Range synchronized flash photographic apparatus and method for achieving optimum flash exposure
First Claim
1. Apparatus for photographing a subject, comprising:
- a scanning shutter which when actuated produces a predetermined, timewise variation in exposure aperture area;
ranging means for providing an output representative of the range of a subject;
a flash unit; and
means for actuating the shutter to start its scanning, the improvement comprising;
means for firing the flash unit to produce a flash of illumination after a time period, measured from the first light through the shutter, dependent on the output of the ranging means, the relationship between the time period and subject range establishing a parametric relationship between the brightness of the subject due to its flash illumination and the scanning time of the shutter, the inverse of this parametric relationship constituting the timewise variation in the exposure aperture area of the shutter.
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Accused Products
Abstract
An image recording apparatus and method employing a diaphragm shutter having a time variable exposure aperture with flash firing, following actuation of the shutter, after a time interval dependent on subject range. The functional relationship between the time interval and subject range establishes a parametric relationship between the brightness of the subject due to its flash illumination and the scan time of the diaphragm shutter. The inverse of this parametric relationship constitutes the timewise variation in the exposure aperture area of the shutter. Consequently, whenever the subject is within a predetermined maximum distance from the camera, dependent upon the maximum aperture area attainable by the shutter, the instantaneous product of subject brightness and aperture area will be a constant with the result that proper exposure of the photographic film is achieved independent of the subject range.
49 Citations
24 Claims
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1. Apparatus for photographing a subject, comprising:
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a scanning shutter which when actuated produces a predetermined, timewise variation in exposure aperture area; ranging means for providing an output representative of the range of a subject; a flash unit; and means for actuating the shutter to start its scanning, the improvement comprising; means for firing the flash unit to produce a flash of illumination after a time period, measured from the first light through the shutter, dependent on the output of the ranging means, the relationship between the time period and subject range establishing a parametric relationship between the brightness of the subject due to its flash illumination and the scanning time of the shutter, the inverse of this parametric relationship constituting the timewise variation in the exposure aperture area of the shutter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for recording the image of a subject illuminated at least in part by actuation of a flash unit to produce a pulse of transient illumination and employing a scanning shutter arrangement actuatable to initiate an exposure interval during which said shutter arrangement at least initially provides progressively increasing aperture values through which scene light from said subject is transmitted to a photosensitive recording medium, said method comprising the steps of:
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determining the distance between said subject and said flash unit and defining a time interval related to said distance; driving said shutter arrangement at a scanning rate selected in accordance with said relationship between subject distance and time; and actuating said flash unit to produce said pulse of illumination following said actuation of said shutter after a time period related to said time interval so that said pulse is automatically synchronized with a narrow range of aperture values selected in accordance with subject distance. - View Dependent Claims (10, 11, 12)
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- 13. In a flash exposure control system for recording scene images of a subject to produce a proper exposure of a photosensitive recording medium independent of subject distance, said system having a scanning shutter arrangement actuatable for at least initially providing increasing aperture values during an exposure interval within which scene light is transmitted to the photosensitive recording medium, said shutter arrangement providing said increasing aperture values at a predetermined scanning rate such that following actuation of said shutter arrangement, progressively increasing aperture values are provided at progressively increasing time intervals following said actuation, means for producing a flash of illumination during said exposure interval to illuminate said subject with transient illumination, means for determining the distance of said subject from said flash producing means and for synchronizing the production of said flash with operation of said scanning shutter arrangement so that transient illumination reflected from said subject is transmitted through said shutter arrangement to said recording medium by a narrow range of aperture values selected in accordance with subject distance, the improvement wherein said distance determining and flash synchronizing means comprises means for defining a range related time interval corresponding to subject distance and for producing said flash of illumination responsive to a lapse of a time period measured from first light of said shutter arrangement and proportional to said range related time interval to thereby produce said flash over a narrow range of aperture values automatically selected in accordance with subject distance.
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24. A method for recording the image of a subject illuminated at least in part by actuation of a flash unit to produce a pulse of transient illumination and employing a scanning shutter arrangement actuatable to initiate an exposure interval during which said shutter arrangement at least initially provides progressively increasing aperture values through which scene light from said subject is transmitted to a photosensitive recording medium, said method comprising the steps of:
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transmitting a burst of energy toward said subject and receiving an echo therefrom so as to define a time interval related to subject distance; driving said shutter arrangement at a scanning rate selected in accordance with the relationship between subject distance and time; and actuating said flash unit upon receipt of said echo to produce said pulse of illumination, following said actuation of said shutter, after a time period related to said time interval so that said pulse is automatically synchronized with a narrow range of aperture values selected in accordance with subject distance.
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Specification