| 摘要 |
<p>A flashtube (18) is quenched when a light-responsive integrating circuit (15) has received a requi red amount of light. The amount is reduced if the ambient light exceeds a certain level. A light-level sensing circuit (14) measures the intensity of the ambient light. A threshold-setting circuit (22,32,34), responsive to the sensing circuit (14) causes the amount of light needed to be sensed by the integrating circuit (15). The circuit is used for the terminating the flash in bright ambient light to be less than the amount of light required to be sensed for terminating the flash in low ambient light. Alternatively, the integrating circuit has two capacitors, one of which is switched out when ambient light is bright. A single element may be used to sense both the ambient light and the flash light.</p> |
