| 摘要 |
PURPOSE:To limit the lower limit value of the aperture opening in accordance with the zoom magnification ratio of zoom lens, by selecting either one of the outputs of the pickup element and the zoom magnification ratio detecting means via the voltage limiting circuit and then supplying the selected output to the automatic aperture control device. CONSTITUTION:The output voltage of voltage limiting circuit 15 is limited by output VZ of variable resistor 14 even in case output voltage V1 of preamplifier 4 increases so much so that the F value of aperture 2 is lowered less than characteristic curve B. Automatic aperture control device 10 prevents the F value of aperture 2 from lowering less than curve B. As a result, lower limit RO is secured for the depth of field, and thus a highly infocus shooting is possible although the zoom magnification ratio increases. |
