[Ed Hurst]

Hello all,

Does anyone know which mounts the registration distance of full frame Pentax allows us to convert? For example, I can convert Nikon mount lenses to run on a Canon, but not vice versa.

Most of the info. I can find about adaptors refer to the Pentax crop mount, which of course will not work the same way.

So will I be able to use Nikon mount lenses on the K1 with an adaptor? What about Contax/Yaschica mount? Obviously I mean while retaining infinity focus (and without the adaptor requiring optical elements).\

Thanks everyone!

Ed

[markkuk]

Pentax doesn't have any separate "crop mount". K-1 uses the same K-bayonet mount as Pentax APS-C DSLRs and film SLRs since 1975. The register distance is 45.46 mm.

[Sandy Hancock]

Pentax K-mount has a longer registration distance than either Nikon or Canon, so neither can be adapted properly to the K-1 without corrective optical elements.

Contax/Yashika is slightly longer, so they should work if an appropriate adaptor exists.

[Kunzite]

Actually, Pentax K has a longer registration distance than Canon EF, but shorter than Nikon F. The information is public and easily accessible, for example here:
Camera Mounts Sorted by Register

As for the OP's question: forget about adapting Nikon F to Pentax K lenses. The only way I'm aware of is by changing the camera's mount with a 3rd-party, which is something I wouldn't do on a brand new $1800 (or 2000 euro) camera.
If you want to use old lenses, look for K-mount ones.

[WPRESTO]

A thought that has occurred to me.
GIVEN THIS: Most very long lenses ( at least 300mm) are used for wildlife photography and therefore typically focused at modest distances, 100 yards or less. Substantial unit extension (=moving the entire lens) on a big telephoto is required to focus close, hence some unit-focusing lenses have very long minimum focus distances (I had a 300 f6.3 Takumar that had a MFD of 18 feet, useless for small birds).
CONSIDER THIS: There are CaNikon to K-mount adapters with internal lenses that allow focusing to infinity, basically weak telextenders with different mounts front and rear. But IQ degradation is almost always unacceptable (had one back in the 90's for mounting a Nikon 500mm on my LX - IQ not acceptable).
HOWEVER: there are no-lens adapters available that don't allow focus to infinity, but do not degrade IQ. Basically the lens is "pre-focused" to some near point, and the MFD is reduced. Using one of these, a lens such as a Nikon 600mm f5.6 EDIF that has a diaphragm ring might be a good choice for a birder, this lens being more readily available, less expensive in equivalent condition, and smaller/lighter than the 600 f5.6 Pentax. I've been tempted.

[boriscleto]

Pentax K-mount has a longer registration distance than either Nikon or Canon, so neither can be adapted properly to the K-1 without corrective optical elements.

Contax/Yashika is slightly longer, so they should work if an appropriate adaptor exists.

The registration distance of Nikon F-mount is 46.5mm, 1.04mm longer than K-mount and 1mm longer than C/Y-mount. Olympus OM is 46mm.

Replacement mounts exist for C/Y and OM lenses, but not for Nikon F. However, pre-AI F-mount can be force fit on K-mount. AI lenses need to be modified, and Nikon AF lenses won't fit unless you replace the lens mount on the camera.

[maxfield_photo]

m42 mount, but you probably already knew that.

[UncleVanya]

Adaptist makes a mount replacement for pentax dslr cameras that might interest you.

Adaptist - Home

[boriscleto]

Adaptist makes a mount replacement for pentax dslr cameras that might interest you.

Adaptist - Home

But are you really going to make an $1800 WR camera less than WR? An old film SLR maybe...

[WPRESTO]

But are you really going to make an $1800 WR camera less than WR? An old film SLR maybe...

Also, there is no positive lens catch to lock and hold the lens in position onto the body. So a careless twist when carrying and the lens hits the dirt, or pavement, or rock.

[boriscleto]

Also, there is no positive lens catch to lock and hold the lens in position onto the body. So a careless twist when carrying and the lens hits the dirt, or pavement, or rock.

Easily solved if you are willing to cut a new slot in the base of the lens. You can do the same when force mounting a Nikon lens, or when converting a M42 lens to K-mount...

[WPRESTO]

Easily solved if you are willing to cut a new slot in the base of the lens. You can do the same when force mounting a Nikon lens, or when converting a M42 lens to K-mount...

I presume you mean drilling a hole at the back of the M42 mount to engage the K-mount locking pin, then take an M42 to K-mount adapter, remove the catch spring that would hold it on the camera body, and permanently mount it on the lens with a little thread lock.

[bertwert]

I presume you mean drilling a hole at the back of the M42 mount to engage the K-mount locking pin, then take an M42 to K-mount adapter, remove the catch spring that would hold it on the camera body, and permanently mount it on the lens with a little thread lock.

I think that's what he means...

[boriscleto]

I presume you mean drilling a hole at the back of the M42 mount to engage the K-mount locking pin, then take an M42 to K-mount adapter, remove the catch spring that would hold it on the camera body, and permanently mount it on the lens with a little thread lock.

Of course. But the lens has to be wide enough...

[pde2000]

You can convert c/y mount lenses to K fairly easily (following Rio-Rico's advice on shaving). I have just finished adapting a yashica 28/2.8 ML so that infinity is available, but I had to remove about 0.2mm of the inner (registration) ring. Only 2 of the 3 bayonets engage with the pentax mount, and these have to be 'shaved' because of the slight difference in depth. I just do it by hand with a file. Once the mount engages with enough rotation to be secure a hole can be drilled to let the locking pin retain it. Having succeeded with the 28, i then did the 50/2ML which was also not quite getting infinity.

Although you can get proper replacement mounts from leitax that is expensive, and limited to newer mm lenses and a few ae. Also the screws that have to be removed first can be a right pain to move as they are glued in place. I have now adapted zeiss c/y vario-sonnar 80-200/4 (these are very cheap and good), sonnar 85/2.8 (very good but not quite so cheap), tele-tessar 200/3.5 (almost free and very good too) and planar 50/1.7 (great and cheap). The zoom and 200 needed no alteration to the register for infinity (the zoom is fully internally focused etc so the rear element does not move). For the sonnar I had to spin off the front cell, release a couple of locking screws and rotate the focus ring to bring a new infinity point to the helicoid - easy once you figure out how.

If I sell a few things then I will be able to buy a K1 to make full use of these zeiss lenses, which are far superior to the yashica ML - not that they are at all bad. The reason c/y lenses can be adapted so easily is that contax and pentax were partner businesses (there is a clue in the names). The first m42 mount was a zeiss design, and there was some collaboration over better coatings, but the contax stop down lever goes the opposite way to pentax, and sometimes needs cutting off to prevent it fouling (a bit drastic i know, but I wont go back to shooting film really, and there's no way I am getting a contax digital).