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10-06-2012, 09:39 PM   #1
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how to tell compatible lenses

I have been going to some thrift stores and pawn shops lately, and have seen lots of old lenses. Can someone give me an idea of how to spot by looking which lenses are compatible with the K mount, either natively or with a generally available adapter? Thank you for any input you can provide.

10-06-2012, 09:52 PM   #2
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There are many mounts that at a glance look similar to Pentax K, so without really knowing the layout of the mount it can be hard to tell. The best thing I could suggest doing is picking up something cheap and pocketable that has a K mount on it, like an old teleconverter or extension tube, then you can physically try it. Eventually, if you do this a lot, you'll learn the subtle difference between mounts, like the aperture couplings and location of the lock pin slot.

You can mostly rule out adapters except for M42, which is the most common screw mount, so if you find something with a screw thread it is likely to be M42. Almost everything else won't reach infinity on a Pentax body with an adapter that isn't optically corrected and getting an optically corrected adapter isn't really worth the trouble.

Beyond that you get into physical modifications to adapt lenses, which can be easy with certain ones, but not something I would recommend attempting unless you know what you're doing.
10-06-2012, 09:55 PM   #3
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Simplest way is to buy a cheap set of k-mount extension tubes or an old tele-converter in k-mount. Take it with you to the thrift shop and try the lens. If it fits, it works.

Less simple, if it says Pentax on it and is a bayonet mount, not screw mount then it works. If it is not a Pentax lens look for 'K' or 'K/R' on it.

Be aware that not all k-mount will work without issues. Ricoh used the k-mount for their cameras back in the film days but they also added a pin called a "Ricoh Pin" which can sometimes get stuck on Pentax cameras.

That is the short version, it is a lot more complicated than that sometimes but that should get you by 90% of the time. Stick with Pentax brand and you are fine 100% of the time.
10-06-2012, 09:59 PM   #4
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QuoteOriginally posted by jatrax Quote
Stick with Pentax brand and you are fine 100% of the time.
Unless you happen to find an Auto 110 lens, but those are really small, so it should be fairly obvious.

QuoteOriginally posted by jatrax Quote
If it is not a Pentax lens look for 'K' or 'K/R' on it.
Avoid K/AR though, because that is Konica. R-P/K should be fine, but check for the Ricoh pin on anything with an R, P/K-A is good too and will give you full auto metering.


Last edited by elliott; 10-06-2012 at 10:11 PM.
10-06-2012, 11:19 PM   #5
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QuoteOriginally posted by jatrax Quote
Simplest way is to buy a cheap set of k-mount extension tubes or an old tele-converter in k-mount. Take it with you to the thrift shop and try the lens. If it fits, it works.

Less simple, if it says Pentax on it and is a bayonet mount, not screw mount then it works. If it is not a Pentax lens look for 'K' or 'K/R' on it.

Be aware that not all k-mount will work without issues. Ricoh used the k-mount for their cameras back in the film days but they also added a pin called a "Ricoh Pin" which can sometimes get stuck on Pentax cameras.

That is the short version, it is a lot more complicated than that sometimes but that should get you by 90% of the time. Stick with Pentax brand and you are fine 100% of the time.
It is fairly simple to remove the "Ricoh pin". I've done that on the Craig Optics 28-70 that I've owned since the mid-80s so that it works on the Pentax digitals.
10-07-2012, 02:37 AM   #6
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Hi,

do you know this internet page ? Pentax K-Mount Lenses and Lens Accessories

Regards
Michael
10-07-2012, 10:18 AM   #7
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QuoteOriginally posted by jatrax Quote
Be aware that not all k-mount will work without issues. Ricoh used the k-mount for their cameras back in the film days but they also added a pin called a "Ricoh Pin" which can sometimes get stuck on Pentax cameras.
This caution cannot be understated. Despite assurance from various forum members, the "Ricoh Pin" hazard is a serious potential hazard. Unfortunately, the degree of peril is difficult to gauge without some experience with the mount. It is enough to say that in the worst case some Ricoh-variant K-mount lenses may be almost impossible to remove from a Pentax AF body (both film and digital) once mounted.

I would suggest avoiding the following:
  • Rikenon-P (all models)
  • Lenses marked PK/R on the barrel or the mount
  • Lenses marked KR
  • Lenses marked PKA/R
  • K-mount lenses with "P" on the aperture ring rather than "A"
Other Rikenon/Ricoh lenses are perfectly safe.

The "pin" itself is sometimes an actual pin and other times a ball-contact. In both cases it is spring loaded and unfortunately has the same position on the mount as the Pentax AF screw drive. When mounted, the pin drops into the screw-drive well from which it may not be easily retracted. The ball type is much less prone to jamming than the pin type.

Note that Pentax developed its AF bodies some years after the Ricoh mount went to market, so this is a black mark against Pentax.


Steve


FWIW...rescuing a body with a jammed Ricoh pin usually involves careful use of an automotive feeler gauge slipped into the mount space between the lens and body. In one particularly bad case, the services of a repair shop were needed and the lens was subjected to a hack saw to cut it off the camera. The user then had to also pay to have the mirror box thoroughly cleaned to remove the shards.
10-07-2012, 10:21 AM   #8
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QuoteOriginally posted by eastman Quote
It is fairly simple to remove the "Ricoh pin". I've done that on the Craig Optics 28-70 that I've owned since the mid-80s so that it works on the Pentax digitals.
Yes, it is but explaining how and why to someone who is still trying to figure out what a k-mount looks like may be more than they were looking for. Plenty of non-ricoh pin lenses out there to play with until they have more experience.

10-23-2012, 10:08 PM   #9
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a follow up question i have is what is meant by a bayonet mount? I saw a post for a lens on craigslist that referenced a bayonet mount, but also saw some people on this site talking about the lens. I assume this would require an adapter to mount on a K-mount, but where can you find that adapter? Any input is welcome...Thanks.
10-23-2012, 10:14 PM   #10
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QuoteOriginally posted by toukan Quote
a follow up question i have is what is meant by a bayonet mount? I saw a post for a lens on craigslist that referenced a bayonet mount, but also saw some people on this site talking about the lens. I assume this would require an adapter to mount on a K-mount, but where can you find that adapter? Any input is welcome...Thanks.
Bayonet mount is a generic term, many cameras use a bayonet style mount, Pentax, Olympus, Nikon, Canon, Minolta and many, many others. Without knowing specifically which bayonet mount it is, it is impossible to know what it is compatible with.
10-24-2012, 07:32 PM   #11
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QuoteOriginally posted by toukan Quote
require an adapter to mount on a K-mount,
K-mount is a bayonet mount. It basically means you push the lens in and turn a bit and it locks. AFAIK all modern lenses are bayonet so it is a little confusing. Back in the day all lenses were screw mount and bayonet was the new kid on the block so you had to be specific.

As noted though just because it is bayonet does not mean it works with your bayonet mount, it still has to be k-mount.

And in general it is not worth getting adapters from other lens brands to Pentax. The other way, yes. Pentax can be used on most others mounts with an adapter. This is due to the registration distance of the mount. Pentax is relatively long. So it is easy to use a Pentax lens on Canon very hard to use Canon glass on Pentax. It can be done with an optical adapter but this degrades the IQ so not usually worth it.
10-24-2012, 08:54 PM   #12
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Be aware that some lenses have changeable mounts on them so although the one in the shop might be cheap because it has an unknown mount you may well be able to put a Pentax mount on it. It is worth learning about these as I have a number of nice lenses that came with other than Pentax mounts. Adaptall is one example of an interchangeable mount system, but I assume there are others.

M42 is an easy mount to use with Pentax K cameras and it was at one time a standard Pentax mount, the point is you might come across really nice M42 lenses which are carrying M42 adapters for other camera types in which case all you have to do is take that old adapter off and put a Pentax K-M42 adapter on.

Google is your friend.

John
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