| 摘要 |
PURPOSE:To effectively remove the noises of a photometer by sampling signals from photoelectrically converting means at time intervals each corresponding to the intermediate value of at least two different periods of changes in the quantity of light being measured and averaging sampled values. CONSTITUTION:Light being measured is converted to electric signals by a photodetector element 1 and logarithmically compressed by a logarithmic amplifier 2. Further, the signals are removed with their high frequency components by an LPF3 and inputted to an A/D converter (ADC)4. The time constant of the LPF3 is set larger than the analog-to-digital converting time of the ADC4 so that it holds the signals for a time required for the ADC4 to conduct one analog- to-digital conversion. A CPU5 controls the operation of the ADC4. That is, the CPU5 calculates a stop value for a proper exposure, an exposure time value and the like by using the digital signals which are the output of the ADC4 and signals from other switches, interfaces and the like, displays the calculated stop value and the exposure time value and, based on the calculated values, controls an exposure sequence. Thus, the noises of a photometer can be effectively removed.
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