Electric exposure meter

Abstract

An electric exposure meter for storing the brightness of a photographic object as an electric voltage of a magnitude corresponding thereto in order to control the exposure time by using the voltage thus stored.

We claim: 
     
       1. An exposure measuring system comprising a gang switch including first and second movable contacts mechanically and electrically connected with each other, and two groups of corresponding fixed contacts arranged so that when the first movable contact is engaged with any one of the first group of fixed contacts the second movable contact is engaged with the corresponding fixed contact; a photoconductive element and a load resistance connected in series, said photoconductive element being connected to said first movable contact while said load resistance is connected to said second movable contact;   two groups of resistances each comprised of a plurality of equal value resistors connected in series, another resistance connected between said two groups of resistances, one end of said series connected resistances being connected to a DC electric source, each of said fixed contacts being connected to one end of an associated resistor so that in any contact position of said gang switch the voltage across the opposite ends of said series connection of the photoconductive element and load resistance is the same; and   measuring means connected between the photoconductive element and the load resistance for measuring the voltage across the load resistance;   whereby the output voltage is in linear relation relative to the brightness value of the object as sensed by the photoconductive member.   
     
     
       2. An exposure measuring system according to claim 1 wherein said measuring means comprises a storing means for storing said output voltage for controlling the operation of a shutter of a camera. 
     
     
       3. An exposure measuring system according to claim 2 wherein said measuring means comprises an indicator means for indicating said voltage stored in said storing means. 
     
     
       4. An exposure system according to claim 3 wherein said indicator is a voltmeter. 
     
     
       5. An exposure measuring system according to claim 2 wherein said storing means is a capacitor. 
     
     
       6. An exposure measuring system according to claim 1 wherein said photoconductive element is made of cadmium sulfide. 
     
     
       7. An exposure measuring system according to claim 1 wherein said photoconductive element is a compound photoconductive member. .Iadd. 8. An exposure measuring system comprising: means including a voltage divider having a series connected network of a resistor and a photoconductive means, said photoconductive means being exposed to light, for producing a potential at the junction point of said resistor and photoconductive means, said potential varying relative to a predetermined point in a linear relation to the BV value of the brightness of the light incident on said photoconductive means;   means including a variable resistor device having a resistor portion connected in parallel with said series connected network and adjustable in accordance with a light unrelated photographing parameter in a manner to vary the potentials at both end terminals of said voltage divider equally and in the same direction and vary said potential at the said junction point with changes in said last mentioned potential for each increment of adjustment of said parameter corresponding to changes of potential effected by unit changes in the brightness of said incident light; and storage means connectable with said means for producing a potential for storing said potential in said storage means. .Iaddend. .Iadd. 9. The system of claim 8 wherein said photoconductive means includes a pair of photoconductive elements coupled as a compound photoconductive cell.