Photometry device with light and colorimetric sensors

What is claimed is:

1. A photometry device for a camera, comprising: a normal light sensor that performs photometry with respect to an object; an exposure amount determining system that determines an exposure amount of the object in accordance with an output of said normal light sensor; a plurality of colorimetric sensors that detect a color of the object by performing colorimetry with respect to an image of the object which is formed by a photographing lens of the camera, said plurality of colorimetric sensors having spectral sensitivity characteristics that are different from each other; an external light sensor that measures an external light illuminating the object at spectral sensitivity characteristics respectively corresponding to said plurality of colorimetric sensors; a light source color compensation amount determining system that determines light source color compensation amount in accordance with the output of said external light sensor; a light source effect compensation system that compensates for the outputs of said colorimetric sensors with the light source color compensation amount; a colorimetry compensation amount determining system that determines a color of the object based on the output of said calorimetric sensors as compensated by said light source effect compensation system, and then determines a calorimetric compensation amount based on the determined color; an exposure amount compensation system that compensates for the exposure amount determined by said exposure amount determining system in accordance with the colorimetric compensation amount, wherein said light source color compensation amount determining system changes the light source color compensation amount in accordance with an object distance.

2. The photometry device according to claim 1, wherein a predetermined fixed value is used as said light source color compensation amount if the object distance is smaller than a predetermined fixed distance.

3. The photometry device according to claim 2, wherein light source data corresponding to the output of said light source photometry system is stored in a storing system, and wherein said fixed value is obtained in accordance with the data stored in said storing system.

4. The photometry device according to claim 2, wherein a condition where the object distance is smaller than a predetermined fixed distance includes a macro photographing mode of said camera.

5. The photometry device according to claim 1, wherein a value intermediate the light source color compensation amount as determined by the light source color compensation amount determining system and a predetermined fixed value is used as said light source color compensation amount if the object distance is smaller than a predetermined fixed distance.

6. The photometry device according to claim 5, wherein light source data corresponding to the output of said light source photometry system is stored in a storing system, and wherein said fixed value is obtained in accordance with the data stored in said storing system.

7. The photometry device according to claim 5, wherein a condition where the object distance is smaller than a predetermined fixed distance includes a macro photographing mode of said camera.

8. The photometry device according to claim 1, wherein said normal light sensor and said plurality of calorimetric sensors meters light reflected by the object and passed through an optical system of said camera, and wherein said external light sensor receives light which is not passed through the optical system of said camera.

9. The photometry device according to claim 1, wherein said normal light sensor includes a normal light photometry sensor, the spectral sensitivity characteristic of which has a peak sensitivity at a wavelength within a range from 500 nm through 600 nm, wherein said plurality of calorimetric sensors include a blue light photometry sensor for metering blue light component, a green light photometry sensor for metering green light component, and a red light photometry sensor for metering red light component, and wherein said external light sensor includes a photometry sensor having photometry areas for metering blue, green and red light components, respectively.

10. The photometry device according to claim 9, wherein said light source effect compensation system compensates for at least two of the outputs of said calorimetric sensors corresponding to three primary colors of green, blue and red in accordance with the light source color compensation amount.

11. The photometry device according to claim 10, wherein said plurality of colorimetric sensors and said normal light sensor include photometric elements having the same photometric characteristics.

12. The photometry device according to claim 11, wherein said green light sensor is used as said normal light sensor, the output of said green light sensor being used as the output of said normal light sensor.

13. The photometry device according to claim 1, wherein each of said normal light sensor and said plurality of colorimetry sensors has divided photometry areas, said exposure amount determining system and exposure compensation amount determining system determining the exposure amount and the exposure compensation amount in accordance with the output of each of said divided photometry areas.

14. The photometry device according to claim 13, wherein said colorimetric compensation amount determining system judges the color of the object at each of said divided photometry areas, determines the colorimetric compensation amount for each of said divided photometry areas, and determines a colorimetric compensation amount with respect to an entire object based on the colorimetric compensation amounts for said divided photometry areas.

15. The photometry device according to claim 13, wherein said calorimetric compensation amount determining system determines a colorimetric compensation amount for each of said divided photometry areas, and adds a colorimetric compensation amount for each of said photometry areas to the photometry output for each of said divided photometry areas.

16. A photometry device for a camera, comprising: a normal light sensor that performs photometry with respect to an object; an exposure amount determining system that determines an exposure amount of the object in accordance with an output of said normal light sensor; a plurality of calorimetric sensors that detect a color of the object by performing colorimetry with respect to an image of the object which is formed by a photographing lens of the camera, said plurality of calorimetric sensors having spectral sensitivity characteristics that are different from each other; an external light sensor that measures an external light illuminating the object at spectral sensitivity characteristics respectively corresponding to said plurality of colorimetric sensors; a light source color compensation amount determining system that determines light source color compensation amount in accordance with the output of said external light sensor; a light source effect compensation system that compensates for the outputs of said colorimetric sensors with the light source color compensation amount; a colorimetry compensation amount determining system that determines a color of the object based on the output of said colorimetric sensors as compensated by said light source effect compensation system, and then determines a calorimetric compensation amount based on the determined color; an exposure amount compensation system that compensates for the exposure amount determined by said exposure amount determining system in accordance with the calorimetric compensation amount, wherein said light source color compensation amount determining system changes the light source color compensation amount in accordance with a photographing magnification of the photographing lens of said camera.

17. The photometry device according to claim 16, wherein a predetermined fixed value is used as said light source color compensation amount if said photographing magnification exceeds a predetermined photographing magnification range.

18. The photometry device according to claim 17, wherein light source data corresponding to the output of said light source photometry system is stored in a storing system, and wherein said fixed value is obtained in accordance with the data stored in said storing system.

19. The photometry device according to claim 17, wherein a condition where said photographing magnification exceeds a predetermined photographing magnification range includes a macro photographing mode of said camera.

20. The photometry device according to claim 16, wherein a value intermediate between the light source color compensation amount as determined by the light source color compensation amount determining system and a predetermined fixed value is used as said light source color compensation amount if said photographing magnification exceeds a predetermined photographing magnification range.

21. The photometry device according to claim 20, wherein light source data corresponding to the output of said light source photometry system is stored in a storing system, and wherein said fixed value is obtained in accordance with the data stored in said storing system.

22. The photometry device according to claim 20, wherein a condition where said photographing magnification exceeds a predetermined photographing magnification range includes a macro photographing mode of said camera.

23. The photometry device according to claim 16, wherein said normal light sensor and said plurality of calorimetric sensors meters light reflected by the object and passed through an optical system of said camera, and wherein said external light sensor receives light which is not passed through the optical system of said camera.

24. The photometry device according to claim 16, wherein said normal light sensor includes a normal light photometry sensor, the spectral sensitivity characteristic of which has a peak sensitivity at a wavelength within a range from 500 nm through 600 nm, wherein said plurality of colorimetric sensors include a blue light photometry sensor for metering blue light component, a green light photometry sensor for metering green light component, and a red light photometry sensor for metering red light component, and wherein said external light sensor includes a photometry sensor having photometry areas for metering blue, green and red light components, respectively.

25. The photometry device according to claim 24, wherein said light source effect compensation system compensates for at least two of the outputs of said colorimetric sensors corresponding to three primary colors of green, blue and red in accordance with the light source color compensation amount.

26. The photometry device according to claim 25, wherein said plurality of colorimetric sensors and said normal light sensor include photometric elements having the same photometric characteristics.

27. The photometry device according to claim 26, wherein said green light sensor is used as said normal light sensor, the output of said green light sensor being used as the output of said normal light sensor.

28. The photometry device according to claim 16, wherein each of said normal light sensor and said plurality of colorimetry sensors has divided photometry areas, said exposure amount determining system and exposure compensation amount determining system determining the exposure amount and the exposure compensation amount in accordance with the output of each of said divided photometry areas.

29. The photometry device according to claim 28, wherein said colorimetric compensation amount determining system judges the color of the object at each of said divided photometry areas, determines the calorimetric compensation amount for each of said divided photometry areas, and determines a colorimetric compensation amount with respect to an entire object based on the colorimetric compensation amounts for said divided photometry areas.

30. The photometry device according to claim 28, wherein said colorimetric compensation amount determining system determines a colorimetric compensation amount for each of said divided photometry areas, and adds a calorimetric compensation amount for each of said photometry areas to the photometry output for each of said divided photometry areas.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

The present invention relates to a photometry device applicable to an SLR (Single Lens Reflex) camera, and more particularly to a photometry device with which exposure errors due to a difference of reflectivity of objects having different colors can be compensated.

Recently, in most of cameras, reflection type photometry devices are employed. The reflection type photometry device receives the light, which is reflected by an object and passed through an observing optical system of a camera, using a light receiving element, determines the brightness of the object based on the output of the measured value, and then calculates the exposure value of the camera based on the measured brightness. However, this type of the photometry device cannot detect the color of the object because of its structure. Accordingly, in such a device, the reflectivity of an object is generally assumed to be 18% and the exposure parameter is determined on this assumption. Therefore, regarding a whitish object whose reflectivity is greater than 18%, the determined brightness is greater than the actual brightness. If the camera controls an exposure operation based on the determined exposure value, the object is under exposed. A dark object whose reflectivity is less than 18% is measured to have a lower brightness. Therefore, such an object is over exposed. The difference of the reflectivity of the object may also occur depending on the color of the object.

For example, when the color of an object is yellow, the reflectivity maybe up to 70%. In such a case, if the standard reflectivity is assumed to be 18%, the exposure value is approximately 2 Ev lower than necessary. If the object color is blue, the reflectivity is approximately 9%. In this case, the object is over exposed by approximately 1 Ev greater than necessary.

Therefore, in the conventional photometry device, the photographer is required to guess the reflectivity of the object. Then, based on the reflectivity determined by the photographer, the exposure is controlled such that, if the object is a whitish or yellowish one having a relatively high reflectivity, it is to be overexposed, and if the object is a blackish or bluish one having a relatively low reflectivity, it is to be underexposed. With this operation, the above-described defects may be solved.

However, accurately guessing the reflectivity of the object and controlling the exposure can be done only by experienced and skilled photographers. It is impossible to require all the photographers to do such an operation. Further, it is not preferable that a manual operation of the photographer is required for exposure. Further, if such a manual operation is required, cameras become unsuitable for the recent trend of automatic photographing.

It may be possible to measure the color of the object, and perform exposure compensation based on the reflectivity corresponding to the measured color. If such a control is performed, an appropriate exposure value seems to be obtained automatically regardless of the color of the object. To perform such an operation, a plurality of photometry sensors for performing colorimetry may be provided inside the camera for selectively measuring different portions of the object, and a so-called TTL colorimetry may be performed. That is, light passed through a photographing lens of the camera is received by the plurality of sensors.

When such a structure is adopted, however, the spectral reflection characteristics of the object and the spectral radiant characteristic of an external light source are overlapped when the colorimetry is performed. Therefore, due to the spectral radiant characteristics of the external light source illuminating the object, it becomes difficult to measure the object color accurately. Then, the compensation amount of the exposure value includes errors, and the appropriate exposure may not be achieved.

It may be possible to measure the spectral radiant characteristic of the external light source independently, and compensate for the colorimetry result using the spectral radiant characteristic of the external light source. However, depending on photographing conditions, the spectral radiant characteristic of the external light source may not be measured accurately. For example, when a photographing magnification is relatively large, or a distance between the camera and an object is relatively small, as in a macro photographing, the light reflected by the object is also received by a photometry system for the external light source. In such a case, the colorimetry result cannot be compensated for correctly, and therefore, the appropriate exposure amount may not be determined.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved photometry device which optimizes the effectiveness of a light source compensation value, which is obtained based on the spectral radiant characteristic of an external light source, in accordance with a photographing condition, so that an exposure compensation amount is calculated in accordance with the colorimetric compensation value, and thereby appropriate exposure values can be obtained regardless of a difference of photographing conditions as well as the reflectivity of the object.

For the above object, according to the invention, there is provided a photometry device for a camera, which is provided with a normal light sensor that performs photometry with respect to an object, an exposure amount determining system that determines an exposure amount of the object in accordance with an output of the normal light sensor, a plurality of colorimetric sensors that detect a color of the object by performing colorimetry with respect to an image of the object which is formed by a photographing lens of the camera, the plurality of colorimetric sensors having spectral sensitivity characteristics that are different from each other, an external light sensor that measures an external light illuminating the object at spectral sensitivity characteristics respectively corresponding to the plurality of colorimetric sensors, a light source color compensation amount determining system that determines light source color compensation amount in accordance with the output of the external light sensor, a light source effect compensation system that compensates for the outputs of the colorimetric sensors in accordance with the light source color compensation amount, a colorimetry compensation amount determining system that determines a color of the object based on the output of the colorimetric sensors as compensated by the light source effect compensation system, and then determines a colorimetric compensation amount based on the determined color, an exposure amount compensation system that compensates for the exposure amount determined by the exposure amount determining system in accordance with the colorimetric compensation amount. In such a device, the light source color compensation amount determining system changes the light source color compensation amount in accordance with an object distance.

Alternatively, the light source color compensation amount determining system changes the light source color compensation amount in accordance with the magnification of the photographing lens.

Optionally, a predetermined fixed value is used as the light source color compensation amount if the photographing magnification exceeds a predetermined photographing magnification range or the object distance is smaller than a predetermined fixed distance.

Further optionally, a value intermediate the light source color compensation amount as determined by the light source color compensation amount determining system and a predetermined fixed value is used as the light source color compensation amount if the photographing magnification exceeds a predetermined photographing magnification range or the object distance is smaller than a predetermined fixed distance.

Further, the light source data corresponding to the output of the light source photometry system is stored in a storing system, and the fixed value is obtained in accordance with the data stored in the storing system.

Still optionally, a condition where the photographing magnification exceeds a predetermined photographing magnification range or the object distance is smaller than a predetermined fixed distance includes a condition where the camera operates in a macro photographing mode.

Further optionally, the normal light sensor and the plurality of colorimetric sensors meters light reflected by the object and passed through an optical system of the camera, and wherein the external light sensor receives light which is not passed through the optical system of the camera.

Furthermore, the normal light sensor includes a normal light photometry sensor, the spectral sensitivity characteristic of which has a peak sensitivity at a wavelength within a range from 500 nm through 600 nm, the plurality of colorimetric sensors include a blue light photometry sensor for metering blue light component, a green light photometry sensor for metering green light component, and a red light photometry sensor for metering red light component, and the external light sensor includes a photometry sensor having photometry areas for metering blue, green and red light components, respectively.

In this case, the light source effect compensation system may compensate for at least two of the outputs of the colorimetric sensors corresponding to three primary colors of green, blue and red in accordance with the light source color compensation amount.

Further, the plurality of calorimetric sensors and the normal light sensor may include photometric elements having the same photometric characteristics.

In this case, the green light sensor may be used as the normal light sensor, the output of the green light sensor being used as the output of the normal light sensor.

Optionally, each of the normal light sensor and the plurality of colorimetry sensors has divided photometry areas, the exposure amount determining system and exposure compensation amount determining system determining the exposure amount and the exposure compensation amount in accordance with the output of each of the divided photometry areas.

In this case, the colorimetric compensation amount determining system may judge the color of the object at each of the divided photometry areas, determine the colorimetric compensation amount for each of the divided photometry areas, and determine a colorimetric compensation amount with respect to an entire object based on the calorimetric compensation amounts for the divided photometry areas.

Alternatively, the colorimetric compensation amount determining system may determine a calorimetric compensation amount for each of the divided photometry areas, and add a colorimetric compensation amount for each of the photometry areas to the photometry output for each of the divided photometry areas.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 shows a perspective view of a camera employing a photometry device according to the invention;

FIG. 2 schematically shows main components of the camera shown in FIG. 1;

FIG. 3A shows an arrangement of photometry sensors;

FIG. 3B shows an alternative arrangement of photometry sensors;

FIG. 4A schematically shows a structure of each of the photometry sensors;

FIG. 4B shows a relationship between the photometry areas of each photometry sensor;

FIGS. 5A-5D show a structure of a photometry sensor for a light source, and photometry and colorimetry sensors;

FIG. 6 shows spectral sensitivity characteristics of the green, blue and red light sensors;

FIG. 7 shows a block diagram of main portions of the camera;

FIG. 8 is a flowchart illustrating a main procedure of a photometry operation according to an embodiment;

FIG. 9 is a flowchart illustrating the "lens communication procedure";

FIG. 10 shows a flowchart illustrating the "photometry sensor Bvd calculation procedure";

FIG. 11 is a flowchart illustrating the "open aperture photometry compensation calculation procedure";

FIG. 12 is a flowchart illustrating an "exposure value calculation procedure";

FIG. 13 is a flowchart illustrating a "colorimetry procedure";

FIG. 14 is a flowchart illustrating an "external light source effectiveness determination" procedure;

FIGS. 15A-15C show tables indicating photographing magnification, focal lengths, photographing distances (object distances) and corresponding APEX values;

FIGS. 16 and 17 show a flowchart illustrating the "light source compensation procedure";

FIG. 18 is a flowchart illustrating the "light source difference compensation procedure";

FIGS. 19A-19F show exemplary spectral sensitivity characteristics of photometry sensors 9B, 9G and 9R;

FIG. 20 is a flowchart illustrating the "colorimetric parameter calculation procedure";

FIG. 21 is a flowchart illustrating the "colorimetric constant setting procedure";

FIG. 22 shows an example of constants read from the EEPROM;

FIGS. 23 and 24 show a flowchart illustrating the "color judgment procedure";

FIG. 25 shows an example of the "area colorimetric compensation value calculation procedure"; and

FIG. 26 is a flowchart illustrating a "CC calculating procedure", which is called at S28 of the main procedure.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, referring to the accompanying drawings, an embodiment according to the present invention will be described.

FIG. 1 shows a perspective view of a camera 1000 employing a photometry device according to the invention, and FIG. 2 schematically shows main components of the camera 1000.

The camera 1000 has a camera body 1, to which a photographing lens 2 is detachably coupled. The camera body 1 accommodates a quick return mirror 3, a focusing glass 4, a pentagonal prism 5 (or a pentagonal mirror), and an eyepiece optical system 6. A part of the quick return mirror 3 is formed to be a half mirror 3a (see FIG. 1), and behind the half mirror 3a, an auxiliary mirror 7 is provided. Light passed through the half mirror 3a is reflected by the auxiliary mirror 7, and is directed toward a distance measuring device 8.

The distance measuring device 8 is used for an AF (Automatic focusing) control. On the rear side of the pentagonal prism 5, four photometry sensors 9 (9D, 9R, 9G and 9B) are provided (see FIGS. 1 and 2), each of which functions as a photometry element and receives part of light passed through the photographing lens 2. Based on the outputs of the photometry sensors 9, a photometry operation for determining exposure parameters is executed. On an upper front portion of the camera body 1, a window 1a is formed, and a photometry sensor 12 for receiving light passed through the window 1a is provided, with a milky-white diffusing plate 13 being located therebetween. The external light entered through the window 1a is diffused by the diffusing plate 13 and measured by the photometry sensor 12.

The photographing lens 2 and the camera body 1 are electrically connected through electrical contacts 10. Thus, a lens ROM 11 built in the photographing lens 2 is electrically connected to a control circuit 20 accommodated in the camera body 1. On an outer surface of the camera body 1, an LCD (liquid crystal display) 21, and various buttons such as a release button 22 are provided. Furthermore, inside the camera body 1, various mechanisms such as a film winding mechanism are provided. However, such mechanisms are conventionally known, and description thereof will be omitted for the sake of the simplicity.

FIG. 3A shows a rear view of the pentagonal prism 5. As shown in FIG. 3A, the four photometry sensors 9 includes sensors 9D and 9G provided at an upper central portion on the eyepiece side of the pentagonal prism 5, and sensors 9B and 9R provided at lower side portions on the eyepiece side of the pentagonal prism 5. The photometry sensors 9D, 9G, 9B and 9R are mounted on an FPC (flexible printed circuit board) 91 and fixedly positioned at the above-described respective positions by the FPC 91. In front of (i.e., on the pentagonal prism side of) each of the photometry sensors 9D, 9G, 9B and 9R, a collective lens 92 is provided to form an object image on each of the sensors 9D, 9G, 9B and 9R.

FIG. 4A schematically shows a structure of each of the sensors 9D, 9G, 9B and 9R. As shown in FIG. 3A, each sensor 9 (9D, 9G, 9B or 9R) is constructed as a planar structure photometry IC chip that is configured such that a light receiving section and an amplifier AMP are integrally formed. The light receiving section includes six photometry areas, i.e., a central area A0, a left area A1, a right area A2, an upper area A3, a lower area A4, and a peripheral area A5.

FIG. 4B shows a relationship between the photometry areas A0-A5 and portions of an object. The photometry areas A0-A5 of each sensor receives the light from respective portions of an object as indicated in FIG. 4B. The photometry sensor 9G is provided with a green filter GF on its light receiving surface (see FIG. 5B), and receives a green component of light, the photometry sensor 9B is provided with a blue filter BF on its light receiving surface (see FIG. 5C), and receives a blue component of light, and the photometry sensor 9R is provided with a red filter RF on its light receiving surface (see FIG. 5D), and receives a red component of light. In this embodiment, the three sensors 9G, 9B and 9R are used as colorimetry elements. Spectral sensitivity characteristics of the sensors 9G, 9B and 9R respectively provided with the green, blue and red filters GF, BF and RF are indicated in FIG. 6. The sensors 9G, 9B and 9R have peaks in sensitivity at approximately 530 nm, 420 nm, and 630 nm, respectively. The remaining sensor 9D is not provided with a color filter. It should be noted, however, that the spectral sensitivity characteristic of the sensor 9D has its peak within a wavelength range of 500-600 nm, which is close to the visual sensitivity characteristic. The sensor 9D is used as a normal light detecting sensor.

As shown in FIG. 5A, the photometry sensor 12 is formed of the same IC chip as the sensors 9. Among the photometry areas A0-A5 of the photometry sensor 12, however, only the areas A0, A1 and A2 are used. Further, a green filter GF is provided in front of the area A0, a blue filter BF is provided in front of the area A1, and a red filter RF is provided in front of the area A2. The filters GF, BF and RF provided to the photometry sensor 12 have the same spectral transmissivity characteristics as the filters provided to the photometry sensors 9G, 9B and 9R, respectively. With this configuration, the areas A0, A1 and A2 of the photometry sensor 12 receive green, blue and red components of the external light illuminating the object, respectively. Since all the photometry sensors are formed of the same IC chip, the spectral sensitivity, output characteristics and the like are substantially the same. Further, since the same IC chip is used, manufacturing cost can be reduced. Further, since the same filters are used for the areas A0-A2 of the photometry sensor 12 and the photometry sensors 9G, 9B and 9R, respectively, the spectral sensitivity characteristics of these sensors are substantially identical, respectively.

FIG. 7 shows a block diagram of main portions of the camera 1000. The four sensors 9D, 9G, 9B and 9R output values indicative of quantity of received light (components) to the controller 20, respectively. From the photometry sensor 12, photometry values for green, blue and red components of the external light are output. Further, the output (i.e., a distance value) of the distance measuring device 8 is input to the controller 20, which controls the AF device 25 to perform the automatic focusing operation.

Furthermore, the controller 20 is connected with a photometry switch SWS and a shutter-release switch SWR. The photometry switch SWS is ON when the release button 22 is half depressed. The shutter-release switch SWR is ON when the shutter button is fully depressed. When the shutter button is depressed halfway and the photometry switch SWS is turned ON, the controller 20 performs a photometry calculation in accordance with a predetermined algorithm, and calculates an exposure value. Then, the controller 20 controls the exposure control device 23 in accordance with the calculated exposure value to perform a photographing operation. Further, the controller 20 drives a display driver 24 to display the calculated exposure value on the LCD pane 121. It should be noted that the controller 20 includes an EEPROM 26 storing various values necessary for the photometry calculation (which will be described in detail later), and a RAM 27 for temporarily storing various pieces of data.

An operation of the photometry device will be described hereinafter.

FIG. 8 is a flowchart illustrating a main procedure of a photometry operation. When the release button 22 is half depressed and the photometry switch SWS is ON (S11: YES), a "lens communication procedure" is performed (S12) so that the controller 20 receives data intrinsic to the photographing lens 2 currently mounted onto the camera body 1. Specifically, the data intrinsic to the photographing lens 2 includes an open f-number, a focal length of the photographing lens 2 and the like, which may affect the photometry calculation. The data is transmitted from a lens ROM 11 of the photographing lens 2 to the controller 20 through the electrical contacts 10. Then, a "photometry sensor output Bvd calculation procedure" is executed (S13). In this procedure, the photometry sensors 9 (9D, 9G, 9B and 9R) output analog photometry values which are obtained by receiving light through the photographing lens 2, the quick return mirror 3, and the pentagonal prism 5. Then, the analog values are converted into digital brightness values Bvd which can be used in the operation executed by the controller 20. Then, based on the brightness value Bvd obtained at S13 and the lens data intrinsic to the photographing lens 2 retrieved at S12, an "open aperture photometry compensation calculation procedure" is executed (S14) to compensate for errors depending on individual photographing lenses.

At S15, an "exposure value calculation procedure" is executed. In this procedure, based on the brightness value Bvd, which is obtained in accordance with the output of the photometry sensor 9D for normal light, an exposure value Lvd is calculated. In this procedure, parameters for calculating the exposure value Lvd in accordance with photographing conditions, e.g., a rear light condition, a magnification and/or scene of photographing, are obtained. Then, based on the parameters, the exposure value Lvd is calculated.

At S16, based on the brightness value Bvd obtained by each of the sensors 9R, 9B and 9G for the RGB (Red, Green and Blue) color components and the brightness values obtained by the photometry sensor 12, a "colorimetry procedure" is executed. Specifically, based on the brightness values output by the photometry sensor 12, compensation values for compensating errors of the output values of the sensors 9R, 9B and 9G due to the color of the external light are determined. Then, based on the compensation values, the brightness values Bvd obtained by the photometry sensors 9R, 9G and 9B are compensated. Then, based on the compensated brightness values Bvd, the color of the object is determined, and a colorimetric compensation value CC is calculated based on the determined color of the object. In S17, an "exposure value colorimetric compensation procedure" is executed, where the exposure value Lvd obtained at S15 is compensated based on the calorimetric compensation value CC.

At S18, if the shutter-release switch SWR is ON (S18: YES), the exposure control device 23 controls the exposure operation at S20 in accordance with the exposure value Lvd obtained at S17 to execute a photographing operation. If the shutter-release switch SWR is OFF, controls goes to S19, where it is detected whether a photometry timer is OFF.

If the photometry timer is ON (i.e., if a predetermined period has not elapsed) (S19: NO), control proceeds to S12, and the foregoing procedures are repeated. If the photometry timer is OFF (i.e., if the predetermined period has elapsed) (S19: YES), control proceeds to S11.

FIG. 9 is a flowchart illustrating the "lens communication procedure", which is called at S12 of the main procedure shown in FIG. 8.

In the lens communication procedure, the controller 20 accesses the lens ROM 11 through the electrical contacts 10, and reads the data intrinsic to the photographing lens 2 stored in the lens ROM 11 (S101). The data is stored in the RAM 27 of the controller 20, and control returns. Items included in the data intrinsic to the photographing lens 2 include, for example, a lens type, lens data, the shortest focusable distance, a focusable range, a focal length of the photographing lens, an exit pupil position, an open f-number, an aperture efficiency and the like. In this embodiment, the controller 20 reads the data from the ROM 11 and stores the same in the RAM 27.

FIG. 10 shows a flowchart illustrating the "photometry sensor Bvd calculation procedure", which is called at S13 in the main procedure shown in FIG. 8.

In this procedure, data Bvad(i) (where, i=0, 1, . . . , 5) which represents A/D converted output voltages (analog data) of the photometry areas Ai (i=0, 1, . . . , 5) shown in FIG. 4A of the photometry sensor 9D for normal light are obtained. Further, data Bvad.multidot.g(i), Bvad.multidot.b(i) and Bvad.multidot.r(i) which represent A/D converted values of the output voltages of the photometry areas Ai (i=0, 1, 2, . . . 5) of each of the sensors 9G, 9B and 9R for color components are obtained. Then, the A/D converted values Bvad(i) of the sensor 9D output are adjusted to brightness values Bvd(i) (S111). The A/D converted values Bvad.multidot.g(i), Bvad.multidot.b(i) and Bvad.multidot.r(i) (i=0, 1, 2, . . . 5) are also adjusted to the brightness values Bvd.multidot.g(i), Bvd.multidot.b(i) and Bvd.multidot.r(i), respectively (S112). Further, the A/D converted values Bvad.multidot.wb(i) (where i=0, 1 and 2), which represent the outputs from the areas A0-A2 of the photometry sensor 12, respectively, are adjusted to the brightness values Bvd.multidot.wb(i), respectively (S113).

FIG. 11 is a flowchart illustrating the "open aperture photometry compensation calculation procedure" which is called at S14 of the main procedure shown in FIG. 8.

At S121, an open aperture photometry compensation value Mnd1(i) is calculated based on the focal length, the exit pupil position, the open f-number and the aperture efficiency stored in the RAM 27. Compensation values mv1, mv2, mv3 and mv4 for compensating for shift amounts with respect to the reference photometry values due to the individual differences of the optical characteristics of the cameras, and the focal length, the exit pupil position, the open aperture and the aperture efficiency, are determined. Then, the sum of the compensation values mv1+mv2+mv3+mv4 is obtained, which is referred to as the open aperture compensation value Mnd1(i). Following the similar procedure, the open aperture compensation values Mnd1.multidot.g(i), Mnd1.multidot.b(i), and Mnd1.multidot.r(i) are calculated. Then the open aperture compensation value Mnd1(i) is added to the brightness value Bvd(i), and then the sum is determined as a new brightness value Bvd(i). Thus, the following calculation is executed at S121:

Similar to the above, with respect to the brightness values Bvd.multidot.g(i), Bvd.multidot.b(i) and Bvd.multidot.r(i) obtained by the photometry sensors 9G, 9B and 9R, open aperture photometry compensation values Mnd1.multidot.g(i), Mnd1.multidot.b(i) and Mnd1.multidot.r(i) are added to obtain newly defined brightness values (S122). That is:

As a result, each brightness value is free from the affect of the individual differences of photographing lenses 2 when coupled to the camera body 1.

FIG. 12 is a flowchart illustrating an "exposure value calculating procedure", which is called at S15 of the main procedure.

In the "exposure value calculating procedure", the brightness values Bvd(i) are compensated in accordance with a photographing condition to obtain an appropriate exposure value Lvd. Specifically, in the "exposure value calculating procedure", the brightness values Bvd(i) (where i=0-5) corresponding to the photometry areas A0-A5 are compared with each other, or the brightness of the object as a whole is detected, and a condition of the object to be photographed (e.g., photographing with rear light, photographing at dusk, or photographing at night) is determined. Then, based on the determined condition, the brightness values Bvd(i) are weighted, or one of the brightness values Bvd(i) is selected and then the exposure value Lvd suitable to the photographing condition is determined. Then, based on the brightness values Bvd(i), parameters for calculating the exposure value Lvd are calculated at S131. Then, the upper brightness limit of a parameter is calculated (S132), compensation value for the rear light is calculated (S133), weighting parameters are calculated (S134), a photographing magnification M is checked (S135), a photographing scene is judged (S136), a positive compensation value for a high brightness photographing scene is calculated (S137), and the exposure value Lvd is calculated based on the calculated parameters and the brightness values Bvd(i) (S138).

FIG. 13 is a flowchart illustrating a "colorimetry procedure" called at S16 of the main procedure.

In the "colorimetry procedure", the color of the object is detected, and a calorimetric compensation value CC is calculated in accordance with the detected color of the object.

At S20, colorimetric parameters are initialized (i.e., set to initial values). Depending on the color temperature of a light source illuminating the object, the calorimetric value varies. In S21, an "external light source effect examining procedure" is executed to determine the degree of effects of the external light source with respect to an object. Since the colorimetry results may differ depending on the color tempe