Autoranging method and system for testing the speeds of a camera shutter

A method for measuring shutter speed in a camera comprising:

• a. positioning the camera adjacent to a light source;
• b. activating the camera shutter so that a pulse of light passes therethrough;
• c. sensing the intensity and duration of the light pulse;
• d. generating a train of clock pulses for which the instantaneous frequency is proportional to the intensity of the light pulse;
• e. counting said clock pulses;
• and
• f. displaying the shutter speed as a function of the counted pulses.

A method for measuring the shutter speed in a camera comprising:

• a. positioning the camera adjacent to a light source;
• b. activating the camera shutter so that a pulse of light passes therethrough;
• c. sensing the intensity and duration of a light pulse at a point in the focal plane of the camera;
• d. generating a train of clock pulses for which the instantaneous frequency thereof is proportional to the instantaneous intensity of the light pulse;
• e. counting the train of clock pulses;
• f. automatically displaying a standard shutter speed which most accurately represents the effective speed of the tested shutter;
• and
• g. displaying an error ratio relating the measured effective shutter speed to the standard shutter speed display.

A system for testing the shutter of a camera comprising:

• a. a photodetector positioned at the focal plane of the camera;
• b. a variable threshold voltage comparator connected to the photodetector;
• c. a first oscillator;
• d. means for generating an initialization pulse fed by the variable threshold voltage comparator and the first oscillator;
• e. a countdown shift register fed by the initialization pulse generating means;
• f. a voltage controlled oscillator fed by the photodetector;
• g. means for dividing the frequency of the voltage controlled oscillator by a variable divisor, the variable divisor being generated from the output of the countdown shift register;
• h. a range shift register activated by the initialization pulse generating means;
• i. logic means for reloading the countdown shift register fed by the range shift register;
• j. a ratio counter fed by the frequency dividing means and activated by the initialization pulse generating means;
• k. logic means for reloading the ratio counter fed by the range shift register;
• l. means for generating a range change pulse to activate the range shift register, the range change pulse generating means being fed by the ratio counter and the range shift register;
• and
• m. a ratio display fed by the ratio counter and latched by the variable threshold voltage comparator.