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Difference between PK an K extension rings

Harry Joseph , Aug 12, 2012; 10:37 p.m.

Does anybody know the difference between the old Nikkor PK(Pk 11, PK13, PK14 etc) extension rings and the K (K1, K2, K5 etc) extension rings and are they interchangeable ?


Michael R. Freeman , Aug 12, 2012; 10:51 p.m.

The PK rings are Ai compatible, ie. meter coupled and auto-diaphragm.

The K rings are not meter coupled (stopdown metering is required), are not auto-diaphragm (finder dims as you turn the aperture ring) and are stacked together for various extensions. Some of the K rings can not be used on modern bodies.

The K1 ring can be used on most modern bodies, and is an excellent extension ring for up close work with manual focus wide angle lenses. It's the thinnest F-mount extension ring available (5.8mm).

Michael R. Freeman , Aug 12, 2012; 10:53 p.m.

Some info on the K ring set:

Michael R. Freeman , Aug 12, 2012; 11:03 p.m.

The K2 ring is usually listed as "incompatible" with modern Ai film and digital bodies. Not sure of the exact reason for the incompatibility, but apparently it should not be attached directly to the camera body mount.

I suspect it would be okay used in a stack as long as the K1 is mounted between the body and the rest of the ring(s).

Harry Joseph , Aug 13, 2012; 04:51 a.m.

Thank you all.

Sem Svizec , Aug 13, 2012; 08:20 a.m.

The K1 ring is very tight on lens electrical contacts. Mount lenses with extreme care, better shave some brass off the ring in the affected area. Is great for wide-angle close-ups, a deep-focus thing if you don't mind a bit of diffraction.
Otherwise, the K set is useful with reversed lenses with the BR-2A adapter, because there is no automatics left to lose ;) Here extension also increases magnification, and may improve quality (mind a bare reversed lens is used closer than its Min Focus Distance).

Harry Joseph , Aug 13, 2012; 08:51 a.m.

Yes Sem I heard allot about the K1 especially when coupled with the 20mm f3.5 which I own. I have a set of PK 11, PK13 and I think PK14 but I wasnt sure about the K1. I bid on a listing on eBay for a set of K1-K5 but lost out in the last few seconds.
The entire set sold for $32 my highest bid was $29.99. Then I saw a sole K1 that was selling for $19.99 so I purchased that. Maybe I won't miss the rest of the tubes since according to Michael you have to stop-down with them.

Michael R. Freeman , Aug 13, 2012; 09:02 a.m.

If you already have the PK-11/12/13 extension rings, the K1 is probably the only one from the set that would be of any practical use to you anyway. I have the K1 ring, but not the rest of them.

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