To provide a rotation locking mechanism for an effective portion allowing sure locking of the rotating angle of the effective portion and fine setting of the stages of the selective rotating angle and a framing cutter mechanism preventive of projecting image fading on a framing, simple to construct and easy to manufacture and assemble.

Right and left locking pieces 61 of a locking member 60 engage with two locking recessed portions 21 of a rotating ring 20 to keep the rotating angle of the effective portion c in a locked condition. In a movable frame 30, two cutter blades 41a, 41b opposed to each other vertically and two cutter blades 41c, 41d opposed to each other crosswise are arranged in the same plane and the cutter blades 41a-41d are kept in a slidably contacting condition by a circular plate spring 50, therefore producing reduced clearances between each of the cutter blades 41a-41d and an effect pattern 5 on an optical axis L.