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01-12-2010, 07:31 PM   #1
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Pentax Km and old manual lenses: SMC Takumars & Tamron Adaptall 2 lenses

I have just bought a Pentax Km and would like to know whether I can use my Tamron Adaptall 2 lenses with it without short-circuiting the camera's electricals or damaging the camera in any other way.

If so, what Adaptall 2 mount must I get?

I should also like to use my Pentax Thread mount Super-Takumar 50mm and SMC 150mm lenses if I can find an adapter at an affordable price - which seems harder than I thought it would be.

I expect to have to select aperture manually on the lense mount and focus manually but would like to know if the iris will stop down to the pre-selected aperture automatically - as with e.g. the old K1000 and still older Spotmatic - or if I would have to stop down manually to the taking aperture..

If there is some way of using the through-the-lense meter that would be a bonus too, but I am quite prepared to find that I can't use the in-built light meter at all. I would still have use for the lenses.

01-12-2010, 08:46 PM   #2
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There should be no danger with an Adaptall adapter for K mount. I think there are but two adapters for adaptall - one with the PKA and PK (though i think the PKA is pricey). Get the one appropriate for your lens and pocketbook.

For the m42 screwmount:

https://www.pentaxforums.com/forums/pentax-lens-articles/3800-can-i-use-m42-s...unt-d-slr.html

On the Km you'll have to enter the menu: C > 3 > 19. Using aperture ring.

Change that setting to 2 to allow use of the aperture ring. This will have no effect on anything except manual aperture lenses. After doing that you can use the lens in manual mode. The light meter is triggered by the "AV" button. You can also use the Av mode, but you'll have to either short the topmost contact with some metal, or set +2 EV to compensate for the underexposure.

[edit] And yes, you'll have to be in manual on the lens so you operate the aperture. But the light meter will work no problem except for the underexposure I mentioned in Av mode.

Last edited by wasser; 02-02-2010 at 03:56 PM. Reason: bad wording
01-13-2010, 04:45 PM   #3
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Yes you can use M42 lenses on the Km. However you will need to use manual mode and the lens will have to be set on Auto for aperture. As the Km and all K mount bodies do not have the plate to push the pin that controls the aperture blades. Third party adapters have a plate but you lose infinity.

As for the adaptall you can get it to work with either a M42 mount adapter or a K mount adapter. However if you don't own the adaptall lens already and are looking to purchase one. I would advise against it as it isn't that good in sharpness or contrast. However if you already own one. You'd have to find the adapter for it. Shouldn't be too hard to find as any camera shop should be willing to give them away or sell them for pretty cheap.
01-13-2010, 06:22 PM   #4
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QuoteOriginally posted by epqwerty Quote
Yes you can use M42 lenses on the Km. However you will need to use manual mode and the lens will have to be set on Auto for aperture. As the Km and all K mount bodies do not have the plate to push the pin that controls the aperture blades. Third party adapters have a plate but you lose infinity.

As for the adaptall you can get it to work with either a M42 mount adapter or a K mount adapter. However if you don't own the adaptall lens already and are looking to purchase one. I would advise against it as it isn't that good in sharpness or contrast. However if you already own one. You'd have to find the adapter for it. Shouldn't be too hard to find as any camera shop should be willing to give them away or sell them for pretty cheap.
I think you meant the lens needs to be set to manual so you manually operate the aperture since the auto diaphragm doesn't function with the Km. Also, as I previously stated, you can use either manual or Av mode on the camera.

01-13-2010, 06:53 PM   #5
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QuoteOriginally posted by wasser Quote
I think you meant the lens needs to be set to manual so you manually operate the aperture since the auto diaphragm doesn't function with the Km. Also, as I previously stated, you can use either manual or Av mode on the camera.
Yes sorry I meant manual mode not auto on the lens. Thank you for the correction.
01-15-2010, 12:18 AM   #6
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Thank you for your replies and the trouble you have taken over them.

The lenses under reference are ones that I already have - Tamron SP 90mm and 500mm and Pentax 50mm and 150mm lenses so I should like to be able to use them if I can. These are all good lenses with 35mm film, the last is a real beauty and the 50mm at least gives me a fast lense for occasional use. I appreciate that the DSLR format is smaller and the designer providing only for the smaller angular coverage should be able to get a sharper image.

At present I have only an 18mm-55mm zoom lense for the DSLR which is a little short at the long end for "head'n'shoulders" portraiture. I use 105mm with 35mm film.

Last edited by Kendrick; 01-15-2010 at 12:22 AM. Reason: typo
01-15-2010, 01:32 PM   #7
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QuoteOriginally posted by Kendrick Quote
...The lenses under reference are ones that I already have - Tamron SP 90mm and 500mm and Pentax 50mm and 150mm lenses so I should like to be able to use them if I can...
Is that 500mm the f8 mirror lens? I just watched a couple on eBay go for pretty good prices. Anyway, for a mirror lens, you can get the cheaper PK adapter, because the lens only has one aperture. For the 90mm, it might be worth it to get a PKA adapter for the extra functions.
02-01-2010, 11:04 PM   #8
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Yes, the 500mm is the catadioptric lense and has only one aperture.

What are the estra functions of the 90mm which would make a PKA mount beneficial? Will the camera make the iris stop down automatically when the shutter is released?

02-01-2010, 11:25 PM   #9
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The PK and PKA adaptors should both stop the lens down automatically when shooting but the PKA adaptor reports aperture data to the camera body and allows for open aperture metering and other automated functions (aperture priority mode, P-TTL flash metering). You need to stop down to meter with PK lenses on digital bodies and on the K-m I believe you can only do that with the green button.
04-14-2010, 02:39 AM   #10
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I have not yet been able to obtain a Tamron mount for PK but have obtained a Pentax Screw adaptor and tried my 90mm lense. I encountered a difficulty. Something I have never noticed is that this lense mount has no control for setting the aperture to manual! Consequently there is no way to use the lense at any but full aperture! Not, that is to say, unless I am prepared to tamper with the workings of the mount. I guess it could be jammed in the stop-down position.

I can use my Takumar lenses and other Tamron lenses.
04-14-2010, 03:23 AM   #11
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Sorry to get to this thread so late - yes, the adaptall M42 does not have the auto/manual switch and therefore you're stuck wide open... unless you go and disable... erm... modify the mount to keep the aperture pin pushed in.

The regular K adaptall works like a SMC-M lens, the KA like a SMC-A, as described above.
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