FR2783613A1 - Automatic control of exposure on cameras by combining luminosity data from a photometer with color data from a colorimeter and measured distances to a point in the picture frame - Google Patents

Abstract

A reflex camera (1) with object lens (2) has a mirror (3) with inset half mirror (3a) which allows light to reach a distance measuring unit (8) via a third mirror (7). Three photometers (9R,9G,9B) on the pentaprism (5) have red green and blue filters which enable them to produce color data and a fourth photometer (9D) produces luminosity data. An exposure calculator for a sighted point uses the color data to correct exposures based on luminosity

Description

The invention relates to a camera

  provided with a photometry device.

  Recently, cameras have been fitted with photometric devices for automatic exposure adjustment. In particular, a photometry device widely used in a camera for taking

  views is a reflection type photometry device.

  It is designed to receive light reflected by an object through an optical observation system of a camera and to measure an amount of light using a photosensitive element to detect the brightness of the object. . Based on the brightness of the object thus detected, an exposure value (commonly known as the Ev value) is determined and then, in accordance with a predetermined algorithm, exposure parameters (i.e. say a shutter speed and a

  aperture value) are determined.

  However, this type of photometry device does not detect the reflection factor of an object and, therefore, the exposure value and therefore the exposure adjustment parameters are calculated assuming that the light reflection factor is a fixed value and

predetermined, for example 18%.

  Therefore, when an object is a whitish subject with a light reflectance greater than 18%, the brightness is detected as being greater than it really is and such an object tends

  therefore to be photographed in an underexposed state.

  When an object is a dark object with a light reflection factor of less than 18%, its brightness is detected as being less than the actual brightness and such an object therefore tends to be photographed in a state

overexposure.

  To avoid the above defects, there is known a camera provided with an exposure compensation unit. In such a camera, a photographer can change the exposure value in order to take a photograph in a slightly overexposed state when a whitish subject is to be photographed and, in the case of a dark object, the photographer can change the exposure value to take a photograph in a slightly underexposed state. By carrying out such an exposure operation with modification of the exposure value, it is possible to eliminate

the above problems.

  However, differences in the light reflectance of the object also appear due to differences in the colors of the object. For example, a yellow object, with a relatively high light reflection factor, tends to be photographed in a slightly underexposed state, and a blue object, with a relatively low light reflection factor,

  tends to be photographed in a slightly overexposed state.

  Therefore, to make an exposure correction taking into account the color differences of the object, the photographer must be aware of a relationship between the color and the reflectivity of the light of the object to optimize the value d using the exposure compensation unit. However, it is virtually impossible to ask photographers to do such exposure compensation. In addition, if such a correction operation is necessary, the cameras become incapable of taking automatic shots. It is therefore an object of the invention to provide a camera provided with an improved exposure correction unit which automatically corrects exposure parameters in order to allow shots to be taken in an optimal exposure state independently. differences in the color of objects. To achieve the above object, in accordance with the invention, there is provided a camera which is provided with: a photometry device used to detect the brightness of an object; a colorimetric device which detects a color of the object; and a controller that determines an exposure value based on the output signal from the photometry device, the controller compensates for the exposure value based on the color of the object

  detected by the colorimetric device.

  Since the exposure value is compensated based on the result of the photometry and the result of the colorimetry, a value can be obtained

optimized exposure.

  The control device includes optional

  a storage device which stores several compensation values corresponding to several colors, and the control device compensates the exposure value by adding a compensation value, stored in the storage device, corresponding

to the color of the object.

  The compensation values are stored in memory and are referred to after the color has been determined. The compensation values can be corrected relatively easily, and there is no need to modify the algorithm intended to

  determine the correction value.

  The camera may further optionally include a distance measuring device which detects a distance from the object at a predetermined point within a photography frame, the photometric device detects the brightness of the object in an area, inside the photography frame, which includes the predetermined point, and the colorimetric device detects the color of the object in an area, inside the photography frame, which includes point

predetermined.

  Since the distance measurement point, and a target point relative to which the photometry and colorimetry operations are performed, correspond to each other, the exposure value can

  be optimized based on the photographer's intention.

  Alternatively, the camera may include a distance measuring device capable of detecting a distance from the object at several distance measuring points defined within a photographic frame of the camera. Shooting. In this case, the photometry device may be able to detect the brightness of the object in any of the areas within the photograph frame, which respectively include the plurality of distance measurement points, and the A colorimetric device may be able to detect the color of the object in any of the areas, inside the photo frame, which respectively comprise the plurality of distance measurement points. The distance of the object can be detected with respect to one, chosen, of the plurality of distance measurement points, the exposure value being detected in an area corresponding to the point chosen from the plurality of measurement points of distance, and the color of the object being detected in an area corresponding to the point chosen from among the plurality of

distance measurement points.

  It is also optional that the colorimetry device can comprise: several photometric elements intended to measure a quantity of received light having different ranges of wavelengths; and a color determination system which determines the color based on the amount of light values

  detected by photometric elements.

  According to another aspect of the invention, there is provided an exposure adjustment device for a camera, which comprises: a photometry device which is used to detect the brightness of an object; a colorimetric device which detects a color of the object; and a controller that determines an exposure value based on the output signal from the photometry device, the controller compensates for the exposure value based on the color of the object detected by the colorimetry device. The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which: FIG. 1 is a cross section schematically showing an arrangement of an optical system of a camera according to a embodiment of the invention; Figure 2A schematically shows a structure of a distance measurement system used in the camera shown in Figure 1; Figure 2B shows an arrangement of photometry elements; FIG. 2C shows another arrangement of the photometry elements; Figure 3A shows distance measurement points of each of the distance measurement systems shown in Figure 2A; FIG. 3B shows areas for measuring the brightness of each of the photometry elements shown in FIG. 2B or 2C; Figure 4 is a graph showing the spectral transmission characteristics of color filters provided on the photometry elements shown in Figure 2B or 2C; Figure 5 is a simplified block diagram of a main part of a control device of the camera; Figure 6 is a flow chart for illustrating the exposure adjustment operations; Figures 7A and 7B are graphs showing output signals from the photometry elements; and Figures 8, 9, 10 and 11 shows a flow diagram illustrating a colorimetric operation in accordance with a

  embodiment of the invention.

  Figure 1 schematically shows a cross-sectional view of a camera 100 to which the invention can be applied. The camera 100 is a single-lens reflex camera having a body 1, a camera lens 2 detachably mounted on the body 1, a mirror 3 with rapid return, a plate 4 focusing, a pentaprism (or pentamirror) 5 and an optical system with eyepiece 6. A part of the mirror 3 with rapid return is produced in the form of a half-mirror 3a. Part of the light passing through the photography objective 2 passes through the half-mirror 3a, is reflected by a

  mirror 7 and falls on a distance detection unit 8.

  Four photometric elements 9D, 9R, 9G and 9B are arranged on the pentaprism 5 at four points on the

  surface 5A facing the eyepiece optical system 6.

  Each of the photometric elements 9D, 9R, 9G and 9B is arranged so as to receive part of the light

from an object.

  FIG. 2A schematically shows a structure of the distance measuring unit 8. The distance measurement unit 8 is a distance measurement unit at several points, of the passive type, which is formed to detect distances from objects at three points inside a photographic frame: a central position PC, a left position PL and a right position PR (see Figure 3A). Dual type lenses 10C, 10L and 10R are provided to receive light corresponding to the points PC, PL and PR. In addition, a position detection device (PSD) 11 is provided for receiving light having passed through the lenses 0lC, 10L and 10R of the double type. On the basis of the output signal of the device 11, object distances corresponding to the points PC, PL and PR are detected. An example of such a distance measuring unit is described in the United States patent

of America N 5 397 887.

  The photometric elements 9D and 9R arranged at upper parts of the lateral surface 5A of the eyepiece optical system of pentaprism 5, and the photometric elements 9G and 9B are arranged at lower parts of the surface 5A of pentaprism 5 as

shown in Figure 2B.

  It should be noted that the arrangement of the photometric elements 9D, 9R, 9G and 9B shown in FIG. 2B is intended to use an excess area in a viewfinder frame. According to the arrangement shown in Fig. 2B, a light receiving surface of each photometric element can be enlarged and the amount of light reception can be increased. If it is not necessary for the quantity of light to be as large, the photometric elements 9D, 9R, 9G and 9B can be produced in a space-saving form and

  grouped in a part as shown in Figure 2C.

  Each of the photometric elements 9D, 9R, 9G and 9B is provided with an image forming lens and is configured to receive light from more than one area. In particular, as shown in FIG. 3B, a lens area (which corresponds to the photo frame) is divided into nine areas: a central area AC; a left central zone AL; a right central zone AR; an upper zone AU; a lower zone AD; an upper left ALU area; an upper right ARU area; a lower left area ALD; and a lower right ARD area. Each of the photometric elements 9D, 9R, 9G and 9B is configured to detect the brightness of the nine zones. For this purpose, each photometric element can be produced in the form of a photodiode (for example that known as being of the planar type) having nine zones

  separate light reception.

  The three distance measurement points PC, PL and PR are arranged to be included in the three zones

  light reception AC, AL and AR, respectively.

  In addition, the photometric element 9B is provided with a blue filter; the photometric element 9G is provided with a green filter; and the photometric element 9R is provided with a red filter. The photometric element 9D is not provided with a color filter. The spectral transmission properties of the blue, green and red filters provided to the respective photometric elements 9B, 9G and 9R are shown in Figure 4. As shown in Figure 4, the blue, green and red filters have maximum wavelengths of transmission which are respectively about

420 nm, 530 nm and 630 nm.

  Figure 5 is a simplified block diagram showing a main part of a control device of the camera 100. The photometric elements 9R, 9G and 9B constitute a colorimeter 12 and output signals representing photometric values respective color components to a control device 20. The photometric element 9D is used as an independent photometry device 13 which outputs the photometric values measured to the control device 20. The output signal from the unit 8 distance measurement at several points is also transmitted to the control device 20 as the detected distance value. The state of a photometric switch SWS and a shutter release switch SWR is detected by the control device 20. The photometric switch SWS is closed in response to a half press of a button. camera 100 trips, and the shutter-release SWR switch is closed in response to being pressed

  complete with release button.

  When the photometry switch SWS is closed, on the basis of the output signals from the colorimeter 12, the photometer 13 and the unit for measuring distance at several points, in accordance with a predetermined algorithm, the control device 20 attacks an autofocus unit (AF) 14 and an exposure adjustment unit 15. The controller 20 also controls the display driver 16 to display the distance value and the photometric value on a liquid crystal display (LCD) 17. It should be noted that the control device 20 comprises a memory 21 intended for the storage of correction values

  photometric AEV, which will be described below.

  A photographing operation of the camera 100 will be described with reference to the flowcharts. FIG. 6 is a main flowchart illustrating the photography operation performed by the camera 100. When the trigger button of the camera is half pressed and the photometry switch SWS is closed, the distance measuring unit 8 at several points executes

  distance measurement of an object (S102).

  When the camera 100 operates in a manual distance measurement mode, one of the three distance measurement points PC, PR or PL is selected by a photographer. The distance measurement point can be selected by actuating an operating element provided on the camera 100. In this case, the control device 20 receives from the distance measurement unit 8 the corresponding output signal at the selected distance measurement point and, based on the received signal, the controller 20 determines a drive value of the AF automatic focusing unit 14, and drives the AF unit 14 to perform an operation autofocus, whereby the photographic lens 2 is placed in a position in which it is in focus on an object in focus

  distance measuring device selected.

  When the camera 100 operates in an automatic distance measurement mode, the control device 20 receives, from the distance measurement unit 8 at several points, the signal corresponding to a target point which is determined to be advance according to the predetermined algorithm. The target point can be, for example, a point corresponding to the shortest object distance. The control device 20 then performs a focusing operation (that is to say drives the photographic objective 2) to focus on the object located at the target point. An example of the algorithm for determining the target point is described

  in U.S. Patent No. 4,882,601.

  Then, in a step S103, the control device 20 receives, among the photometric values measured by each of the four photometric elements 9D, 9R, 9B and 9G, a value corresponding to one of the zones

  photometric AC, AR and AL containing the target point (i.e.

  i.e. the point determined from the distance measurement points PC, PR and PL), which are selected / determined in S102. Next, in a step S104, an exposure value EV 'is determined as a function of the photometric value detected by the photometer 13 (that is to say the photometric element 9D) which is not provided with a color filter . This exposure value EV 'is a value obtained when the reflection factor of the subject is

assumed to be 18%.

  Then, in step S105, a colorimetric process is executed. Namely, the control device 20 receives, among the photometric values of each of the photometric elements 9R, 9G and 9B, which are provided with color filters, the photometric values corresponding to the photometric zone containing the target point (i.e. - say the point selected from the PC, PR or PL distance measurement points), which is selected in S102. Then, by a comparison of the photometric values of the photometric elements 9R, 9G and 9B, the light coming from the object located at the distance measurement point is subjected to a spectral analysis, and the color of the object at the targeted point is determined depending of

  results of the analysis (step S105).

  This colorimetric process (S105) is illustrated in detail in the flowchart shown in Figures 8 to 10. In the colorimetric process, one of the photometric elements 9R, 9G and 9B which outputs the highest photometric value is determined. Then the photometric values of the other two of the photometric elements 9R, 9G and 9B are converted into relative values (step S201) assuming that the largest value is equal to 100. Then, in the following steps,

  the color of the object is determined (see figures 8 to 11).

  If the relative photometric value corresponding to the photometric element 9B (hereinafter called BLUE output signal) is equal to 100 (YES response in step S202), control proceeds to step S203 where it is estimated whether the absolute value of a difference between the BLUE output signal and the relative photometric value corresponding to the photometric element 9R (hereinafter referred to as RED output signal) is less than or equal to 10. If the absolute value of a difference between the BLUE output signal and the RED output signal is not less than or equal to (response NO to step S203), the command goes to step S204 where it is estimated if the absolute value of a difference between the BLUE output signal and the relative photometric value corresponding to the photometric element 9G (hereinafter called GREEN output signal) is less than or equal to 10. If the absolute value of a difference between the BLUE output signal and the signal so rtie GREEN is not less than or equal to 10 (response NO to step S204), the command goes to step S205 o it is estimated if the GREEN output signal is less than or equal to 60. If the output signal GREEN is less than or equal to 60 (YES response in step S205), it is estimated if the RED output signal is less than or equal to 60 (step S206). If the RED output signal is less than or equal to (YES response in step S206), it is estimated if the absolute value of a difference between the GREEN output signal and the RED output signal is less than or equal to 10 - (step S207). If the absolute value of the difference between the GREEN output signal and the RED output signal is equal to or less than 10 (YES response in step S207), it is estimated that the color is blue (step S208). In this case, the AEV correction value is set to +1.6,

  which comes from memory 21.

  In other words, the color is determined to be BLUE when: (1) the BLUE output signal is equal to 100 (which is indicated below in the form BLUE = 100);

(2) GREEN <60;

(3) RED <60;

(4) I GREEN - RED I> 10.

  If, in step S203, the absolute value of the difference between the BLUE output signal and the RED output signal is less than or equal to 10 (YES response in step S203), it is estimated in a step S221 if the GREEN output signal is less than or equal to 60. If the GREEN output signal is less than or equal to 60 (YES response in step S221), it is determined that the color is MAGENTA (step S222). In this case, the AEV correction value is

  established at -0.2, which is derived from memory 21.

  In other words, the color is determined to be MAGENTA when:

(1) BLUE = 100;

  (2) I BLUE - RED I <10 (i.e. RED> 90); and

(3) GREEN 60.

  If, in step S204, the absolute value of the difference between the BLUE output signal and the GREEN output signal is less than or equal to 10 (YES response in step S204), it is estimated in a step S211 if the signal

  RED output is less than or equal to 60.

  If the RED output signal is less than or equal to 60 (YES response in step S211), it is determined that the color is CYAN (step S212). In this case, the AEV correction value is set to -0.2, which is

derived from memory 21.

  In other words, the color is determined to be CYAN when:

(1) BLUE = 100;

  (2) I BLUE - GREEN I <10 (i.e. GREEN> 90); and

(3) RED <60.

  If the BLUE output signal is equal to 100 (YES response in step S202), but if it is not determined that the color is BLUE, CYAN or MAGENTA, control proceeds to step S501 (see Figure 11 ) o it is determined that the color is ACHROMATIC. In this case, the AEV correction value is determined to be zero (step

S502).

  If the BLUE output signal is not equal to 100 (response NO in step S202), control proceeds to a step

S302 in Figure 9.

  If the GREEN output signal is equal to 100 (YES response in step S302), the absolute value of a difference between the GREEN output signal and the BLUE output signal is not less than or equal to 10 (response NO in step S303), the absolute value of a difference between the GREEN output signal and the RED output signal is not less than or equal to 10 (answer NO in step S304), the output signal BLUE is less than or equal to 60 (YES response in step S305), the RED output signal is less than or equal to 60 (YES response in step S306) and the absolute value of the BLUE output signal and the signal RED output is less than or equal to 10 (YES response in step S307), the color is estimated to be GREEN (step S308). In this case, the AEV correction value is

  established at -0.4, which is derived from memory 21.

  In other words, the color is determined to be GREEN when;

(1) GREEN = 100;

(2) BLUE <60;

(3) RED <60; and

(4) I BLUE - RED <10.

  If the GREEN output signal is equal to 100 (YES response in step S302), the absolute value of the difference between the GREEN output signal and the BLUE output signal is less than or equal to 10 (YES response to the step S303) and the RED output signal is less than or equal to 60 (YES response in step S221), it is determined that the color is CYAN (step S322). In this case, the AEV correction value is set to -0.2, which is

derived from memory 21.

  In other words, the color is determined to be MAGENTA when:

(1) GREEN = 100;

  (2) I GREEN - BLUE I <10 (i.e. BLUE 2 90); and

(3) RED <60.

  If the GREEN output signal is equal to 100 (YES response in step S302), the absolute value of the difference between the GREEN output signal and the BLUE output signal is not less than or equal to 10 (NO response in step S303), the absolute value of the difference between the GREEN output signal and the RED output signal is less than or equal to 10 (YES response in step S304) and the BLUE output signal is less than or equal at 60 (YES response in step S311), it is determined that the color is YELLOW (step S312). In this case, the correction value

  AEV is set to -1.7, which is derived from memory 21.

  In other words, the color is determined to be YELLOW when:

(1) GREEN = 100;

  (2) I GREEN - RED 10 (i.e. RED 2 90); and

(3) BLUE <60.

  If the GREEN output signal is equal to 100 (answer YES in step S302), but if the color is not determined as being GREEN, YELLOW or CYAN, the command goes to step S501 where the color is determined as being ACHROMATIC. In this case, the correction value

  AEV is determined to be zero (step S502).

  If the GREEN output signal is not equal to 100 (response NO in step S302), the command goes to a step

S402 of figure 10.

  If the BLUE output signal is not equal to 100 (NO response in step S202), and if the GREEN output signal is not equal to 100 (NO response in step S302), the absolute value d 'a difference between the RED output signal and the BLUE output signal is not less than or equal to 10 (NO response at step S403), the absolute value of a difference between the RED output signal and the signal GREEN output signal is not less than or equal to 10 (NO response in step S404), GREEN output signal is less than or equal to 60 (YES response in step S405), BLUE output signal is less or equal to 60 (YES response in step S406) and the absolute value of the BLUE output signal and GREEN output signal is less than or equal to 10 (YES response in step S407), it is estimated that the color is RED (step S408). In this case, the AEV correction value is set to +0.6, which is derived

from memory 21.

  In other words, the color is determined to be RED, when:

(1) RED = 100;

(2) BLUE 60;

(3) GREEN 60; and

(4) I BLUE - GREEN I S 10.

  If the RED output signal is equal to 100 (NO response in step S202; NO response in step S302), the absolute value of the difference between the RED output signal and the BLUE output signal is less than or equal at 10 (YES response in step S403) and the GREEN output signal is less than or equal to 60 (YES response in step S421), it is determined that the color is MAGENTA (step S422). In this case, the AEV correction value is

  established at -0.2, which is derived from memory 21.

  In other words, the color is determined to be MAGENTA when:

(1) RED = 100;

  (2) j RED - BLUE I 10 (i.e. BLUE> 90); and

(3) GREEN 60.

  If the RED output signal is equal to 100 (response NO in step S202; response NO in step S302), the absolute value of the difference between the RED output signal and the BLUE output signal is not less than or equal to 10 (NO response in step S403), the absolute value of the difference between the RED output signal and the GREEN output signal is less than or equal to (YES response in step S404) and the signal BLUE output is less than or equal to 60 (YES response in step S411), it is determined that the color is YELLOW (step S412). In this case, the AEV correction value is set to -1.7,

  which is derived from memory 21.

  In other words, the color is determined to be YELLOW when:

(1) RED = 100;

  (2) I RED - GREEN I <10 (i.e. GREEN 2 90); and

(3) BLUE S 60.

  If the RED output signal is equal to 100 (response NO in step S202; response NO in step S302), but if the color is not determined to be RED, YELLOW or MAGENTA, control proceeds to l step S501 where the color is determined to be ACHROMATIC. In this case, the AEV correction value is determined to be

equal to zero.

  For example, if the RED, GREEN and BLUE output signals (relative values) have the values indicated in FIG. 7A, the controller 20 judges that the color of the object is yellow. If the RED, GREEN and BLUE output signals (relative values) have the values indicated in FIG. 7B, the control device 20

  believes that the color of the object is blue.

  In step S106 (Figure 6), depending on the results of the colorimetry operation, a photometric correction calculation is performed, calculation during which the exposure value EV 'obtained in step S104 and the value of AEV correction determined during the colorimetry operation (Figures 8 to 11) are added, whereby the corrected optimal exposure value EV is obtained. The AEV correction value, which is established during the colorimetry operation, is determined in advance as a function of the difference in reflection factors between several different colors, and the values are stored in advance in the memory 21. Table 1 shows a relationship between colors, reflectance values and AEV correction values. In steps S209, S213, S223, S309, S313, S323, S409, S413 and S123 in Figures 8 to 10, reference is made to the AEV correction values which are stored in memory 21 and indicated in Table 1.

TABLE 1

  color reflection factor correction values AEV

YELLOW 60% -1.7

MAGENTA 20% -0.2

CYAN 20% -0.2

BLUE 6% +1.6

GREEN 23% -0.4

RED 12% +0.6

  Then, if the trigger SWR switch is closed (i.e. if the trigger button of the camera 100 is fully pressed) (YES response in step S107), the exposure parameters (i.e. shutter speed and aperture value) are calculated based on the optimal exposure value EV obtained in step S106 and, based on exposure parameters calculated, an exposure adjustment is made by the adjustment unit 15

exposure (step S108).

  In accordance with the above process, the optimal exposure value is determined based on the color of the object corresponding to the chosen distance measurement point, and the exposure parameters are determined. Therefore, for example, if the color of an object at the point where the distance is measured is yellow, the AEV correction value is determined to be -1.7. Consequently, the optimal exposure value EV is 1.7 less than the measured exposure value EV 'and, consequently, the exposure parameters obtained, to be used for photography, have been modified so as to avoid the state of underexposure. In another example, if the color of the object at the point where distance5 is measured is blue, it is determined that the AEV correction value is +1.6. Consequently, the optimal exposure value EV is modified so as to be 1.6 greater than the measured exposure value EV 'and, consequently, the exposure parameters obtained, to be used for photography, have been changed to prevent overexposure. As before, depending on the embodiment, an imprecise state of exposure due to the difference in colors of the subject can be prevented, and a photograph can be taken.

to an optimal exposure state.

  It should be noted that the correction values are not necessarily stored in the memory 21, but that they can be assigned by the algorithm. However, by using the memory 21 and by referring to the stored values, it is easy to modify the correction values when necessary, without

modification of the algorithm.

  In the embodiment, a colorimetric operation is performed based on the output signals from the photometric elements 9R, 9B and 9G, and the AEV exposure compensation value is determined by

  depending on the color obtained, with reference to Table 1.

  However, the invention is not limited to this embodiment. For example, the AEV exposure compensation value can be calculated directly based on the output signals from the photometric elements 9R, 9B and 9G. In particular, in step S209, the AEV exposure compensation value is determined with reference to Table 1. However, in step S209, instead of referring to memory 21, the AEV exposure compensation value

  can be calculated according to formula (F1) above

  below: AEV = (BlEU - ((GREEN + RED) / 2)) * 0.025 +0.6 ... (F1) where 0.025 is a calculation coefficient and 0.6 is a correction value when the color is blue . If the calculation is carried out assuming that Blue output signal = 100, Green output signal = 60 and Red output signal = 60, the result is AEV = + 1.6, which

  corresponds to AEV indicated in table 1.

  Similarly, step S313 or S413 can be replaced by the formula (F2): AEV = (((GREEN + RED) / 2-BlEU) * 0.025 + 0.7) * (- 1) ... (F2) o 0.025 is a calculation coefficient and 0.7 is a correction value when the color is yellow. We reverse the sign by multiplying by (-1), because the exposure value is compensated in a direction in which a

  photography is taken in the state of overexposure.

  Step S309 can be replaced by the formula (F3): AEV = ((GREEN - ((RED + BlEU) / 2)) * 0.025 -0.6) * (- 1) ... (F3) o 0.025 is a calculation coefficient and -0.6 is

  a correction value when the color is green.

  If the calculation is carried out assuming that Blue output signal = 60, Green output signal = 100 and Red output signal = 60, the result is AEV = -0.4, which

  corresponds to AEV indicated in table 1.

  Each of steps S223 and S423 can be replaced by the formula (F4):

  AEV = (((RED + BLUE) / 2-GREEN) * 0.025 -0.8) * (- 1) ... (F4)

  where 0.025 is a calculation coefficient and -0.8 is

  a correction value when the color is magenta.

  Step S409 can be replaced by the formula (F5):

  AEV = (RED ((BLUE + GREEN) / 2)) * 0.025 -0.4 ... (F5)

  where 0.025 is a calculation coefficient and -0.4 is

  a correction value when the color is red.

  Steps S213 and S323 can be replaced by the formula (F6): AEV = ((((BLEU + GREEN) / 2) -ROUGE) * 0.025 -0.8) * (- 1) ... (F6) o 0.025 is a calculation coefficient and -0.8 is a correction value when the color is cyan. Since the AEV correction value can be obtained by calculation, a memory for storing AEV is not necessary. Furthermore, in this modification, the SEV exposure compensation values correspond not only to the color, but also to

  the amount of light received, can be obtained.

  It should be noted that, in the above modification, the memory 21 can be used for the storage of coefficients and correction values for the formulas F1 - F6. If these values are stored in the memory 21, when it becomes necessary to modify the coefficients and / or correction values, they can be modified relatively easily simply by a new storage of the values, without modification of

the algorithm.

  The invention can also be modified from

various ways.

  If the invention is to be applied to a camera provided with a single distance measuring point, the photometric point and the color point can be defined so as to coincide with the

distance measurement.

  The color points do not have to coincide with the distance measurement points. In particular, in a camera in which the photometric zones are wider than the zones defined for the distance measurement, it is advantageous that the colorimetry operation is carried out

  vis-à-vis the photometric zones.

  In the embodiment and modification described above, the AEV correction value is determined on the basis of photometry at a distance measurement point; however, the invention can be applied to a camera without a unit

distance measurement.

  Furthermore, the invention is not limited to a single-lens reflex camera or to a camera using a photosensitive film, but it can be applied to a camera.

digital shooting.

  As described above, given that the camera according to the invention is equipped with a colorimeter to detect the color of an object and that it performs exposure adjustment by correcting the measured exposure value by a photometer as a function of the color measured by the colorimeter, one eliminates a state of overexposure or underexposure due to differences between the light reflection factors on the basis of differences in color of the object, thanks whereby it becomes possible to obtain optimal exposure parameters. In particular, in the invention, photometry and colorimetry are carried out at a distance measurement point at which the distance of an object is measured. Thus, part of an object on which a development is carried out is photographed in the state of exposure

optimal.

  It goes without saying that many modifications can be made to the camera and to the exposure adjustment device described and represented.

  without departing from the scope of the invention.

Claims (6)

  1. Camera, characterized in that it comprises a photometry device (13) which is used to detect the brightness of an object, a colorimetry device (12) which detects a color of this object, and a control device (20) which determines an exposure value as a function of an output signal from the photometry device, the control device compensates for this exposure value according to the color of the object detected by the device of colorimetry. 2. Camera according to claim 1, characterized in that the control device comprises a storage device (21) which stores several compensation values corresponding to several colors, the control device compensating the exposure value by adding a compensation value, stored in the storage device,   corresponding to the color of the object.   3. Camera according to claim 1, characterized in that it further comprises a device (8) for distance measurement which detects a distance of said object at a predetermined point in a photography frame, the photometry device detecting the brightness of the object in an area, inside the photography frame, which includes the predetermined point, and the colorimetric device detecting the color of the object in an area, inside the photography frame , who includes the predetermined point.   4. Camera according to claim 1, characterized in that it further comprises a distance measuring device (8) capable of detecting a distance of said object at several distance measuring points defined inside of a photography frame of the camera, the photometry device capable of detecting the brightness of the object in any area, inside the photography frame, which respectively contains this plurality of measurement points of distance, and the colorimetry device capable of detecting the color of the object in any zone, inside the photographic frame, which respectively comprises this plurality of distance measurement points, the distance of said object being detected relative to a point chosen from the plurality of distance measurement points, the exposure value being detected in an area corresponding to the point chosen from the distance measurement points this, and the color of the object being detected in an area corresponding to the point chosen from the measurement points of distance.   5. Camera according to claim 1, characterized in that the colorimetry device comprises several photometric elements (9D, 9R, 9G, 9B) intended to measure an amount of received light having different wavelength ranges , and a determination system which determines the color on the basis of the light quantity values detected by the photometric elements.   6. Exposure adjustment system for a camera, characterized in that it comprises a photometry device (13) which is used to detect the brightness of an object, a colorimetry device (12) which detects a color of the object, and a controller (20) which determines an exposure value based on an output signal from the photometry device, the controller compensates for the exposure value based on the color   of the object detected by the colorimetry device.