Adapter advice.


Link Posted 05/06/2023 - 15:37
Help please. Any advice on the purchase of an M42 to Pentax K Adapter. Seems to be plenty out there but I would like thoughts on a decent one. Regards to all. (for SMC 55mm 1.8 Takumar)
Just passing thru
Last Edited by takuman on 05/06/2023 - 15:42


Link Posted 05/06/2023 - 16:13
The genuine Pentax 'Mount Adapter K'. The old Part No: 30120. I have the original Pentax instruction leaflet in front me which states that " This adapter is used to attach the conventional TAKUMAR screw-mount lens to the PENTAX K mount camera" (end of quote!). The photographs, rather surprisingly, show how you need to use a ball-point pen to mount and dismount the adapter...not too hard to find (ebay etc) but getting pricey. I have tried Chinese copies and have had them jam in place, so I do not recommend using them..



Link Posted 05/06/2023 - 19:27
Roger many thanks for your reply and advice on the original part No. Regarding the use of ball-point pen I have read that elsewhere, however I believe there is a Pentax tool for this. The search commences, e-bay here I come. Regards John
Just passing thru


Link Posted 05/06/2023 - 20:40
Hi takuman,

Here's my take on this.

If you look at the K mount lens the red dot on the mount is aligned with the focus red line on the lens body.

My experience is that there is an advantage with paying for a genuine Pentax adapter as then the aperture and focus points on an attached lens line up correctly with the camera body i.e. they are at the 12 o'clock position. Here's an example using a genuine Pentax adapter with M42 lens, a Helios 44-2, showing the red dot and that it aligns correctly.

With a cheaper cloned adapter they fit but the lens no longer lines up at the 12 o'clock position. You can tell whether the alignment is correct as the adpaters have a red dot on them. When the Pentax made adapter is fitted to the M42 lens the red dot on the adapter aligns with the lens' red focus position mark. With a clone copy adapter these re marks don't align. Again using the Helios 44-2 lens now with the cloned adapter.

Note I have removed this adapter's spring locking tab.

Things get more complicated when using a M39 lens, I have an Industar-50 lens with a M39 mount. To use this lens I have to fit a M39 to M42 adapter (non Pentax) and my genuine M42 to Pentax K adapter. Using this combination the lens and adapters can now be fitted to the camera but does not align correctly. I don't know if a genuine Pentax M39 to M42 adapter is available, but if this exists perhaps the lens would have aligned correctly.

A couple of notes:

I have had adapters get very tightly attached to the lens, if this happens fit a lens cap on to the adapter and rotate it anticlockwise to release the adapter from the lens body.

Also I have tried another cloned M42 - PK adapters and again this did not align correctly but the misalignment was not the same.

Hope this helps.



Link Posted 05/06/2023 - 21:03
I had a bad experience with a cheap adapter getting stuck. Luckily, I was trying it in a used camera shop and their tech was able to release it from my K200D, but still, the experience put me off M42 lenses for a couple of years. Since then I have only ever touched the genuine adapters and have never had a problem. I'm sure I own three but one seems to have gone walkies.
Pentax hybrid user - Digital K3, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X and Panasonic L digital
Fan of DA limited and old manual lenses


Link Posted 05/06/2023 - 22:25
If you bite your nails then you are out of luck and will need a ball point pen. Otherwise, the genuine adapter can be removed by sticking your thumbnail into the slot at the 10 o'clock position to release the spring. Do not over tighten the lens to get the index mark precisely lined up (it's tempting when it's half a degree out). It will be a bugger to get off again! Putting the thing onto the camera, it is 'obvious' that you shove the red dot to the red dot and then try to push the opposite side of the adapter into the mount. Surprise - it won't go. Think about it and ignore the dot (other than for positioning it). The spring has to be compressed before the rest of it will go into the mount so shove the bit with the spring in first. The remainder simply slots into place.
Some M42 mounts - like Tamron twin tele, Meyer 135 and 200mm, Tair 300mm do not snug up to the camera when screwed on and they leave a tiny gap where the two slots on the adapter will admit light. It doesn't always happen but when it does it can be very hard to diagnose the problem. Once you realise where the light is getting in a tiny bit of tape cures it instantly.
Both the *istDS and the K5 are incurably addicted to old glass

My page on Photocrowd - link


Link Posted 06/06/2023 - 07:37
So much knowledge out there. Thank you all. I have sourced Part No: 30120 on you know where, news will follow when it arrives. Many thanks.
Just passing thru


Link Posted 06/06/2023 - 08:20
I've used a bunch of third party adapters with the springs removed - never with the spring. You simply keep a K mount rear cap available to screw the adapter on and off your M42 lenses.

As along as the adapter is tightly screwed onto the lens you'll have no problems using it like any manual K mount lens.

I've also had the genuine adapter but it's a bit of a faff getting it on and off while still using K mount lenses compared to keeping a few adapters ready to 'convert' lenses.
All the gear with no idea


Link Posted 06/06/2023 - 17:28
I have read that some users leave the adapter attached to the lens, is this feasible as this is my only M42 lens (unless another catches my eye). Thanks for your response HarisF1.
Just passing thru


Link Posted 06/06/2023 - 23:06
It can be done but sooner or later you will remove the lens and the adapter will stay in the camera. It can be more trouble than you might expect. Once you get used to it you will almost certainly get more lenses from E bay - M42s are not expensive and it's fun to try them out.
Both the *istDS and the K5 are incurably addicted to old glass

My page on Photocrowd - link


Link Posted 07/06/2023 - 00:06
davidwozhere wrote:
It can be done but sooner or later you will remove the lens and the adapter will stay in the camera. It can be more trouble than you might expect. Once you get used to it you will almost certainly get more lenses from E bay - M42s are not expensive and it's fun to try them out.

It's actually easier to remove the adapter from the camera body if the little metal spring plate has been removed which will be necessary to do if the adapter is to be permanently fixed to the lens. The big caveat is that if using a lens with a stiff focus ring (a common downside found on vintage M42 lenses) then one can if not careful, unwittingly dismount the lens from the the camera whilst focussing, so care is needed. That aside, the purchase and enjoyment to be found in using a vintage M42 lens can lead to a long term addiction. You have been warned!
C.O.L.B.A.S victim
(Compulsive Obsessive Lens Buying Addiction Syndrome)

What you need are lenses, more lenses, bigger lenses, better lenses, faster lenses, vintage lenses and when you have these, your pictures will be perfect!


Link Posted 07/06/2023 - 09:58
Thanks again for further advice. As I hope to find more M42 lenses, depending on how I get on with this one, camera mounted adapter seems best option. I think!
Just passing thru


Link Posted 07/06/2023 - 12:13
An interesting thread on a number of levels. Not only technical, but takuman says, 'so much knowledge out there.' And so freely and generously given. Just one of the reasons I really like this group.
Be well, stay safe.


Link Posted 07/06/2023 - 17:52
Genuine Pentax adaptor and I use one of the demounting tools supplied with the cheap chinese adaptors to remove it better than a ball point pen.Although the japan made adaptors that Jessops used to sell are quite decent


Link Posted 07/06/2023 - 21:11
It's like rolling a snowball, you ask a question and the answers then come rolling in. Thank you each and everyone of you. Kind regards, John
Just passing thru
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