[LowVoltage]

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

---

A DIY lens experiment continues, and one of my investigations involve those novel pieces of machined aluminum, the reverse K-mount adapter. Like so many other accessories, these things are plentiful and cheap on eBay. The infamy of knock-off M42-to-K adapters for getting stuck on DSLR bodies makes me wonder if anyone has an opinion about the K-mount half of the reverse adapters. If any of you have had experience with the reverse adapters, can you say one way or the other if the K-mount portion has caused issues with your camera?

It seems the M42/K adapters have trouble with the small metal flap malfunctioning or some other thing (this leads me to believe if any of the third party adapters are any good). However, the reverse adapters don't appear to have the extra metal flap. Any issue with the precision of the mounting distance is less of a concern because these things are used for macro photography.

And while I'm on the subject of anything K-mount knock-off related, my eBay trolling showed me this K-mount bellows. Naturally, they don't show the mount end of the bellows, so who knows what to expect there.

For what it's worth, I'll mention that the bellows could potentially be used in conjunction with the reverse adapter. Basically, I need a focusing method to move a "lens" made from loose elements and filter rings to-and-from the sensor plane. I'm considering some helical focusing extension tubes. Because these use M42 mounts I would need an M42/K adapter and I'm not willing to jeopardize my camera body with a knock off adapter. The real deal is either hard to find or ridiculously expensive. My experiment is getting more and more costly, so if I don't have to by the M42/K adapter at all then I'd be happy.

[Giklab]

Just how 'costly' is it getting? I'm at around 40€ ATM.

[G and T]

It seems the M42/K adapters have trouble with the small metal flap malfunctioning or some other thing (this leads me to believe if any of the third party adapters are any good).

While this may be true of some of the M42 adapters, it only affects third party infinity focus adapters. If your project doesn't need infinity focus,ie macro, why don't you use a flanged non infinity focus M42 adapter, I've never heard of one of these being stuck on a camera body and they are usually even cheaper than third party infinity focus adapters.
Glenn

[pacerr]

OK, once again.

The M42 adapters don't get 'stuck' on cameras - they were originally INTENDED to be semi-permanently mounted on the camera so that a pro's expensive collection of M42 lenses could be safely and securely used on the new K-mount bodies during a transition period. They work fine when used as intended.

Today, many folks attempt to use the adapters to make K-mount lenses out of M42 lenses despite the presence of the designed latching mechanism. Adapters can be easily removed if you read the instructions unless they're very poorly machined knock-offs which can be a PITA.

If you wanna make K-mount lenses, simply remove the spring clip and accept that the lens won't be securely latched in the body.

Those despised flanged adapters were simply a compromise attempt to provide a secure lens latch notch with a trade-off of loosing 10-20% of longer range focus distance. The ~ 0.7mm of "extension tube" effect works great for macro, close-up and studio shooting - just not for landscapes at infinity.

Appreciate the intended use of the adapters and make lemonade.

[LowVoltage]

Just how 'costly' is it getting? I'm at around 40€ ATM.

I haven't totaled everything up since I'm still trying to decide on an appropriate base for everything. However, I'm beginning to get a picture of the general expenses of the project. A budget of around $100/£60 seems likely. The precision/quality of the elements will have an impact on cost, though not to a huge degree. Another thing I need is a collection of empty filter rings and step-up/step-down rings. The empty filter rings aren't common, and seem to be unnecessarily expensive. The step-ups are cheap, though.

[Giklab]

Maybe searching for UV filters sold in lots would help. then you could just take out/break the glass.

[LowVoltage]

Maybe searching for UV filters sold in lots would help. then you could just take out/break the glass.

Yeah, I've done some cursory searches for junk filter lots - and it's weird, because I've come across individual filters with slots in the retaining rings like one would find on a camera lens. These are perfect for getting rid of the glass, but they never seem to be in the size I'd like. On the other hand, I have one or two Haze/UV filters with glass held in with who-knows-what, but it's certainly not any kind of typical retaining ring. I'm hoping to do some kind of post on this when it's all done (and successful).

[LowVoltage]

OK, once again.

The M42 adapters don't get 'stuck' on cameras - they were originally INTENDED to be semi-permanently mounted on the camera so that a pro's expensive collection of M42 lenses could be safely and securely used on the new K-mount bodies during a transition period. They work fine when used as intended.

Well I'm certainly glad you brought this up, because I've never heard this explanation before. However, it did bring me to a head-slapping "duh" moment while I was out for a ride. I didn't bother to mention, once upon a time, I did own an authentic Pentax M42/K adapter. And although it seemed I had to have at least one long fingernail, removal was simple enough. Nobody ever mentioned to me the use of the adapter strictly as a bridge between a new body and a user's likely extensive collection of legacy glass. The only M42 lens I had at the time was a 300mm tele-Takumar.

Anyway, the moment of clarity only presented itself when I realized the non-infinity focus adapters didn't have the flange because they had the slot for the K-mount locking pin. I simply didn't get the fact that a K-mount anything didn't have a flange because it simply wasn't necessary, that the true infinity-focus adapters were the only creatures to have the bit of metal because they couldn't provide the locking pin slot between adapter, body, and lens. Ok, derp moment has passed - I was focusing too much on people's cries of foul play with crummy knock-offs (and some really do appear to have major issues apart from the flange) to realize I didn't even need those adapters for my project.

I did end up ordering a K-mount bellows and the requisite reverse K-mount-52mm adapter so I could start mounting filter rings on the end. At some point in the future I might adapt the project to macro helical focusing adapters simply for the sake of slimming things down.

[Doundounba]

FWIW, I just received two k-mount to 52mm reverse mount adapters from China via a reputable seller (99.6% feedback rating), and I wouldn't put them directly on my camera body. I intend to always use them on (at least) a short extension tube, because the adapter can require a fair amount of torque to remove it from the mount, and it's so thin that it's hard to get a decent grip on it... That way if it gets stuck on the tube, it's not a huge deal.

[LowVoltage]

FWIW, I just received two k-mount to 52mm reverse mount adapters from China via a reputable seller (99.6% feedback rating), and I wouldn't put them directly on my camera body. I intend to always use them on (at least) a short extension tube, because the adapter can require a fair amount of torque to remove it from the mount, and it's so thin that it's hard to get a decent grip on it... That way if it gets stuck on the tube, it's not a huge deal.

Thanks for sharing your experience. I'm trying to power through my usual anxiety and "just do it", but I'm also trying to be sensible and ask about kit I haven't used personally to see if there's something I should be aware of. I mentioned it before, but I am going to be using a K-mount bellows and then put a reverse-K on the end of that. Hopefully, the bellows bayonet will be a good match. To boot, there's plenty of surface area on the bellows to grapple with. Since the reverse adapter isn't meant for the camera body in my project I won't mind if the machining precision is off a bit...

...but I'm keeping my fingers crossed that everything will be just fine!