Motion-picture camera programmed for fadeover effects

Abstract

The light-sensitive negative-feedback diaphragm control system of the motion-picture camera includes a stepper-motor coupled to the diaphragm, and a control circuit generating stepper-motor drive pulses. The control circuit includes an oscillator having a time-constant circuit which establishes the repetition frequency of the drive pulses. m different repetition frequencies can be established for the drive pulses, using m semiconductor switches each connected to the time-constant circuit. A program-step counter counts program-step-change signals generated during film transport, and a '1' signal appears on successive ones of the counter outputs. The outputs include, in succession, a fade-out output group, a rewind output group, and a fade-in output group. Each such output group contains m outputs. Logic circuitry connected to the outputs of the program-step counter imbalances the diaphragm control system and controls the film transport motor, to effect fade-out, then rewind, then fade-in in dependence upon the program-step count. The first through mth semiconductor switches are each connected to the first through mth outputs of the fade-out output group, respectively, and to the mth through first outputs of the fade-in output group, respectively. Accordingly, during fade-out, the repetition frequency of the drive pulses is progressively increased, and during fade-in decreased.