| 摘要 |
PURPOSE:To prevent the unnecessary power consumption of a power source battery by deciding that a subject can not be tracked and generating a warning when the ratio of the lst driving quantity and current driving quantity of a photographic lens is larger than a specific value. CONSTITUTION:When a distance ring rotates, an ADR switch generates pulses corresponding to the angle of the rotation and an ADR counter 190 counts them and inputs the counted value to a CPU 61. Then the ratio of the last driving quantity ADR1 and current expected driving quantity ADR2 of the photographic lens is compared with the specific value. When the ratio is larger than the specific value, it is decided that the moving speed of the subject is too fast to track and the 1st LED 154 of a warning display circuit 67 is made to illuminate, thereby warning the failure in focusing operation. A waste of the power source battery is eliminated for a subject for which the focusing operation need not be carried on. |
