| 摘要 |
In order to realize a lens barrel or camera which is light in weight and small in size and which has performance as high as a single-focus lens, a photographing optical system employed in the lens barrel or camera has four lens groups, and at least two diaphragms are arranged at different positions. Despite the simple structure it has, the photographing optical system enables switching among a number of focal lengths. The diaphragms include: a first diaphragm (diaphragm unit A) arranged at a first inter-lens position defined inside the photographing optical system and controlling the amount of light passing through the system; and a second diaphragm (diaphragm unit B) arranged at a second inter-lens position defined inside the system and controlling the amount of light passing through the system.
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