| 摘要 |
An electrical system for automatically determining exposure time in a single-lens reflex camera. An electrical circuit includes a storage capacitor and a logarithmic compression element. Through the latter the storage capacitor is charged sequentially to provide a pair of voltages, and the electrical circuit utilizes the difference between these voltages for controlling the exposure time. One of these voltages is determined at least in accordance with the light intensity coming from the object to be photographed and the other of these voltages is determined at least in accordance with the film speed. Thus, the signals according to light intensity and film speed are logarithmically compressed prior to charging of the storage capacitor by way of the logarithmic compression element. In addition, one of the latter signals is modified in accordance with the selected diaphragm setting, so that the modified signal is logarithmically compressed prior to charging of the capacitor. |
