| 摘要 |
PURPOSE:To cover a wide photometry range without overflowing while using a small-scale counting means by varying counting conditions corresponding to variation in photoelectric conversion output with the quantity of incident light. CONSTITUTION:An IC 100 for photometry obtains the photoelectric conversion output corresponding to the quantity of incident light. In this case, a stop is fully opened. The counter in the photometry block 210 in a gate array 200 performs counting operation corresponding to the output and a computer 300 calculates the quantity of incident light from the counted value. A shutter speed and a stop value corresponding to the photometry value are also calculated. Those are transferred to a computer 400 for system control and then the computer 400 generates a signal for specific displaying operation regarding a shutter speed or stop value corresponding to the current quantity of incident light to perform preliminary measurement. A computer 300 for photometry monitors the counted value of the gate array 200 and resets the counting conditions repeatedly so that the counter does not overflow. Consequently, a counting means consisting of a relatively small number of stages can handle a dynamic range of wide-range photometry because of open-aperture photometry.
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