit 24 as described above has elapsed from the input time point of the main light emission start signal, a main light emission stop signal is sent from the system controller 12 to the charge / discharge circuit 22 at that time point. The flash fires. In this way, the main light emission is performed during the main exposure of the CCD image sensor 14, the stroboscopic light of the main light emission is irradiated to the subject, and the reflected light is received by the CCD image sensor 14.

  When the main exposure is completed, the CCD image sensor 14 outputs a photographing signal for the main exposure. The photographing signal is converted into image data after noise removal and amplification by the signal processing unit 16. Then, the image data is subjected to processing such as white balance processing and γ correction, and then the image data for one frame is data-compressed and then recorded on the memory card 7 via the interface circuit 18.

  As described above, the image shot in the main shooting is subjected to the main light emission with the strobe light amount determined by the pre-shooting, so there is no overexposure, no whiteout occurs, and a preferable strobe light amount. It was taken in.

  FIG. 7 shows a second embodiment in which the amount of strobe light at the time of main light emission is determined by the average luminance of a plurality of small areas on the high luminance side. Note that the reference calculation process is the same as in the first embodiment, and the same components are denoted by the same reference numerals and description thereof is omitted.

  In the reference calculation process, the light amount calculation unit 24 rearranges the luminance data obtained in the luminance calculation process in descending order of luminance, extracts a predetermined number of small regions 28 from the highest luminance, and extracts the extracted small regions 28. The average of the luminance data is used as reference luminance data. Then, using the reference luminance data, the strobe light amount of the main light emission is obtained by the light amount determination process. Note that luminance data that satisfies the condition may be extracted without rearranging the luminance data.

  For example, as shown in FIG. 8, the luminance data “E43, E45,... E72” are arranged in descending order of luminance, and the average luminance of the seven small regions 28 on the high luminance side is set as the reference luminance data. In this case, the average of “E43, E45,... E36” becomes the reference luminance data.

  In this way, by using the average brightness of a plurality of small areas on the high brightness side as the reference brightness data, it is possible to make the strobe light amount during the main flash more appropriate regardless of the position of the subject and the number of subjects. .

  FIG. 9 shows a third embodiment in which the light emission amount during the main light emission is calculated based on the average luminance of each small region whose luminance difference from the maximum luminance is within the predetermined luminance difference. It is the same as the first embodiment except that the reference calculation process is different.

  In the reference calculation process, the light amount calculation unit 24 rearranges the luminance data obtained in the luminance calculation process in descending order of luminance, and each small region 28 within a predetermined luminance difference (for example, 3 EV or less) determined in advance with respect to the maximum luminance. And the average of the extracted luminance data of each small region 28 is used as reference luminance data. Then, using this reference luminance data, the strobe light amount of the main light emission is determined by the light amount determination process.

  For example, when the range of the luminance difference is 3EV and the luminance order and the luminance difference are as shown in FIG. 10, each small portion on the high luminance side from E43 having the highest luminance to E22 having the luminance difference within 3EV. The average luminance of the luminance of the region 28 becomes reference luminance data. In this case, the amount of strobe light at the time of the main flash can be made more appropriate regardless of the position of the subject, the number of subjects, and the proportion of subjects in the shooting screen.

  In this example, the luminance data is rearranged. However, the luminance data within a predetermined luminance difference may be extracted after extracting the maximum luminance as shown in FIG. 11 without rearranging the luminance data. Good. In this way, the memory area for extracting the luminance data can be made smaller and the processing time can be shortened compared with the case where rearrangement is performed.

  In the fourth embodiment shown in FIG. 12, the light amount calculation unit 24 calculates the strobe light amount at the time of the main light emission when the luminance difference with respect to the maximum luminance is a predetermined ratio or more with respect to the total number of small regions 28 within a certain range. Correct to reduce.

  For example, when a subject such as a uniform wall is stroboscopically framed to the full shooting screen, there is almost no difference in brightness between the small areas 28, and the strobe using the average brightness as in the embodiment of FIGS. When the light amount is determined, the strobe light amount of the main light emission is determined so that the entire photographing screen is properly exposed, but the photographed image may feel visually bright. However, in this example, under such a shooting condition, the small area 28 having a luminance difference with respect to the maximum luminance within a certain range is more than a predetermined ratio, and correction is made so as to reduce the amount of strobe light during main flashing. Can be reproduced with appropriate brightness.

In the fifth embodiment to the eighth embodiment described below, the reference calculation processing is performed by weighting the luminance of each small region, and each embodiment is the first implementation except that the reference calculation processing is different. The form is the same. In the fifth to eighth embodiments, the shooting screen 27 is divided into 8 × 8 small areas 28 as shown in FIG. 13, for example, and luminance data of each small area 28 is displayed. Is set to “E11, E12,... E88”, and as shown in an example in FIG. 14, the weight is determined so that the small area 28 in the center of the photographing screen 27 becomes a larger value. The difference between attaching the weight “10” to attaching “” corresponds to attaching a difference of about 2.32 (= log ₂ (10/2)) in the EV value. In the fifth to eighth embodiments, the strobe emission time (light quantity) is determined using the small area 28 in the peripheral portion, but the small area 28 in the peripheral portion is used as in the other embodiments described above. It is good also as a structure which does not.

  In the fifth embodiment, as illustrated in FIG. 15, the light amount calculation unit 24 calculates corrected luminance data for each small region 28 by multiplying each luminance data obtained by the luminance calculation processing in the reference calculation processing by a weight. Then, the small area 28 having the largest corrected luminance data is extracted. The light quantity calculation unit 24 sets the extracted luminance data of the small area 28 as reference luminance data. For example, as shown in FIG. 16, when the corrected luminance data is “10 · E44”, “2 · E47”,... “8 · E35” in descending order, the luminance data “E44” is Reference luminance data.

  In the sixth embodiment, as shown in FIG. 17, the light amount calculation unit 24 outputs corrected luminance data obtained by multiplying each luminance data obtained in the luminance calculation processing by a weight in the reference calculation processing, as in the fifth embodiment. Calculation is performed for each of the small areas 28. Then, using the calculated corrected luminance data of each small area 28, the largest corrected luminance data is extracted each small area 28 within a predetermined luminance difference, and the weighted average of the extracted corrected luminance data of each small area 28 Is the reference luminance data.

  For example, as shown in FIG. 18, “10 · E44,“ 2 · E47 ”,...“ 8 · E35 ”in the descending order of the corrected luminance data, up to the corrected luminance data“ 8 · E36 ”. When the difference is within the difference, three weighted averages of the corrected luminance data “10 · E44”, “2 · E47”, and “8 · E36” are obtained and become the reference luminance data. Since the weighted average in this case is given by “(total of extracted corrected luminance data) / (total of weight of extracted corrected luminance data)”, in this example, the reference luminance data is “(10 · E44 + 2 E47 + 8 E36) / (10 + 2 + 8) ".

  In the seventh embodiment, as shown in FIG. 19, in the reference calculation process, the light amount calculation unit 24 rearranges the small areas 28 in the descending order of the corrected luminance data obtained by multiplying the luminance data by the weight. A predetermined number of small regions 28 are extracted from the largest one. Then, the weighted average of the corrected luminance data of each extracted small area 28 is set as reference luminance data.

  In the eighth embodiment, as shown in FIG. 20, each small region 28 within a predetermined luminance difference is extracted in the same manner as in the sixth embodiment using the corrected luminance data. When the number of the extracted small regions 28 is within a predetermined number, a weighted average of the corrected luminance data of the extracted small regions 28 is set as reference luminance data.

  On the other hand, when the number of extracted small regions 28 within the predetermined luminance difference is larger than a predetermined number, a predetermined number is further extracted from each small region 28 within the predetermined luminance difference, and the extracted predetermined number The weighted average of the corrected luminance data of the small area 28 is used as reference luminance data. In this extraction, a predetermined number of small regions 28 are extracted from the one having the largest corrected luminance data. As a result, when the number of small regions 28 extracted as being within the predetermined luminance difference is larger than the predetermined number, the strobe light amount is determined in the same manner as in the seventh embodiment.

  According to the fifth to eighth embodiments described above, in any of the embodiments, the main subject is clearly seen from the center of the shooting screen 27 by weighting the smaller small area 28 in the center of the shooting screen 27 to a larger value. Since the strobe light amount is determined using the luminance data of the small area 28 shifted from the center position only when the position of the strobe light is shifted, the strobe light amount during the main light emission can always be made appropriate. Instead of using the weighted average, the strobe light amount can also be determined using the average brightness of the extracted small area.

  In each of the above embodiments, a digital still camera equipped with a strobe device has been described as an example. However, the present invention is not limited to this, and the present invention can also be used for a strobe device used by being mounted on various cameras. Can do. In this case, if an image sensor for pre-photographing is provided in the strobe device, it can be used for a camera without an image sensor.

It is a perspective view which shows the external appearance of the digital still camera which implemented this invention. It is a block diagram which shows the electric constitution of a digital still camera. It shows a state where the shooting screen is divided. It is a flowchart which shows the process sequence in the case of flash photography. It is explanatory drawing which shows the brightness | luminance of each small area | region. It is explanatory drawing which shows the highest brightness | luminance extracted. It is a flow chart showing an example in which an average luminance of a predetermined number of luminances is calculated to determine a strobe light amount. It is explanatory drawing which shows the calculation state of the average luminance in the example of FIG. It is a flow chart showing an example in which an average luminance of a predetermined luminance difference with respect to a maximum luminance is calculated to determine a strobe light amount. It is explanatory drawing which shows the calculation state of the average luminance in the example of FIG. It is a flowchart which shows the example which performs the brightness | luminance extraction of a predetermined brightness | luminance difference with respect to the highest brightness | luminance, without rearranging data. 6 is a flowchart showing an example of correction to reduce the amount of strobe light during main light emission. It is explanatory drawing which shows an example of the division | segmentation state of the imaging | photography screen in 5th-8th Embodiment, and the brightness | luminance of each small area | region. It is explanatory drawing which shows an example of the weight of each small area | region in 5th-8th embodiment. It is a flowchart which shows the example which determines strobe light quantity from the largest correction brightness | luminance among the correction brightness | luminances which weighted the brightness | luminance. It is explanatory drawing which shows the highest correction | amendment brightness | luminance extracted. It is a flowchart showing an example in which the corrected light intensity data with a predetermined luminance difference is extracted from the maximum corrected brightness using the corrected brightness data weighted to the brightness to determine the strobe light amount. It is explanatory drawing which shows the relationship between the correction | amendment luminance data extracted and reference | standard luminance data. 5 is a flowchart showing an example of determining a strobe light amount by extracting a predetermined number of corrected luminance data from a higher one from corrected luminance data weighted with luminance. 5 is a flowchart showing an example in which corrected luminance data with a predetermined luminance difference is extracted from maximum corrected luminance using corrected luminance data weighted with luminance, and the number of extractions is limited.

Explanation of symbols

2 Digital Still Camera 12 System Controller 14 Image Sensor 21 Strobe Discharge Tube 22 Charge / Discharge Circuit 24 Light Amount Calculation Unit 27 Shooting Screen 28 Small Area

Claims (14)

  A flash unit that emits a pre-flash that is emitted before the main shooting and a main flash that is synchronized with the main shooting, an image sensor that captures the subject image and outputs the shooting signal during the pre-flash, and this image Based on the shooting signal from the sensor, the brightness of the subject is determined for each of the small areas obtained by dividing the shooting screen into a plurality of areas, and the light intensity for determining the flash light intensity of the main flash based on the brightness of the subject and the flash light intensity of the pre-flash A strobe device comprising: a determining unit; and a light amount control unit that controls the strobe light emitting unit so that the main light emission is performed with the strobe light amount determined by the light amount determining unit.   The light amount determination means extracts the highest luminance from the luminance of the subject in each small area, and determines the strobe light amount of the main light emission based on the extracted luminance and the pre-flash strobe light amount. The strobe device according to claim 1.   The light quantity determining means extracts a predetermined number of small areas in descending order of luminance, and determines the main flash light quantity based on the extracted average brightness of each small area and the pre-flash light quantity. The strobe device according to claim 1.   The light quantity determination means extracts each small area whose luminance difference from the highest brightness is within a predetermined range, and based on the extracted average brightness of each small area and the pre-flash light quantity, 2. The strobe device according to claim 1, wherein the amount of light is determined.   The light quantity determining means corrects the strobe light quantity of the main flash to be small when the number of small areas in which the luminance difference from the highest luminance in the shooting screen is within a predetermined range is a predetermined ratio or more. The strobe device according to claim 4.   6. The strobe light amount of the main light emission is determined without using the luminance of the small area at the periphery of the photographing screen among the small regions obtained by dividing the photographing screen into a plurality of portions. Strobe device.   The light quantity determining means obtains a corrected luminance weighted to the luminance of the subject in each small area, extracts a small area having the highest corrected luminance from each corrected luminance, and extracts the luminance of the extracted small area and the pre-flash strobe. The strobe device according to claim 1, wherein the strobe light amount of the main light emission is determined based on the light amount.   The light quantity determining means obtains a corrected luminance weighted to the luminance of the subject in each small area, extracts a predetermined number of small areas in descending order of the corrected luminance, and extracts the luminance of each extracted small area and the pre-flash strobe light quantity. The strobe device according to claim 1, wherein the strobe light amount of the main light emission is determined based on the following.   The light amount determination means obtains a correction luminance weighted to the luminance of the subject in each small region, and extracts and extracts each small region where the luminance difference between the highest correction luminance and the correction luminance is within a predetermined range. 2. The strobe device according to claim 1, wherein the strobe light amount of main light emission is determined based on the luminance of each small area and the strobe light amount of pre-light emission.   The light amount determining means is configured to increase a predetermined number of correction luminances in descending order when the number of extracted small areas within a predetermined range is larger than a predetermined number. 10. The strobe device according to claim 9, wherein a small area is extracted, and a main flash light quantity is determined based on the extracted luminance of each small area and the pre-flash light quantity.   The light amount determination means determines the strobe light amount based on the weighted average of the corrected luminance of each small area and the pre-flash light amount when determining the strobe light amount of the main light emission. The strobe device according to any one of 8 to 10.   A digital still camera comprising the strobe device according to any one of claims 1 to 11.   13. The digital still camera according to claim 12, wherein the image sensor that captures a subject image during pre-emission is an image sensor for actual photographing. Prior to the main shooting to shoot the subject image, the image sensor performs pre-shooting with the strobe device emitting light with a predetermined amount of strobe light, and the shooting screen is divided into multiple based on pre-shooting shooting signals obtained from this image sensor The subject's brightness is obtained for each of the small areas, and the strobe light amount for the main shooting is determined based on the brightness of the subject and the strobe light amount for the pre-shooting, and the strobe determined in synchronization with the main shooting is determined. A control method of a strobe device, characterized in that a strobe is emitted with a light amount.

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