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07-13-2011, 01:51 PM   #1
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Why did Pentax make using M42 leneses so awkward?

I have an old Yashica camera. It has a yashica/contax mount, so I have also aquired an M42 adapter. Using it is as easy as it could get. I just screw it on a M42 lens and get a y/c mount lens with infinity focus and no additonal glass. The adapter even pushes down that pin on automatic aperture lenses.

When I want to use M42 lenses with K-mount, I have to use a tool to insert a ring into the mount. The whole process is very inconvenient and takes time. And if i want to use the aperture on automatic M42 lenses, I need to disassemble the lens and find a way to fix the pin.

My question is why did Pentax make using M42 lenses on K-mount so difficult if it could be so much more convinient for many Pentax users.

07-13-2011, 01:59 PM   #2
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Actually, I think you will find, that they weren't original manufactured for K usage. They were fine for what their intended usage was, screw mount.

Yes they are awkward, but if we wish to use them on our DSLR cameras, then adaption is the only way.

I agree, yes awkward.

The burden we have to bear to use some of these great old lenses.

I leave my adapter firmly attached to the lens, saves a lot of hassle. even if it means owning 1, 2 or more adapters.
07-13-2011, 02:02 PM   #3
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Well ive heard that the third party adapters stays on the lens and not the body. As for the official one it is body mount. I think the reason behind this is because they were thinking people using the m42 lens mount have more then one lens and thus changing would be cheaper and easier for multiple lenses. If you only had one lens you would want to convert the lens instead. Thus interchanging would be easy between mounts.
07-13-2011, 02:21 PM   #4
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What I actually wanted to know is why do I have hassle with a tool and put the adapter in the mount. The Y/C mount example proves that the adapter could be inserted like a lens if Pentax had designed K-mount differently. I have several third party adapters for K-mount, but the additional flange distance means that you can't focus to infinity, unlike with similarly simple Y/C to M42 adapter.

I thought there was a mechanical reason, but so far the reason seems to be marketing new K-mount lenses.

07-13-2011, 02:21 PM   #5
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QuoteOriginally posted by Jüri Quote
I have an old Yashica camera. It has a yashica/contax mount, so I have also aquired an M42 adapter. Using it is as easy as it could get. I just screw it on a M42 lens and get a y/c mount lens with infinity focus and no additonal glass. The adapter even pushes down that pin on automatic aperture lenses.

When I want to use M42 lenses with K-mount, I have to use a tool to insert a ring into the mount. The whole process is very inconvenient and takes time. And if i want to use the aperture on automatic M42 lenses, I need to disassemble the lens and find a way to fix the pin.

My question is why did Pentax make using M42 lenses on K-mount so difficult if it could be so much more convinient for many Pentax users.
Maybe I misunderstand you but:

1) Are you using the original Pentax K-bayonet-to-M42 converter? I don't need any special tools - a fingernail or a pencil is all that is needed, and

2) On genuine Ashai Pentax automatic Takumar M42 lenses, the pin controlling aperture will be depressed. Pentax cannot be made responsible for any and all M42 lenses of other brands that are out there.

In fact, as a long-time owner of various Pentax and Tamron Adaptall lenses I consider it a tremendous benefit of Pentax DSLR's that you have backwards compatibility all the way over their K-A and K-M to M42 Takumars. With Takumars and a genuine pentax adapter you also retain focus confirmation without needing any modifications, extra chips or whatsoever....
07-13-2011, 02:22 PM   #6
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Other than using the original Pentax K adapter, you can push the A/M switch to manual position (if there is a switch), so you'd be able to change aperture w/o pushing in the pin at the rear end. But unfortunately some M42 lenses don't have such as switch, then you can use an adapter w/ the capability of locking the pin in (yes, there are a few options out there).

I used to collect and use Takumar lenses. But because they are not as easy as using a K lens, so I've let them go and only using PK lenses now.
07-13-2011, 03:11 PM   #7
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QuoteOriginally posted by frank Quote
Other than using the original Pentax K adapter, you can push the A/M switch to manual position (if there is a switch), so you'd be able to change aperture w/o pushing in the pin at the rear end. But unfortunately some M42 lenses don't have such as switch, then you can use an adapter w/ the capability of locking the pin in (yes, there are a few options out there).

I used to collect and use Takumar lenses. But because they are not as easy as using a K lens, so I've let them go and only using PK lenses now.
Sorry, I correct myself - yes, you have to have a lens with an A/M switch and set that lens in the M-position. And that is what automatic Takumars do have. Again, Pentax cannot be made responsible for other brands and designs.

Thanks for the clarification.

Last edited by Stone G.; 07-13-2011 at 03:14 PM. Reason: missing word
07-13-2011, 03:21 PM   #8
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One of the reasons that I use Pentax is defenitely the backwards complatibility, which no other DSLR brand has. However, the fact is that with Pentax I have to put the whole adapter inside the mount, while Y/C system allows to add the adapter easily or even put it on a lens, while retaining infinity focus. I thought there might be a particular reason the K-mount system was not designed that well considering the M42 compatibility.

07-13-2011, 03:28 PM   #9
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As some above have mentioned with an official Pentax adapter using M42 lenses on a K mount DSLR isn't that hard at all. I actually like the screw mount lenses better than the K mount ones. I find the screw mount a lot less awkward to use than the K mount on either type of camera really. I can change out a screw mount lens on my SPII fairly quickly versus doing the same on my K mount SLR. It takes a bit longer on my K-x because of having to screw in the adapter first, but if I am switching M42 lenses out same deal so long as I leave the adapter in place. The Pentax version of the adapter comes out very easily I've found. I tend to fumble a lot more with swapping out K mount lenses myself.
07-13-2011, 03:37 PM   #10
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Just buy inexpensive infinity focus adapters, take off the spring, and leave the adapter on the lens. Voila! A K-Bayonet mount lens.

Hint: unscrew the little screw holding the spring clip to the adapter - discard the spring clip - screw the adapter to the lens - use the little screw in its original hole to secure the adapter to the lens.
07-13-2011, 07:12 PM - 1 Like   #11
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Try using M42 lenses on a Nikon.
07-13-2011, 07:24 PM   #12
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I think the OP does not have an Origonal adaptor and does not fully understand the use

You put the adaptor on the lens and then insert it no tool required. The adaptor stays in the body and makes it a screw mount body. To remove the adaptor takes a ball point pen or other similar object to release the holding tang. No tool necessary

There is also no loss of infinity focus

Loss of infinity focus is with third party adaptors not pentax ones. Tools come with third party adaptors not pentax ones
07-13-2011, 08:03 PM   #13
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Aside from having a flange for the aperture pin, using lenses on a Pentax is so much better than on a Canon...SR, open-aperture metering, and digital preview to name a few.

The original adapter is the only way to go. It's even better that Pentax specifically designed the K mount so screw mount lenses would continue to be usable. Amazing
07-13-2011, 08:46 PM   #14
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I find them to be easier to use than M and K lenses.
07-14-2011, 02:12 AM   #15
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QuoteOriginally posted by Jüri Quote
One of the reasons that I use Pentax is defenitely the backwards complatibility, which no other DSLR brand has. However, the fact is that with Pentax I have to put the whole adapter inside the mount, while Y/C system allows to add the adapter easily or even put it on a lens, while retaining infinity focus. I thought there might be a particular reason the K-mount system was not designed that well considering the M42 compatibility.
Have you actually tried putting the adapter on the lens first and then mounting it on the camera? Removing the adapter will require removing the lens first, but that's another story.

The big deal with adapting M42 to K mount is that they have the same registration distance, so the M42 adapter needs to fit inside the K mount. This in turn means that it cannot lock to the body using the K-mount lock pin, so it needs that small tab to lock inside the mount and that in turn means that you cannot remove the adapter without removing the lens first to gain access to the tab.

I'm not familiar with the Yashica mount, but their registration distance and lens locking mechanism are probably different. Why didn't Pentax change the registration distance? Probably to save cost on changing lens designs. Why didn't they come up with a different locking mechanism that could be used by the adapter as well? I have no idea. They could indeed have done a better job in this area, but maybe they wanted to push people to buy new lenses, so they didn't waste time to make the adapter story better.
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