Gain switching amplifier

Claim 2

A film reciprocity correction circuit for a shutter timing mechanism in a camera comprising: (a) a first differential amplifier; (b) a first feedback circuit operatively connected to the negative terminal of said differential amplifier to control the shutter over a first range without reciprocity correction; and (c) a second differential amplifier having a second feedback circuit operative as a continuous voltage reference and connected to the feedback circuit of said first differential amplifier for sensing the input signal magnitude of said first amplifier and for comparing said signal to said voltage reference, operative to continuously increase the gain of said first differential amplifier outside said first range to compensate for reciprocity failure of the film.

Claim 3

A camera having a shutter for controlling the time light from an image to be recorded impinges a light sensitive recording material comprising: (a) means for translating at least a portion the light from the image into an electronic signal; (b) a logarithmic compression amplifier for amplifying said electronic signal as a logarithmic function of the magnitude of said signal; (c) a second amplifier having an input to which said signal is applied, and having a predetermined gain within a predetermined range of said signal to produce an amplified signal; (d) a circuit for compensating for reciprocity failure of the recording material, including means responsive to the magnitude of said signal for controlling the gain of said second amplifier outside said predetermined range; (e) means to which said amplified signal is applied for logarithmically decompressing said amplified signal to produce a decompresses signal; and (f) means for controlling the timing of said shutter in accordance with said decompressed signal.

Claim 4

A camera having a shutter for controlling the time light from an image to be recorded impinges a light sensitive recording material comprising: (a) means for translating at least a portion the light from the image into an electronic signal; (b) a logarithmic compression amplifier for amplifying said electronic signal as a logarithmic function of the magnitude of said signal; (c) a second amplifier having an input to which said signal is applied, and having a predetermined gain within a predetermined range of said signal to produce an amplified signal; (d) a circuit for compensating for reciprocity failure of the recording material, including means responsive to the magnitude of said signal for controlling the gain of said second amplifier outside said predetermined range; (e) means to which said amplified signal is applied for logarithmically decompressing said amplified signal to produce a decompresses signal; and (f) means for controlling the timing of said shutter in accordance with said decompressed signal.

Claim 5

A camera as set forth in claim 2 wherein said circuit for compensating for reciprocity failure comprises means for control of temperature induced variation in amplification characteristics.

Claim 6

The camera of claim 2 wherein said means for controlling the gain of said second amplifier comprises: (a) a reference voltage; and (b) a third amplifier having an input connected said reference voltage and an output connected to control said second amplifier by supplying current to said second amplifier to control the gain of said second amplifier when said predetermined range of said signal is exceeded.