A sector drive apparatus for use in an optical apparatus, the sector drive apparatus includes a sector having a first engagement opening engaged with an operation member that reciprocates in a given range and a second engagement opening engaged with a spindle fixed to a shutter substrate, the sector opening and closing a shutter opening formed in the shutter substrate in accordance with a movement of the operation member. The operation member has an engagement pin that is engaged in the first engagement opening, the first engagement opening is substantially circular that permits the operation member to rotate, and the second engagement member is an elongate opening, and swings the sector centering around the spindle to move to a position where the shutter opening is opened and closed, when the first engagement opening moves in accordance with the movement of the operation member.

 
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> Optical density-changing element, optical element and photographic unit

~ 00345