[Raptorphotog]

I'm wondering where I might be able to find an adapter so that I can attach my K mount lens to my camera with a M42 screw mount. Any help is most appreciated. Thank you.

[Adam]

You cannot use/adapt K-mount lenses on M42 bodies, since the bayonet mount is physically larger.

[Na Horuk]

Yeah, it only goes the other way. You can get a genuine Pentax adapter or one of the others (usually online) to allow you to use m42 lenses like (Helios 44) on Pentax cameras (like K-50). But you cannot put a K-mount bayonet lens (like DA 18-55mm) on an m42 camera (like these).

m42 is the screw-mount, where the lens gets screwed into the camera, like a light bulb into a socket. it has 42mm diameter, where it also gets the name. K-mount is a more modern bayonet style mount, much faster to mount, and generally aligns more precisely to the body. The K-mount has a larger diameter, but requires the same register distance as m42 (distance between mount and camera sensor), which makes it really really difficult to adapt these lenses. An adapter would cost more than the lens, and it would reduce the image quality. Just not feasible. You can read up on register distance and its importance when trying to adapt a lens.

You can adapt both m42 and K-mount lenses to some Canon DSLRs, I think. Not sure what they allow, though, as I don't shoot Canon. I think you might need some lens modification (sometimes damages the lens), which Pentaxians don't really like. We want Pentax lenses to stay in good condition for Pentax cameras. Many people also adopt these lenses to Sony cameras, as those are very friendly to adapting all kinds of mounts. Note that adapting a lens usually blocks AF and possibly other functions. Just in case you are interested.

Good luck

[pathdoc]

The issue with Canon is that the aperture stop-down lever on K cameras fouls the mirror on a full-frame Canon body. The register distance is such that the lens will focus beyond infinity, and I vaguely recall one example of a Canon user shim one surface of his adapter far enough out that the aperture lever doesn't foul but the lens will still mount and give infinity focus.

The inability to use K mount lenses on my Spotmatics gripes me sometimes, but OTOH there's enough M42 lenses of all sorts out there that I'm spoiled for choice anyway.

[Thagomizer]

One possible option, would be to take a PK teleconverter and change the mount at the camera end to M42. I'm guessing that there are more good PK TCs than M42 ones out there. For macro use you can try the same trick with extension tubes; in fact practising on extension tubes (which are likely to be cheaper than teleconveretrs) might not be a bad idea). You'll lose light and image quality.

I never said it was a good solution....

[Lowell Goudge]

The issue with Canon is that the aperture stop-down lever on K cameras fouls the mirror on a full-frame Canon body. The register distance is such that the lens will focus beyond infinity, and I vaguely recall one example of a Canon user shim one surface of his adapter far enough out that the aperture lever doesn't foul but the lens will still mount and give infinity focus.

The inability to use K mount lenses on my Spotmatics gripes me sometimes, but OTOH there's enough M42 lenses of all sorts out there that I'm spoiled for choice anyway.

Why not add a KX to your cameras

[bertwert]

One possible option, would be to take a PK teleconverter and change the mount at the camera end to M42. I'm guessing that there are more good PK TCs than M42 ones out there. For macro use you can try the same trick with extension tubes; in fact practising on extension tubes (which are likely to be cheaper than teleconveretrs) might not be a bad idea). You'll lose light and image quality.

I never said it was a good solution....

That is actually not a bad idea...

[pathdoc]

Why not add a KX to your cameras

Because I have a Ricoh XR-1.

[Na Horuk]

But changing mounts is always messy. On lenses it can cause irreversible damage, on some lenses it will be simply impossible (if the back element is too big), and it might not be aligned parallel to the sensor once finished (ruining IQ). Even doing this to a teleconverter (TC) or bellows would be messy, but if you buy cheap you might not care if you lose it.
Only attempt this if you are really good with handcrafting and have all the needed tools

[Not a Number]

If you can find them with tubes the same diameter how about two sets of the very cheap extension tubes - the sort that have a screw on female mount on one and a screw on male mount on the other. One for K-mount, the other for M42 and just switch the female mount on the front. You can't get infinity focus and would have to use it as a close-up/macro lens but you never said you wanted infinity focus.

[stevebrot]

The issue with Canon is that the aperture stop-down lever on K cameras fouls the mirror on a full-frame Canon body.

Yep, and there are rear element clearance issues with some M42 lenses as well.

The register distance is such that the lens will focus beyond infinity, and I vaguely recall one example of a Canon user shim one surface of his adapter far enough out that the aperture lever doesn't foul but the lens will still mount and give infinity focus.

A proper adapter will provide the appropriate registration for the K-mount lens (will focus to, but not beyond infinity). While it may be possible to mitigate the lever interference by shimming, doing so will result in a loss of infinity focus. For K-mount lenses that foul the Canon mirror, available remedies include shaving the mirror on the body or removing the lever on the lens. Even with the lever removed, there may still be interference with the rear element and/or metal collars and such on a Canon FF body.

The inability to use K mount lenses on my Spotmatics gripes me sometimes, but OTOH there's enough M42 lenses of all sorts out there that I'm spoiled for choice anyway.

I guess the inability to use your K-mount lenses on M42 bodies is a little like not being able to use them on Canon R/FL/FD, Konica, Minolta SR/MC/MD, Topcon RE/Exakta, or Nikon F bodies of the same (1960s) vintage. Of course, most of those mounts are also not adaptable to M42 either.

It might be argued that Pentax "cut off" owners of M42 bodies back in 1975, though it might also be noted that SMC Takumar lenses continued to be available new for some years after the K-mount debuted with some focal lengths being exclusively M42. Non-Pentax makers continued to offer M42 lenses (cameras too!) for many years* and even to this day if you include Russian-made products.


Steve

* We can thank much of the lingering presence of M42 to the good folk at Cosina/Voigtlander and by extension, Carl Zeiss. Both labels continued to include M42 offerings until fairly recently (within last five years).

[pathdoc]

Even with the lever removed, there may still be interference with the rear element and/or metal collars and such on a Canon FF body.

Yeah, I came across that on YouTube yesterday; some Canon/Mirrorless-using guy was talking about the interference and in a later video he mentioned the Takumars' rear element also gave him problems on FF Canon bodies. Not all of them, though; he gave me the idea the 28/3.5 wasn't bothersome.

It might be argued that Pentax "cut off" owners of M42 bodies back in 1975

Pentax had to evolve to a bayonet mount with consistently repeatable lens-body spatial relations or die out. There are only so many electrical contacts you can make, for example, if you're not exactly sure where the lens is going to end up with regards to the body. Casual Spotmatic F and ES-II owners would have had no reason to update for some time, as they essentially already had K mount-like functionality with SMC Takumars, and the upgrade path for many of them would have been to the M series, on which their glass would work after a fashion, particularly on the ME and its descendants with their full-time Av mode.

It's indicative of the sway Pentax had back then that Ricoh and Chinon went with the K mount when they too switched. K-mount camera users may have to meter our Takumars stopped down, but at least with the K mount we don't have the AI/non-AI issue NIkon users have with their earlier glass.

[stevebrot]

It's indicative of the sway Pentax had back then that Ricoh and Chinon went with the K mount when they too switched. K-mount camera users may have to meter our Takumars stopped down, but at least with the K mount we don't have the AI/non-AI issue NIkon users have with their earlier glass.

Chinon only later (~1980). They stayed with M42 somewhat longer than the rest of the pack. The situation with Ricoh was more complex. The persistent rumor is that Pentax and Ricoh collaborated on on K-mount lens and camera design up through the early 1980s. The most celebrated example is the XR Rikenon 200/4 and Pentax-M 200/4 where the two lenses are essentially identical. Similarly, the XR Rikenon 28/3.5 (non-pancake) is optically identical to the Pentax-M 28/3.5, though not in the same lens barrel.


Steve

[pathdoc]

The persistent rumor is that Pentax and Ricoh collaborated on on K-mount lens and camera design up through the early 1980s.

"Oh Ricoh, don't you remember the heady days all those years ago when we did so much together? We can have that magic again, and more! Please, take me back - make me yours - Hoya's such a beast, I'd do anything to be saved from a lifetime at the hands of that uncaring monster!"

"Oh Pentax, yes. Come to me, be mine; together we'll do things Canon and Nikon can only dream of, and I'll give you fullness of frame the way Hoya never could. Wait here while I deal with him, and then we can be together at last."

XR Rikenon 28/3.5 (non-pancake)

This implies a Pancake version, does it not? How small? 40mm SMC-M small? *LBA starts to flare again*

[stevebrot]

This implies a Pancake version, does it not? How small? 40mm SMC-M small? *LBA starts to flare again*

Google: Rikenon 28mm f/3.5 Aspheric

-- or --

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/296363-rare-28mm-3-5-a.html


Steve