Photographic camera with arrangement for determining scene light sufficiency and for controlling exposure timing

Claim 2

In a photographic camera, an arrangement comprising, in combination, first circuit means for determining scene light sufficiency; second circuit means for controlling exposure timing; a photoelectric component; electronic switch means operative in a first state thereof for operatively connecting said photoelectric component to said first circuit means for determining scene light sufficiency, and operative in a second state thereof for operatively connecting said photoelectric component to said second circuit means for performing an exposure timing operation; and mechanical switch means connected to said electronic switch means and operative for causing the latter to assume either said first or said second state thereof.

Claim 3

An arrangement as defined in claim 1, wherein said first circuit means comprises signalling means, first threshold-detecting means having an output connected to said signalling means and having a respective first input, a voltage source, a resistor having one terminal connected to one terminal of said source and having its other terminal connected to said first input, and wherein said second circuit means comprises a shutter-control electromagnet, second threshold-detecting means having an output connected to said electromagnet and having a respective second input, and a timing capacitor connected to said second input for applying thereto a voltage varying in dependence upon the voltage across said timing capacitor, and wherein said photoelectric component has one terminal connected to the other terminal of said voltage source, and wherein said electronic switch means is operative in said first state for operatively connecting the other terminal of said component to said first input to form a voltage divider comprised of said resistor and said photoelectric component and having a tap connected to said first input, and wherein said electronic switch means comprises a first electronic switch connected in parallel with said timing capacitor to become conductive when said electronic switch means is in said first state for short-circuiting said timing capacitor, and a second electronic switch conductive when said electronic switch means is in said second state and operative for establishing a flow of common current through said timing capacitor and said photoelectric component to effect a change of the voltage across said capacitor at a rate dependent upon scene light, and wherein said mechanical switch means comprises a single mechanical switch operable for causing said electronic switch means to assume either said first or said second state thereof.

Claim 4

An arrangement as defined in claim 2, wherein said first and second electronic switches are connected in series, and wherein said second electronic switch is connected in parallel with said resistor, and wherein said electronic switch meaNs further includes inverter means connected to one of said electronic switches and operative for causing one of said electronic switches to be non-conductive when the other of said electronic switches is conductive.

Claim 5

An arrangement as defined in claim 2, wherein said first and second electronic switches are connected in series, and wherein said second electronic switch is connected between said photoelectric component and said timing capacitor in series therewith, and wherein said electronic switch means further includes inverter means connected to one of said electronic switches and operative for causing one of said electronic switches to be non-conductive when the other of said electronic switches is conductive, and a third electronic switch connected between said first input and said other terminal of said photoelectric component and so connected as to be conductive when said electronic switch means is in said first state.

Claim 6

An arrangement as defined in claim 4, wherein said second electronic switch comprises two transistors connected to each other in Darlington configuration.

Claim 7

An arrangement as defined in claim 2, wherein said first and second electronic switches have control electrodes for controlling the conductivity of the respective switches, and wherein said electronic switch means comprises a voltage divider having a tap connected to the control electrode of at least one of said switches, and wherein said single mechanical switch is operative for connecting said voltage divider of said electronic switch means across said voltage source to render said one of said switches conductive.

Claim 8

An arrangement as defined in claim 2, the camera including a movable shutter-release member activatable by the camera user, said shutter-release member being arranged to contact and activate said single mechanical switch.

Claim 9

An arrangement as defined in claim 2, the camera including a movable shutter-release member and a further member coupled to said shutter-release member and movable in response to movement of the latter, said further member being arranged to contact and activate said single mechanical switch.

Claim 10

An arrangement as defined in claim 2, and further including a release switch for connecting said voltage source to said first and second circuit means, and wherein said single mechanical switch is a two-position switch operative in one of its positions for connecting said voltage source to said electronic switch means via said release switch and operative in the other of its positions for short-circuiting said release switch.

Claim 11

An arrangement as defined in claim 2, wherein said electronic switch means further comprises means operative when said electronic switch means is in said first state thereof for energizing said electromagnet by connecting said electromagnet directly across said voltage source.