Photographic exposure apparatus for providing small apertures

In a photographic exposure control system for defining an aperture value in operative relation to a given optical path, a blade mechanism comprising a pair of blade members having a given blade axis, each of said blade members having an open portion therein with at least a main section thereof lying on the blade axis, the main section of each open portion exceeding at some point a given width as measured transverse to the blade axis, means for mounting said blade members for displacement across said given optical path along a blade path in which said blade axes are maintained in a substantially parallel relation to provide at least partial coincidence of said open portions at said given optical path thereby defining an operative aperture value thereat in accordance with the extent of said coincidence, the improvement comprising:

• the open section of one of said blade members having a relatively narrow, elongated first slit extending in leading relation, as viewed with respect to blade displacement, from the main section thereof;
• and
• the open portion of the other of said blade members being formed by a pair of openings comprising a relatively narrow, elongated second slit spaced in leading relation from another opening which defines the main section of the open portion and at an angle to the axis of its blade member such that during initial displacement of said blade members, the leading end of said first slit passes across said second slit and then out of coincidence therewith at said optical path to define, in accordance with the intersecting portions of said slits, a relatively small initial aperture value as compared to the relatively large aperture value when the main sections of each open portion are brought into increasing coincidence.

A photographic exposure control system for exposing, under ambient or flash illumination, photographic material located at a given film plane, said system comprising a housing having an opening therein, a lens system for directing image-carrying rays along a given exposure path from a scene through said housing opening and for focusing such rays on such photographic material, means for sensing the brightness of said scene, means for unblocking and blocking said exposure path and said sensing means, means for actuating said unblocking and blocking means to unblock said exposure path and thereby initiate an exposure cycle, means responsive to said sensing means for actuating said unblocking and blocking means to block said path following the unblocking thereof so as to terminate said cycle, said unblocking and blocking means including a pair of blade members mounted for displacement with respect to each other in overlying relation along the same blade path, each of said blade members having a primary and a secondary open portion which when displaced into at least partial coincidence with the corresponding open portion of the other blade member respectively define a primary aperture value over said exposure path and a secondary aperture value over said brightness sensing means, each of said secondary open portions having a main section exceeding at some point a given width as measured transverse to said blade path and an elongated slit of narrow width as compared to said given width, the elongated slit of each blade member being located in leading relation, as viewed with respect to blade displacement, to the main section of its respective open portion, at least one of said slits extending at an angle to said blade path and to the other slit so that during initial displacement, the leading end of at least one of said slits passes across the other slit and then out of coincidence therewith over said sensing means to define, in accordance with the intersecting portions of said slits, a relatively small initial aperture value thereat as compared to the relatively large aperture value when the main sections of each open portion are brought into increasing coincidence.