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02-04-2010, 12:00 PM   #1
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Does this kind of adapter exist?

I recently bought a cheap M42 to K-mount adapter on eBay. Mounted once, found to absolute rubbish and thrown in the bin.

I'd like an adapter that mounts (semi)permanently to the screw mount on the lens. It should click into place like a regular K-mount, lens so I can use the lens-release button on the K-7 when I take it off. Does this kind of adapter exist?

If not, does anyone know how to mod an adapter to fit my specifications?


Last edited by Flanker; 02-04-2010 at 12:01 PM. Reason: Grammmar
02-04-2010, 12:26 PM   #2
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No it doesn't exist. You can use the original Pentax adapter, remove it's spring lock, and screw and glue the adapter onto your M42 lens. Then drill a hole in the M42 lens mount plate (if it is wide enough, most aren't) to match the K mount locking pin.

Note, the original Pentax adapter mounts flush with the camera's lens mount flange. Some adapters are not flush and will not permit focus to infinity.

http://www.mosphotos.com/PentaxScrewmountLensAdapter.html

Last edited by Ole; 02-04-2010 at 12:31 PM.
02-04-2010, 01:17 PM   #3
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unfortunately, this type of adaptorrequires a flange to engage the locking pin,
there are flanged K mount adaptors but there are some problems with this adaptor.
it is 0.8 mm thick which upsets infinity focus.
you can attach true K mount adaptors, but there is no locking hole on the lens base. Some people modify the lens by drilling a hole in the lens base but I dislike that idea, Some lenses also are not wide enough at the base, for example my smc tak 35mm F2 to engage the locking pin.
What I cannot answer is whether it is possible to re-adjust the infinity focus to accept a 0.8mm thick flanged adaptor. I know this is possible on some vivitar / Kiron lenses but I do not know the individual designs well enough to make a general comment.
02-04-2010, 07:05 PM   #4
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It actually does exist but it won't allow you to get infinity focus since it is the "flange" type of M-42 adapter.
The hole that engages the locking pin is on the flange adapter.
It doesn't allow focus to infinity because it adds a millimeter or two to the distance of the lens to the sensor plane.
Here is an example of it:

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02-05-2010, 08:43 AM   #5
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I did precisely what you want with a Takumar 17mm fisheye lens.
I took a pentax M42-K adaptor and removed the spring. I then put the adaptor onto the lens and, using the screw that was supposed to hold the spring in place, I jammed the adaptor to the lens.
A little careful measuring and a bit of work with a Dremel tool to put a small notch in the lens mount for the lock pin to engage, and I now have a Super Takumar 17mm fisheye in K mount.
A lot of M42 lenses won't allow this because they are enough smaller than the K mount that you can't get the pin to engage.
02-05-2010, 09:30 AM   #6
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If you would rather not put a notch in your M42 lens to stop it in the right place, you can do almost as well by filing the adapter so the roots of its ears are square as shown:

The square root will keep the lens from over-rotating when you mount it. The squareness of the root is the only meaningful difference I can find between an OEM adapter and third party adapter.

Dave

PS I use a notch when possible. Also, If you notch your type K lenses about 10 degrees early, you can use them in preset mode.
02-05-2010, 01:05 PM   #7
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QuoteOriginally posted by Wheatfield Quote
I did precisely what you want with a Takumar 17mm fisheye lens.
I took a pentax M42-K adaptor and removed the spring. I then put the adaptor onto the lens and, using the screw that was supposed to hold the spring in place, I jammed the adaptor to the lens.
A little careful measuring and a bit of work with a Dremel tool to put a small notch in the lens mount for the lock pin to engage, and I now have a Super Takumar 17mm fisheye in K mount.
A lot of M42 lenses won't allow this because they are enough smaller than the K mount that you can't get the pin to engage.

I did the same thing with my third-party adapter (the kind that allows infinity focus). I removed the spring and I have it mounted on the only M42 lens I use with my K10D, my old Super Takumar 50mm, f/1.4 from my Spotmatic.

I didn't bother notching or drilling the lens for the locking pin. I have found that friction is more than enough to keep the lens in place. I never had a problem with the lens falling off my Spotmatic and it doesn't come loose in the adapter. Nor does the adapter seem prone to falling off the camera.

I put the adapter on the lens as tightly as I could. With the combo off the camera, I held the lens in one hand and used the flat side of a screwdriver in the other hand to screw the adapter onto the lens. I can still get it off, if I need to, but it doesn't loosen when I dismount the lens-adapter combo from the camera.
02-05-2010, 01:38 PM   #8
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I have several M42 lenses converted to K-mount with the Pentax adapter, jut like several other here noted (unscrewed the locking spring and leave it permanently attached to the lens). On the lenses I converted there was plenty space to mill a notch in the M42 flange for the lock pin of the camera. It is the (for me) most convenient way to use M42 lenses.

Ben

02-05-2010, 05:18 PM   #9
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QuoteOriginally posted by Ben_Edict Quote
I have several M42 lenses converted to K-mount with the Pentax adapter, jut like several other here noted (unscrewed the locking spring and leave it permanently attached to the lens). On the lenses I converted there was plenty space to mill a notch in the M42 flange for the lock pin of the camera. It is the (for me) most convenient way to use M42 lenses.

Ben
Exactly what I did too with a Helios 44M but with the Industar 50-2, I had to use the flange type as the lens was too small for the body and if an M-42 adapter was used like the OEM type (with focus infinity), all the camera body electrical contacts are exposed.
02-06-2010, 09:52 AM   #10
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Thanks for alle the feedback on this. I'll have to experiment a bit here to find out what works for me.
02-06-2010, 12:43 PM   #11
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I don't have a problem with someone modifying a common lens like a Super Tak 55mm f1.8. But it would really disappoint me to encounter one of these that someone had fubar.

Takumar 100mm f3.5 Preset (1957) 1 on Flickr - Photo Sharing!

That link is to CheekyGeek's lens.
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