Micro 4/3 lens adapters:
Nikon focusing helicoid

Focusing helicoid with male Micro 4/3 bayonet and Nikon F female bayonet. It extends from 27.25 to 38.37 mm by turning the scalloped ring. The lens does not rotate when the focusing ring is operated.

Pros: At its minimum length, this focusing helicoid allows focusing at infinity with Nikon F lenses. Useful to extend the focusing range of Nikon-mount lenses on Micro 4/3 cameras. Solid construction (heavier than other M42 and Micro 4/3 helicoids). The interior is threaded to avoid internal reflections. The ring closest to the Nikon mount operates a cam that connects to the aperture lever of the lens, and can be used as an aperture preset.

Cons: Black anodyzed aluminium rear bayonet, integral with part of the adapter body. Black anodyzed Nikon mount. The aperture preset ring is too imprecise to allow use to regulate the aperture of Nikon G lenses. When extending, the inner sleeve closest to the Micro 4/3 mount exposes a grease-covered surface that can be accidentally touched with one's hands. There is exposed grease also around the Nikon lens release button, where the aperture preset ring slides.