Nikon Series E 50mm f1.8 back but honestly you can use

but honestly you can use it for pretty much whatever you'd like

The Asahi Pentax L Adapter B adapts M42 thread mount lenses to the Leica thread mount

5mm) designed to increase magnification for close-up work

diaphragm control is a touch stiff

This Nikon 18mm f2

Nikon Series E 50mm f1.8 back but honestly you can useThe Nikon Series E 50mm f1. 8 lens is a compact almost pancake lens (french toast lens?) with a fast f1. 8 aperture. It is compatible with film and digital Nikon F mount cameras (though function will vary). In good condition, with light cosmetic paint and finish wear, some internal dust, smooth focusing and good diaphragm.