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Pentax K1: Adapting Pentax 645 and Other Lenses to Pentax K

See my Pentax K1 wish list at B&H Photo.

Pentax Adapter K for Pentax 645 lenses

Back in February I wrote about Pentax lens choices, detailed below.

Several developments have occurred:

  • now offers conversion kits for Nikon F-mount lenses (those with aperture rings). Thus Nikon F, Zeiss ZF and ZF.2, Coastal Optics, Voigtlander and other brands can be modified to Pentax K mount. The modification requires changing the rear flange and removing about 0.2mm from a lever (to prevent physical contact internally). It should be reversible back to F-mount if not too much is taken off that lever.
  • One reader recently ordered the Cambo Actus Mini View Camera and states that Cambo has agreed to deliver a camera plate for the Pentax K1.

See also Pentax K1 Full Frame Lens Selection.

Lou F writes:

Do you have any idea yet if the K1 will accept my 645Z Pentax lenses via an adapter? If yes, which adapter?

My main concern with medium format adapters is the stress of putting a large and heavy lens on a fairly long lever arm (the adapter), resulting in excessive torque on the lens mount, including possibility of sag (tilt). For that reason, an adapter without a tripod foot isn’t a good solution in general, but there are exceptions for relatively smaller and lighter lenses, such as the Pentax 35mm f/3.5 (about 650g).

The flange focal distance of 45.46mm for Pentax K is ample given the 70.87mm flange distance for a Pentax 645 lens. In other words, there is a 25.41 inch delta—plenty of space to insert an adapter, and one with a robust tripod foot too.

At B&H Photo, the Pentax 645 Lens to Pentax 35mm K-Mount Body Adapter "K" is listed as “No longer available”, but it is listed as in stock at Amazon: 645 Lens to Pentax 35mm K-Mount Body Adapter "K". A google search turns up various other options.

The Ricoh Imaging site has an Adapter K for 645 Lenses page and various other Pentax K adapter question and answers. But it’s not clear whether the item is still available for purchase. Perhaps that will change given the release of the K1.

There are many adapters for lenses to Pentax K mount. B&H Photo lists a Pentax 67 Lens to Pentax 35mm K-Mount Body Adapter and Pentax Mount Adapter K for screw mount lenses. There are also lens adapters for Contax 645, Bronica PG, Bronica SQ and Rolleiflex 6000 to Pentax K.

Mount conversion is another option: Contax SLR and Leica R lenses can be converted to Pentax K mount via lens mount conversion at

Pentax K1

Collin O writes:

Here is what I received from my Pentax rep in early April regarding the Pentax 645 lens adapter:

“Yes it is still available but it only works properly with 645 lenses with aperture rings. So it will not work with the new D FA645 55mm F2.8, 90mm F2.8 Macro, 25mm or 28-45mm. It does work with the new D FA 645 35mm F3.5. The product code is 38455 Adapter K for 645 Lenses: 645 lens to 35mm K Bayonet Mount Body.”

DIGLLOYD: in general, I am not keen on lenses without aperture rings. Such lenses include Zeiss Batis, Nikon “G” lenses, Pentax as above, some but not all Sony lenses.

Lenses with aperture rings include Zeiss Loxia, older Nikon F-mount lenses, Zeiss ZF.2 DSLR lenses for Nikon and various others.

Scott S writes:

It's a lot of messing around. You can't leave it on a lens, for example I would like to leave it on my 80-160. You have to attach it to the camera first, then loosen a screw and rotate, then lock. Then you can attach the lens.

Mine got stuck during the attach phase, just wouldn't lock on, or come off.

Pentax are so stuck in the past providing "legacy compatibility" that they are not moving forward, at least that's the way it feels, plus the "loyal pentaxians" are so attached to technically shitty glass that has "character" that they can't see the sunshine from the rain.

I love my 645z and the results I obtain with it are superb, the K1 has potential, but like you say, they are all (ca-nikon-pentax) so attached to having a mirror and optical viewfinder that brings its own set of age old problems. It's no wonder Sony are kicking butt.

DIGLOYD: Indeed. Pentax optimal performance for the most part is marginal for the K1.

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