Converting k-mount camera to m42 -- permanently?

Lucius · Sep 26, 2023

Here's another one. I have a k-mount Chinon, which I want to use with my m42 lenses. The problem is that the k-mount adapter wobbles, which seems to be a common issue, at lest with the lenses I want to use it with the most. Reportedly some adapters sit more snugly than others inside the camera, but there is no way to tell without trying, and given their cost, it will be uneconomical to try several. So I'm thinking about gluing it permanently inside the mount (with super-glue?). I can think of a few things that can go wrong, so I'd appreciate if anyone has done precisely what I plan to and could share their experience!

chriscrawfordphoto · Sep 26, 2023

You would be better off buying a screwmount camera. Pentax Spotmatics are great user cameras and they're cheap. Using a camera made for m42 means your auto-aperture works, which it doesn't using a k-mount adapter.

Lucius · Sep 26, 2023

chriscrawfordphoto said:
You would be better off buying a screwmount camera. Pentax Spotmatics are great user cameras and they're cheap. Using a camera made for m42 means your auto-aperture works, which it doesn't using a k-mount adapter.

I have several m42 bodies, and I like some of them, but they have their limitations. In this case, I want to have a light-weight aperture-priority camera capable of 1/2000 shutter speed (the Memotron is too much of a brick for my liking, and I can't afford the Bessaflex, which, besides, doesn't have AE).

Kino · Sep 26, 2023

Why don't you make a thin, metal shim ring to eliminate the wobble and just leave the adapter on the camera at all times?

You can use a set of feeler gauges (sold in automotive repair stores) to get the thickness and buy appropriate shim stock from Ebay or your local industrial supply store/shop. It should be thin enough to cut a ring cleanly with sissors and an art knife. With this, you would still have the option to remove the adapter and a coat of light adhesive would keep the ring on the adapter.

Lucius · Sep 26, 2023

Kino said:
Why don't you make a thin, metal shim ring to eliminate the wobble and just leave the adapter on the camera at all times?

You can use a set of feeler gauges (sold in automotive repair stores) to get the thickness and buy appropriate shim stock from Ebay or your local industrial supply store/shop. It should be thin enough to cut a ring cleanly with sissors and an art knife. With this, you would still have the option to remove the adapter and a coat of light adhesive would keep the ring on the adapter.

That's an interesting idea, thanks!

Though if I understand this correctly, the shim would need to go on the camera mount, not the adapter. From what I've read (and seen), the adapter is supposed to sit loosely on its own, but should tighten up with the lens screwed in -- the lens's flanges are supposed to press against the camera's mount, while making the adapter pressing against it from inside (if that makes sense). Some lenses seem to be better at it than others (maybe different cameras behave differently too, not to mention different adapter makes). Definitely worth exploring -- I had actually thought of sticking some electrical take on the mount, but figured it would be torn by traction.

There is another issue though. The adapter is also intended to catch the lever that controls the diaphragm in native k-mount lenses (or rather it 'reads' aperture value and transmits it to the camera's electronics). By retracting this lever all the way back, the adapter puts it, so to speak, in the neutral position, allowing the camera meter accurately (at least in theory) with stopped-down m42 lenses. Now, one of the consequences of the adapter's wobbling is that this lever keeps changing its position, affecting metering: the shim might prevent this shifting once the lens is firmly attached, but the meter would need 'recalibrating' (with the ASA dial) every time the lens is changed. Can you think of a way around this?

Chan Tran · Sep 26, 2023

Lucius said:
I have several m42 bodies, and I like some of them, but they have their limitations. In this case, I want to have a light-weight aperture-priority camera capable of 1/2000 shutter speed (the Memotron is too much of a brick for my liking, and I can't afford the Bessaflex, which, besides, doesn't have AE).

Can you use the M42 lens on a K mount body with full aperture aperture priority?

Kino · Sep 26, 2023

Lucius said:
That's an interesting idea, thanks!

Though if I understand this correctly, the shim would need to go on the camera mount, not the adapter. From what I've read (and seen), the adapter is supposed to sit loosely on its own, but should tighten up with the lens screwed in -- the lens's flanges are supposed to press against the camera's mount, while making the adapter pressing against it from inside (if that makes sense). Some lenses seem to be better at it than others (maybe different cameras behave differently too, not to mention different adapter makes). Definitely worth exploring -- I had actually thought of sticking some electrical take on the mount, but figured it would be torn by traction.

I don't think I have ever run into an adapter that works that way, but I haven't been to every circus in town, if you know what I mean.

If that is the case, then you would have to make a custom shim for each lens that would fit down inside the adapter on the face of the mount and that would be prohibitively expensive in time and materials.

Lucius said:
There is another issue though. The adapter is also intended to catch the lever that controls the diaphragm in native k-mount lenses (or rather it 'reads' aperture value and transmits it to the camera's electronics). By retracting this lever all the way back, the adapter puts it, so to speak, in the neutral position, allowing the camera meter accurately (at least in theory) with stopped-down m42 lenses. Now, one of the consequences of the adapter's wobbling is that this lever keeps changing its position, affecting metering: the shim might prevent this shifting once the lens is firmly attached, but the meter would need 'recalibrating' (with the ASA dial) every time the lens is changed. Can you think of a way around this?

No, that sounds like a nightmare equal to creating custom shims for each lens.

This adapter sounds like it is more trouble than it is worth! I would try contacting a major supplier and explain this problem. Maybe they would be agreeable to letting you "try-out" adapters to find one that works properly; i.e., return them until you find the one that works.

xkaes · Sep 26, 2023

You just bought a crappy adapter. These are easy to find and cheap to buy. Just get another one. I have M42 adapters (basically thin T-mounts) to several bayonet cameras -- they are all around $10-20 and work fine because they are very simple with no aperture control. 42mm thread in the front -- different pitch than the T-mount -- and a bayonet on the back. No moving parts.

Lucius · Sep 26, 2023

Chan Tran said:
Can you use the M42 lens on a K mount body with full aperture aperture priority?

Not open aperture, no; you basically adjust aperture manually, and then let the camera decide what speed to shoot at.

Chan Tran · Sep 26, 2023

Lucius said:
Not open aperture, no; you basically adjust aperture manually, and then let the camera decide what speed to shoot at.

So you have to open the aperture up to maximum so you can focus easily then stop the lens down before you push the shutter release?

Lucius · Sep 26, 2023

Kino said:
I don't think I have ever run into an adapter that works that way, but I haven't been to every circus in town, if you know what I mean.

If that is the case, then you would have to make a custom shim for each lens that would fit down inside the adapter on the face of the mount and that would be prohibitively expensive in time and materials.

Not sure I follow, but the way I see it it just needs to make the mount a bit thicker -- I guess I would have to glue the shim to the mount anyway, making this a permanent modification.

Kino said:
No, that sounds like a nightmare equal to creating custom shims for each lens.

This adapter sounds like it is more trouble than it is worth! I would try contacting a major supplier and explain this problem. Maybe they would be agreeable to letting you "try-out" adapters to find one that works properly; i.e., return them until you find the one that works.

This seems to be a more or less ubiquitous problem, with only occasional reports of 'perfectly' fitting adapters (even authentic Pentax adapters have this wiggle room, though the Takumars seem better than other lenses at keeping tight, though not perfectly).

Lucius · Sep 26, 2023

xkaes said:
You just bought a crappy adapter. These are easy to find and cheap to buy. Just get another one. I have M42 adapters (basically thin T-mounts) to several bayonet cameras -- they are all around $10-20 and work fine because they are very simple with no aperture control. 42mm thread in the front -- different pitch than the T-mount -- and a bayonet on the back. No moving parts.

K-mount is a special beast -- the adapter has to sit completely inside the mount, to allow for infinity focus. There are flanged ones, and they sit tighter, but with these the lens doesn't focus to infinity.

Lucius · Sep 26, 2023

Chan Tran said:
So you have to open the aperture up to maximum so you can focus easily then stop the lens down before you push the shutter release?

The advantage of having a higher maximum speed is that it allows you shoot at or near the widest aperture more than otherwise. With a good viewfinder, it's usually not much of a problem focusing at f4 or even f5.6, and beyond that (if you ever need to go there), you have more than enough depth of field not to worry about precise focus.

xkaes · Sep 26, 2023

Lucius said:
K-mount is a special beast -- the adapter has to sit completely inside the mount, to allow for infinity focus. There are flanged ones, and they sit tighter, but with these the lens doesn't focus to infinity.

Thanks for that clarification, but are you saying that the OP DIDN'T get a DUD adapter?

There are over 100 M42 to Pentax K adapters on EBAY right now -- starting at under $5.

mshchem · Sep 26, 2023

Have you tried a genuine Pentax made adapter?

Lucius · Sep 26, 2023

xkaes said:
Thanks for that clarification, but are you saying that the OP DIDN'T get a DUD adapter?

There are over 100 M42 to Pentax K adapters on EBAY right now -- starting at under $5.

I'm not saying that, I'm saying that genuine Pentax adapters -- from what I could read online -- seem to behave in a generally similar fashion, at least regarding the former issue.

Lucius · Sep 26, 2023

mshchem said:
Have you tried a genuine Pentax made adapter?

No I haven't, but from the reports I've read, they seem to suffer from the same issue, and since they go for about the same I paid for the Chinon, it just makes more sense to 'sacrifice' the camera by permanently modifying it than to spend £20 on an adapter that may work no better.

dynachrome · Sep 26, 2023

I have a number of original Pentax adapters and they all work well. I also have some off-brand ones, which are not always perfect. For my Mamiya Auto XTL cameras I have both types of P adapters. These allow me to use M42 auto diaphragm lenses with stop down metering and auto diaphragm operations. I have a fleet of Pentax Spotmatics which have been overhauled by Eric Hendrickson so I have plenty of cameras for my Takumars and other M42 lenses.

Lucius · Sep 26, 2023

dynachrome said:
I have a number of original Pentax adapters and they all work well.

Do they work the same on both Pentax and third-party bodies, with both Takumar and other brand lenses? Is there absolutely no wiggle? Do they have any adverse impact on metering? I haven't tried all possible combinations, but my adapter seems to be behaving much better on my ME Super with a Takumar than on the Chinon body with a Chinon lens. My suspicion is that this may be down to the body and/or lens, rather than to the adapter as such.

dynachrome said:
For my Mamiya Auto XTL cameras I have both types of P adapters. These allow me to use M42 auto diaphragm lenses with stop down metering and auto diaphragm operations. I have a fleet of Pentax Spotmatics which have been overhauled by Eric Hendrickson so I have plenty of cameras for my Takumars and other M42 lenses.

What's the advantage of the XTL over the (natively m42) DSX? I recently got myself a Mamiya NC1000 with a P adapter, but haven't decided yet if I like it... I have a few Spotmatics, Fujicas and m42 Chinons, but if one wants higher speeds in a compact body (plus auto-exposure), there isn't much to choose from.

mshchem · Sep 26, 2023

Maybe try gluing one to one of your least favorite bodies. I would get some serious Henkel industrial adhesive. Not sure what the Chinon lens mounts are, gluing metal to metal is probably easier than metal to plastic. Of course if you use a thick paste adhesive it may just lock it in place. Me, I think I would find different combinations of bodies, and adapters.

Paul Howell · Sep 26, 2023

I have a Pentax branded adaptor, have used it in my K1000, SF1, and PZ1 without issue. But if I want to shoot M42, (well sometimes I use my Spot for grins) I use my Chinon CE and CM 3. The CE 3 allows for aperture preferred exposure with single pin M42, and it takes a crappy and slow winder.

Väinö Louekari · Sep 27, 2023

I also have a Pentax adptor that works fine, no wobble or any other issues.

neilt3 · Sep 27, 2023

Would it not be possible to obtain the m42 lens mount off a scrap m42 camera and replace the K mount off your Chinon with it ?
If the metal flange on the Chinon is the same thickness ( for infinity focus ) you might only need to redrill the holes if differently positioned.
You've no aperture linkages to worry about , so it might just be a straight swap .

Lucius · Sep 27, 2023

mshchem said:
Maybe try gluing one to one of your least favorite bodies. I would get some serious Henkel industrial adhesive. Not sure what the Chinon lens mounts are, gluing metal to metal is probably easier than metal to plastic. Of course if you use a thick paste adhesive it may just lock it in place. Me, I think I would find different combinations of bodies, and adapters.

I only have two k-mount bodies Basically I've tested more or less all m42 bodies (at least among those that had some promise in my eyes), so now I'm trying to figure out what non-native options to shoot m42 lenses there are that might give some specific advantages over native bodies. But if this proves prohibitively complicated, it won't be the end of the world.

But it's a good point about using a thick adhesive -- I was thinking about super-glue, but it might seep where it's not wanted.

Lucius · Sep 27, 2023

Paul Howell said:
I have a Pentax branded adaptor, have used it in my K1000, SF1, and PZ1 without issue. But if I want to shoot M42, (well sometimes I use my Spot for grins) I use my Chinon CE and CM 3. The CE 3 allows for aperture preferred exposure with single pin M42, and it takes a crappy and slow winder.

I have CE, CE3, CM3 and CS4, besides the k-mount CE4s; of the m42 mount ones, only CE is capable of 1/2000 shutter speed, but it's too heavy.

Väinö Louekari said:
I also have a Pentax adptor that works fine, no wobble or any other issues.

I now did a little more testing, and my adapter fits the ME Super just fine. With a Takumar, it tightens up nicely, and doesn't shift when focusing or adjusting the aperture. With more pressure, it does move in circle about one mm, but this doesn't seem to affect metering.

On the Chinon, and with the same Takumar, it's positively wobbly, and I have the impression that its wiggle room is a bit more than a mm. Also, the meter reading changes by about a stop between the extreme positions.

So basically it seems to be the Chinon's issue, not the adapter's, and since this is a Pentax mount, I doubt I can find an adapter that will fit the Chinon, other than by chance.

Converting k-mount camera to m42 -- permanently?

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