Photography – With exposure objective focusing means – focusing aid – or... – Plural focusing or rangefinding areas
Reexamination Certificate
1999-08-12
2001-01-16
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Plural focusing or rangefinding areas
C396S225000, C396S234000
Reexamination Certificate
active
06175693
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a camera provided with a photometry device.
Recently, cameras are provided with photometry devices for automatic exposure control. In particular, as a photometry device provided in a camera, a reflection type photometry device is widely used. The reflection type photometry device is constructed to receive light reflected by an object through an observation optical system of a camera, and measure an amount of light using a photo-sensitive element to detect brightness of the object. Based on thus detected brightness of the object, an exposure value (commonly known as an Ev value) is determined, and then, in accordance with a predetermined algorithm, exposure parameters (i.e., a shutter speed and an aperture value) are determined. This type of photometry device, however, does not detect reflectance of an object, and therefore, the exposure value, and thus, the exposure control parameters are calculated on assumption that the light reflectance is a predetermined fixed value, for example, 18%.
Therefore, when an object is a whitish subject whose light reflectance is greater than 18%, the brightness is detected to be higher than its actual brightness, and accordingly, such an object tends to be photographed in underexposed condition. When an object is a dark object whose light reflectance is lower than 18%, the brightness thereof is detected to be lower than the actual brightness, and accordingly, such an object tends to be photographed in an overexposed condition.
In order to avoid the above defects, a camera provided with an exposure correcting unit has been known. In such a camera, a photographer can modify the exposure value so that photographing is performed in a slightly overexposed condition when a whitish object is to be photographed, and for a dark object, the photographer can modify the exposure value so that photographing is performed in a slightly underexposed condition. By performing such an exposure operation with modifying the exposure value, the above-mentioned problems can be suppressed.
However, differences in the light reflectance of the object also occurs due to differences in the color of the object. For example, a yellow object, whose light reflectance is relatively high, tends to be photographed in a slightly underexposed condition, and a blue object, whose light reflectance is relatively low, tends to be photographed in a slightly overexposed condition.
Accordingly, in order to execute exposure correction taking differences in the color of the object into account, the photographer is required to recognize a relationship between the color and light reflectance of the object to optimize the exposure value using the exposure correction unit. However, it is practically impossible to require photographers to perform such exposure correction. Further, if such a correction operation is required, cameras become unsuitable for automatic photographing.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide camera provided with an improved exposure correction unit which automatically corrects exposure parameters to enable photographing at an optimum exposure condition regardless of differences in the color of objects.
For the above object, according to the invention, there is provided a camera, which is provided with: a photometry device that is used to detect brightness of an object; a colorimetry device that detects a color of the object; and a controller that determines an exposure value in accordance with output of the photometry device, the controller compensating the exposure value in accordance with the color of the object detected by the colorimetry device.
Since the exposure value is compensated in accordance with the photometry result and colorimetry results, an optimized exposure value can be obtained.
Optionally, the controller includes a storing device that stores a plurality of compensation values corresponding to a plurality of colors, and the controller compensates the exposure value by adding a compensation value corresponding to the color of the object stored in the storing device.
The compensation values are stored in the memory, and are referred to after the color has been determined. Correction of the compensation values can be dealt with relatively easily, and the algorithm for determining the correction value needs not be modified.
Optionally, the camera may further include a distance measuring device which detects a distance to the object at a predetermined point within a photographing frame, the photometry device detects the brightness of the object at an area, within the photographing frame, which includes the predetermined point, and the colorimetry device detects the color of the object at an area, within the photograhing frame, which includes the predetermined point.
Since the distance measuring point, a target point with respect to which the photometry and colorimetry operations are performed correspond to each other, the exposure value can be optimized in accordance with the photographer's intent.
Alternatively, the camera may include a distance measuring device capable of detecting a distance to the object at a plurality of distance measuring points defined within a photographing frame of the camera. In this case, the photometry device may be capable of detecting the brightness of the object at any one of areas, within the photographing frame, which respectively include the plurality of distance measuring points, and the colorimetry device may be capable of detecting the color of the object at any one of areas, within the photograhing frame, which respectively include the plurality of distance measuring points. The distance to the object may be detected with respect to selected one of the plurality of distance measuring points, the exposure value being detected at an area corresponding to the selected one of the plurality of distance measuring points, and the color of the object being detected at an area corresponding to the selected one of the plurality of distance measuring points.
Still optionally, the colorimetry device may include: a plurality of photometric elements for measuring amount of received light having different wavelength ranges; and a color determining system that determines the color based on the light amount values detected by the plurality of photometric elements.
According to another aspect of the invention, there is provided an exposure control system for a camera, which is provided with: a photometry device that is used to detect brightness of an object; a colorimetry device that detects a color of the object; and a controller that determines an exposure value in accordance with output of the photometry device, the controller compensating the exposure value in accordance with the color of the object detected by the colorimetry device.
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Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Perkey W. B.
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