A convex lens is thicker at the centre than at the edges. Double-convex (DCX) lenses have two outward curved surfaces, a positive focal length and are useful for 1:1 imaging and in multi-element systems.
50mm and Larger Experimental Quality Double-Convex (DCX) Lenses are offered in several experimental grade options. Grade 1 is standard optical glass, edged, free of visible scratches, chips, stains, or oxidation. Grade 2 is unedged, non-optical glass, small chips, slight stains, or other defects. They may have slight edge cement separation.
Note: Specifications for experimental grade optics may vary as much as 10% from those listed. Also, no additional information is available other than what is provided.