JP5217613B2 - Camera system, camera body and flash device - Google Patents

Description

  The present invention relates to a camera system, a camera body, and a flash device.

  If the color temperature of the external light and the color temperature of the flash light are significantly different during flash photography with the flash device, light with two different color temperatures is irradiated and an uncomfortable image is formed. There is known a camera in which the color temperature is adjusted to the color temperature of outside light (see, for example, Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2003-015179 A

However, if preliminary light emission is performed according to the color temperature of external light during preliminary light emission prior to the main light emission during shooting, the light emission efficiency of the flash differs depending on the color temperature. Accordingly, there is a problem in that it is impossible to sufficiently illuminate a distant subject, and the calculation accuracy of the main light emission amount based on the reflected light amount from the subject at the time of preliminary light emission is lowered.
Further, if the preliminary light emission amount is increased by the amount that the preliminary light emission amount is reduced, there is a problem that the power for the main light emission is insufficient or the power consumption of the battery is increased.

In the camera system according to the first aspect of the present invention, the color temperature of the light emitter is variable, and the flash unit that performs preliminary light emission and main light emission when photographing is performed, and the color temperature of the main light emission is determined based on predetermined information. And a light emission control means for controlling the color temperature of the preliminary light emission to a color temperature equal to or higher than the light emission efficiency of the main light emission , wherein the light emission control means includes the light emission efficiency of the color temperature of the preliminary light emission and the main light emission. The light emission amount of the main light emission is controlled in consideration of the difference between the color temperature and the light emission efficiency.

  According to the present invention, since preliminary light emission is performed at a color temperature that is more efficient than main light emission, it is possible to monitor a distant subject while suppressing power consumption, and an appropriate main light emission amount can be obtained.

  An embodiment in which the present invention is applied to a single-lens reflex digital camera will be described. The present invention is not limited to the camera of the embodiment, but can be applied to other types of cameras, for example, a compact camera with a built-in flash unit (flash device) or a silver salt film camera.

  FIG. 1 is a cross-sectional view showing a configuration of a camera according to an embodiment. In a camera according to an embodiment, a lens unit 2 and a flash unit (flash device) 17 are detachably attached to a camera body 1. The lens unit 2 includes a photographic lens 3 and a motor 4 for adjusting the focus, and the flash unit 17 includes an illumination control circuit 18 and a light emitter 19.

  The camera body 1 includes a main mirror 5, a sub mirror 6, a focus detection unit 7, a focal plane shutter 8, a first image sensor 9, a control device 10, a diffusing screen 11, a condenser lens 12, a pentaprism 13, an eyepiece 14, and reconnection. An image lens 15, a second imaging sensor 16, and the like are provided.

  The first image sensor 9 photoelectrically converts the subject image to generate and output a high-quality image signal. The second image sensor 16 photoelectrically converts the subject image to generate and output an image signal. The image signal output from the second imaging sensor 16 analyzes the shooting scene and calculates the shooting conditions and image processing conditions of the first imaging sensor 9, the light emission conditions (light emission amount, color temperature) of the flash unit 17, and the like. Is used to calculate

  The main mirror 5, the sub mirror 6, the focal plane shutter 8 and the first image sensor 9 are arranged along the optical axis of the photographing lens 3. The finder optical system is disposed in the upper region of the main mirror 5, and the focus detection unit 7 is disposed in the lower region of the sub mirror 6.

  During non-photographing, the main mirror 5 intersects the photographing optical path from the photographing lens 3 to the first image sensor 9, and reflects the light beam from the subject that has passed through the photographing lens 3 upward to guide it to the finder optical system. Yes. On the other hand, at the time of shooting, the main mirror 5 and the sub mirror 6 are flipped upward, and the subject luminous flux that has passed through the shooting lens 3 passes through the focal plane shutter 8 and is guided to the first imaging sensor 9. A subject image is formed on the light receiving surface. The first image sensor 9 photoelectrically converts the subject image to generate an image signal.

  The central portion of the main mirror 5 is a half mirror that transmits light, and a part of the subject light beam that has passed through the main mirror 5 when not photographing is reflected downward by the sub mirror 6 and guided to the focus detection unit 7. The focus detection unit 7 detects the focus adjustment state (defocus amount) of the photographic lens 3 based on the received subject luminous flux.

  The viewfinder optical system includes a diffusion screen 11, a condenser lens 12, a pentaprism 13, an eyepiece lens 14, and a re-imaging lens 15. The diffusing screen 11 is disposed above the main mirror 5, and a subject image is formed by a light beam reflected by the main mirror 5 when not photographing. The subject image formed on the diffusing screen 11 is guided to the photographer's eyes through the condenser lens 12, the pentaprism 13, and the eyepiece lens 14, and is visually recognized by the photographer.

  The subject image formed on the diffusing screen 11 is guided to the second imaging sensor 16 via the condenser lens 12, the pentaprism 13, and the re-imaging lens 15, and the subject image is formed on the second imaging sensor 16. Re-imaged. The second image sensor 16 photoelectrically converts the subject image to generate an image signal. The re-imaging lens 15 and the second image sensor 16 constitute a photometric device for the camera, and the photometric device detects the subject brightness and the color temperature of the subject. Note that the method for detecting the color temperature of the subject is not limited to the method of the embodiment, and the color temperature of the object scene may be recognized by another method using a detector other than the photometric device.

  The control device 10 is composed of peripheral components such as a microcomputer and a memory, and performs various arithmetic operations of the camera.

  The light emitter 19 of the flash unit 17 includes a red LED 19a, a green LED 19b, and a blue LED 19c. The illumination control circuit 18 energizes the three color LEDs 19a to 19c in accordance with the light emission control signal from the control device 10 to emit light. The light emission amounts of the three-color LEDs 19a to 19c are amounts corresponding to the energization currents, and the color temperature of the flash can be changed by adjusting the current ratio of energization to the three-color LEDs 19a to 19c.

  FIG. 2 is a flowchart showing the photographing operation of the camera according to the embodiment. The operation of the embodiment will be described with reference to this flowchart. When the camera is turned on and the release button is pressed halfway, the control device 10 starts the photographing operation shown in FIG.

  In step 101, the second image sensor 16 is driven to acquire an image signal of the subject. In the following step 102, the brightness of the object scene is detected based on the image signal received from the second image sensor 16, and the exposure amount of the first image sensor 9 at the time of shooting is calculated. The color temperature of the background of the main subject and the surrounding environment of the main subject is detected. Let this color temperature be K1.

  In step 103, it is determined whether or not a release button (not shown) has been operated, and the processing in steps 101 to 102 is continued until a release operation is performed. If there is a release operation, the routine proceeds to step 104, where it is determined whether or not the flash unit 17 needs to emit light during photographing. For example, it is assumed that light emission is necessary when the subject brightness detected in step 102 is lower than a predetermined value.

  If the subject brightness is equal to or higher than the predetermined value and light emission at the time of photographing is unnecessary, the process proceeds to step 105, and the first image sensor 9 is exposed with the exposure amount calculated in step 102. After exposure, the process proceeds to step 109, where the image signal of the first image sensor 9 is subjected to image processing with a white balance coefficient, and the image is stored in a memory (not shown). The white balance coefficient is set so that white paper can be reproduced white under the ambient light having the color temperature of the external light detected in step 102. That is, the gain applied to each color is set so that the RGB output ratio of the first image sensor 9 is 1: 1: 1.

  On the other hand, if the subject brightness is less than the predetermined value and the light emission at the time of photographing is necessary, the process proceeds to step 106, and the main light emission parameter calculation subroutine shown in FIG. 3 is executed to perform the preliminary light emission and calculate the light emission amount of the main light emission. Details of this subroutine will be described later.

  Next, the process proceeds to step 107, where the exposure of the first image sensor 9 is started according to the exposure amount calculated in step 102, and the flash unit 17 performs the main light emission in step 108 during the exposure. In step 109 after shooting, the image signal of the first image sensor 9 is subjected to image processing using a white balance coefficient, and the image is stored in a memory (not shown).

  Next, the calculation process of the main light emission parameter by the preliminary light emission will be described with reference to FIG. In step 201, the color temperature K1 of the external light detected in step 102 of FIG. 2 is set to the color temperature Kx of the preliminary light emission.

  In step 202, it is determined whether or not the light emission efficiency when preliminary light emission is performed at the color temperature Kx is equal to or greater than a predetermined value. The memory (not shown) of the flash unit 17 stores light emission efficiency table data when light is emitted while changing the color temperature. The light emission efficiency corresponding to the color temperature Kx is obtained from the flash unit 17 when the table data is obtained. Search for.

  If the luminous efficiency is less than or equal to the predetermined value, the process proceeds to step 203, and the color temperature Kx during preliminary light emission is changed by ΔK. As a setting method for ΔK, a table of color temperature with high luminous efficiency is stored in advance so that the luminous efficiency becomes a predetermined value or more, and the color temperature closest to the color temperature Kx is selected and changed with reference to the table. ΔK may be set so that the subsequent color temperature Kx becomes the color temperature, or the color temperature Kx after the change is different from the color temperature Kx before the change of the external light every time the processing of step 203 is executed. ΔK may be set so as to alternately shift a predetermined amount toward the high temperature side or the low temperature side.

  If the luminous efficiency is greater than the predetermined value, the process proceeds to step 204, the second image sensor 16 is driven and controlled to start exposure, and preliminary light emission is performed by the flash unit 17 in step 205 during the exposure. The brightness of the object scene is detected based on the image signal.

  In step 206, the image data of the second image sensor 16 obtained by preliminary light emission at the color temperature Kx and the image data of the second image sensor 16 immediately before the preliminary light emission previously stored in the memory (step of FIG. 2). The light emission amount GN1 at the main light emission is calculated based on the above. Note that a method of calculating the main light emission amount based on the preliminary light emission result is known, and detailed description thereof is omitted.

  In step 207, the color temperature K1 of the external light detected in step 102 of FIG. 2 is set to the color temperature Ky of the main light emission.

In step 208, the main light emission amount GN1 is corrected based on the difference between the light emission efficiency of the color temperature Kx during preliminary light emission and the light emission efficiency of the color temperature Ky during main light emission. The corrected main light emission amount GN2 is calculated by the following equation.
GN2 = GN1 + Log ₂ (E (Kx) / E (Ky)) (1)
In the equation (1), the normalized luminous efficiencies when light is emitted at the color temperatures Kx and Ky are E (Kx) and E (Ky), respectively. For example, when the light emission efficiency E (Kx) = 80% during preliminary light emission and the light emission efficiency E (Ky) = 40% during main light emission,
GN2 = GN1 + 1 (2)
It becomes.

  When setting the color temperature of the main light emission amount in step 207 of FIG. 3, the color temperature and the white balance coefficient during the main light emission may be calculated based on the image data at the time of preliminary light emission and non-light emission. . First, the difference between image data at the time of preliminary light emission and at the time of non-light emission is taken. A region with a large difference is a region with a subject that reflects a flash, and is called a foreground here. On the other hand, an area with a small difference is an area where there is no subject that reflects the flash, and is referred to as a background here. For example, the color temperature of the ambient light is calculated based on the ratio of the average values of RGB of the luminance data corresponding to the background area. A table corresponding to the ratio and the color temperature may be stored in the control device 10 in advance. Then, the color temperature of the flash during the main light emission is made substantially equal to the color temperature of the ambient light. The white balance coefficient is set so that white paper under ambient light can be reproduced as white. That is, the gain to be applied to each color is set so that the RGB ratio is 1: 1: 1.

  In the above-described embodiment, the example in which the color temperature of the flash light of the flash unit 17 is adjusted by controlling the current ratio of the three color LEDs 19a to 19c provided in the flash unit 17 has been described. The temperature adjustment method is not limited to the above-described method, and for example, an adjustment method as shown in FIG. 4 can be adopted. In FIG. 4, reference numeral 20 denotes a reflector, and other devices are described with the same reference numerals as those of the device of FIG. 1.

  For example, as shown in FIG. 4A, when a xenon tube 19 'is used as the light emitter, a color filter 21 and a drive mechanism 22 for switching and driving the color filter are provided in front of the xenon tube 19'. As shown in FIG. 4B, the color filter 21 has a plurality of color filters 21a to 21c wound in a roll shape, and rotates the winding spool and the rewinding spool of the driving mechanism 22 so that any color filter is obtained. Can be selected. The illumination control circuit 18 controls the drive mechanism 22 according to the light emission control signal of the control device 10 and selects the color filter 21 corresponding to the color temperature command.

  Instead of the color filter 21 and the drive mechanism 22, as shown in FIG. 4C, a color liquid crystal panel 25 is provided in front of the xenon tube 19 ′, and the illumination control circuit 18 changes the color according to the color temperature command. The color liquid crystal panel 25 may be driven and controlled as described above. In the above embodiment, the color temperature of the main light emission is obtained by measuring the color temperature of the external light by the second imaging sensor. However, the photographer may manually set the color temperature of the main light emission. In step 102, the subsequent calculation may be performed with the color temperature set by the photographer using the color temperature manual setting means (not shown) of the camera body 1 or the flash unit 17 as K1. In this case, since the second image sensor does not necessarily need to acquire color information, it may be a luminance sensor (monochrome sensor).

  As described above, according to the embodiment, since preliminary light emission is performed at a color temperature that is more efficient than main light emission, it is possible to monitor a distant subject while suppressing power consumption, and to obtain an appropriate main light emission amount. Can do.

  Further, according to one embodiment, the color temperature at the time of preliminary light emission is controlled to be a color temperature in the vicinity of the color temperature of the external light and the light emission efficiency of the flash unit 17 is a predetermined value or more. In addition to the effect, it is possible to more accurately calculate the light emission amount during the main light emission based on the preliminary light emission result.

  Furthermore, according to one embodiment, the light emission amount at the main light emission is controlled in consideration of the difference between the light emission efficiency at the color temperature at the preliminary light emission and the light emission efficiency at the color temperature at the main light emission. In addition to the effect, the amount of light emitted during the main light emission can be obtained more accurately.

The figure which shows the structure of one embodiment The flowchart which shows the imaging operation of one embodiment The flowchart which shows this light emission parameter calculation subroutine of one execution form The figure explaining the method of the modification which adjusts the color temperature of a flash

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10; Control apparatus, 16; 2nd imaging sensor, 17; Flash unit, 18; Illumination control circuit, 19, 19 ';

Claims (9)

A flash means for performing preliminary light emission and main light emission when photographing, wherein the color temperature of the light emitter is variable;
A light emission control means for controlling the color temperature of the main light emission based on predetermined information and controlling the color temperature of the preliminary light emission to a color temperature equal to or higher than the light emission efficiency of the main light emission ;
The light emission control means controls the light emission amount of the main light emission in consideration of a difference between the light emission efficiency of the preliminary light emission color temperature and the light emission efficiency of the main light emission color temperature . The camera system according to claim 1,
The camera system according to claim 1, wherein the predetermined information is information relating to a color temperature. The camera system according to claim 1 or 2,
The predetermined information is a color temperature of at least a part of the subject,
A camera system comprising color temperature recognition means for recognizing a color temperature of at least a part of the subject. The camera system according to claim 3.
The camera system according to claim 1, wherein the color temperature recognizing means recognizes the color temperature of external light. The camera system according to claim 4,
The light emission control means controls the color temperature of the preliminary light emission to a color temperature in the vicinity of the color temperature of the external light. In the camera system according to any one of claims 1 to 5,
The light emission control means controls the color temperature of the preliminary light emission to a color temperature at which the light emission efficiency of the preliminary light emission is a predetermined value or more. The camera system according to claim 6 ,
Have a storage means for storing a relationship between the color temperature and luminous efficiency of the light emitter,
The light emission control means uses the relationship between the color temperature of the light emitter and the light emission efficiency stored in the storage means so that the color temperature of the preliminary light emission is equal to or greater than a predetermined value. The camera system is characterized by controlling the color temperature . A camera body comprising the color temperature recognizing means used in the camera system according to claim 3 . Flash device characterized in that it comprises a flash unit for use in a camera system according to any one of claims 1-8.

Images