Variable focus large aperture five group camera objective - has second and third groups movable for zooming and second for close-up work

摘要

The variable-focus large-aperture camera objective with close-up setting consists of five lens groups (G1-5). The positive front group (G1) serves for object distance setting but is otherwise fixed relative to the image plane and consists of a bi- convex doublet (L1,2) and a single positive meniscus lens (L3). The negative second group (G2), consisting of a single meniscus (L4) and a bi-concave doublet (L5,6), and the positive third group (G3), consisting of a bi-convex doublet (L7,8) and a single meniscus (L9) are axially movable in opposite directions to vary focal length whilst the group (G2) can, on its own, move further forward for close-up work. The fixed negative fourth group (G4) has a bi-concave doublet (L10,11) with positive cemented or non- cemented parting face (r17,r18).