| 摘要 |
PURPOSE:To control the switching of a driving direction by a simple calculation for an ordinary photographic lens group where the maximum photographing- enabled magnification of lenses are nearly same by switching the driving direction of the lens with a point where photographing magnification in the driving range of the lens is constant as a boundary. CONSTITUTION:A lens driving means 2 has a function for driving a part of the photographic lens 1(focusing lens 1a) during exposure, and a special photographic effect such as a soft focusing effect is obtained by driving the lens during exposure. In the case of driving the lens during exposure, the driving direction is controlled to be switched with the point where the photographing magnification in the driving range of the lens is constant as a boundary in order to evade the lens 1a's reaching a terminal and stopping during exposure. The photographing magnification beta of a main object is outputted from a photographing magnification output means 3 and compared with a specified value(for example, 1/12) by a comparison means 4. According to the compared result, the driving direction is decided by a driving direction deciding means. |
