1. Field of the Invention
The present invention relates to photometric devices that receive a luminous flux from a subject field and particularly to photometric devices for use with cameras.
2. Description of Related Art
It has been proposed to equip cameras with screen photometry to perform photometry by transmitting luminous flux from the subject field through a screen. Sometimes a light emitting indicating device that indicates light emitting photographic information is placed in the vicinity of the screen.
When a light emitting indicating device is provided in the vicinity of the screen, when performing screen photometry, a significant amount of light emitted from the light emitting indicating device mixes with the luminous flux from the subject field. Because of this, the photometric value output from the photometry device includes the output due to light originally emitted from the light emitting indicating device. The relative effect of this light emitting indicating device related output increases as the subject field gets darker.
For this reason, adjustment of the photometric value is performed to eliminate the luminance effect of the light emitted from the light emitting indicating device. The photometry device is divided into several areas and the luminance effect due to the light emitting indicating device is different for each of the photometric areas.
Heretofore, with photometry devices, as indicated in FIG. 4, the light receiving plane was divided into six areas. A light emitting indicating device 4', for example, a liquid crystal indicator that includes a back light illumination component 5', was placed at the bottom portion of the photometry device. A light sensor with photometry areas divided into 6 sections was used. With the center section 11a' designated ch 1, the left top periphery section 11b' designated ch 2, the right top periphery section 11c' designated ch 3, the left bottom periphery section 11d' designated ch 4, the right bottom periphery section 11e' designated ch 5, and the spot section 11f' designated ch 6, the bottom portions of the areas for ch 4 and ch 5 receive the greatest effect of the light emitted from the light emitting indicating device. Therefore, the calculation for the adjusted photometric value is performed for the upper portions by formula (1) and for the bottom portions by formula (2) that follow. EQU ch 1-3, 6 BVn=BVn/4+(11/12) (1) EQU ch 4, 5 BVn=BVn/2+(11/6) (2)
where BVn is the photometric value.
However, using the above mentioned method of adjustment, because the change is large when adjustment is made, the accuracy of the adjustment of the photometric value in relation to the actual subject field luminance value becomes only approximate so that there is a problem of poor accuracy of the photometric device when performing screen photometry.
USPTO Backgrounds
USPTO Backgrounds