Pentaxians... Any out there?

Fotodiox M645 to PK adapter dimension question

I also posted this on the Pentax forum, but many get an answer sooner here. I just got a Fotodiox M645 to Pentax PK adapter from B&H. They are back in stock after a long back order. Measuring it face to face I get about 17.26mm as the machined adapted distance from the longer Mamiya registration to the Pentax registration. The literature I have researched tells me it should be M645 63.30mm minus Pentax 45.46mm equals 17.84mm. I also have a Chinese made non branded version from another manufacturer that also measures 17.26mm +/- .03mm. I have a couple of M645 lenses I was anxious to use with my K5IIS and while I was waiting for delivery from China and for Fotodiox I made my own M645 to Pentax PK Adapter from a M645 no. 1 extension ring and a PK reversal ring using the 17.84mm dimension. It seemed to work fine and focuses on infinity, (or across the Bay), at the proper place with both my lenses. The Fotodiox and Chinese adapters seem to come into infinity focus just a bit early, but with my eyes it is hard to tell. Has anyone else noticed that the Fotodiox and Chinese manufactured adapters may be off a bit? My guess is that the Chinese adapters may have copied the Fotodiox adapter dimensionally, but who knows? I’d really like to know what is correct since I want to make another adapter for M645 to Pentax/Universal M42, and it technically uses the same 45.46 mm registration distance. I can understand a couple hundredths manufacturing difference, but not .5mm
 
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I have found the answer to my own question about adapter flange distances. It seems most manufactured adapters are intentionally made slightly short so they focus past infinity. This is to account for varying non standard lens and camera distances that could result in not focusing to infinity which is not good. Since I am making my own adapter I can be a bit more precise and use 17.84mm minus .03 plus nothing.
 
Disappointed_Horse said:
Just to be clear, the Super-Multi-Coated Takumar is the lens produced from 1971–72 (product code 37902). These have the scalloped metal focusing ring. "Super-Multi-Coated" is sometimes abbreviated "S-M-C."

"SMC Takumar" (no hyphens) is the name of the last version produced from 1972–75 with the rubberized focus ring (product code 37908) and open-aperture metering on the Spotmatic F, ES and ES II.

See SMC/S-M-C/Super Takumar 50mm F1.4 Reviews - M42 Screwmount Normal Primes - Pentax Lens Reviews & Lens Database.

As far as I know all of the seven-element 50mm f/1.4 Takumar lenses had the thorium coating (which I believe also carried over into at least the first K-mount 50mm f/1.4 SMC Pentax lens).

One thing I am confused about is when the open aperture metering feature was added to these lenses. My lens is an S-M-C Takumar, but has open-aperture metering. The Pentax forum page I linked above indicates that only the SMC lens had open aperture metering.
Click to expand...

The ones with the scalloped focusing ring are the lenses produced before 1972. They are called:
- Milticoated super-takumar
- or just Super - Takumar

If they cone from the pre-Spotmatic era and have a stop-down lever they are called Auto-Takumars

If they were made for the Spotmatic-F or ES-series, they have an extra pin on the back of the mount and they are called "Super-mulicoated Takumar". The 50mm lost its scalloped focusing ring and got a rubberized one but the rest of the Takumars kept it.

There is also a small batch of 55mm lenses that were produced at the end of the "Super-Takumar" era and the beginning of the "Super-multicoated Takumar" era. They have scalloped focusing ring but have the extra pin on the mount meaning that they can still be used on the later Spotmatic F or ES. I have one of those

IMG_20250329_164700_(525_x_700_pixel).jpg

IMG_20250329_164647_(800_x_600_pixel).jpg
 
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p.giannakis said:
The ones with the scalloped focusing ring are the lenses produced before 1972. They are called:
- Milticoated super-takumar
- or just Super - Takumar

If they cone from the pre-Spotmatic era and have a drop-down lever they are called Auto-Takumars

If they were made for the Spotmatic-F or ES-series, they have an extra pin on the back of the mount and they are called "Super-mulicoated Takumar". The 50mm lost its scalloped focusing ring and got a rubberized one but the rest of the Takumars kept it.

There is also a small batch of 55mm lenses that were produced at the end of the "Super-Takumar" era and the beginning of the "Super-multicoated Takumar" era. They have scalloped focusing ring but have the extra pin on the mount meaning that they can still be used on the later Spotmatic F or ES. I have one of those

View attachment 4859661

View attachment 4859662
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Dear P Gianakis,

I was under the impression that the square tab is the key to having a Takumar that offers full aperture metering on the F's and ES's. I never really paid attention to the extra pin.

Here are pictures of a 300mmf4 Super Takumar in the old M42 mount without the tab. I couldn't stand using it stopped down on my F's and ES but it works great with Canon EOS and even M4/3 with the proper adapters. Focus confirmation works on both brands courtesy of an m42 to EOS adapter with focus confirmation and a Viltrox EOS to M4/3 speed booster. A 560mm f2.8 is a nice thing to have on an M4/3 body!

Regards,

Tim Murphy

Harrisburg PA 🙂

IMG_20250329_133900_MP by Tim Murphy, on Flickr

IMG_20250329_133942_MP by Tim Murphy, on Flickr

IMG_20250329_134025_MP by Tim Murphy, on Flickr
 
Thanks Pan, I was wondering because I have a M/S 50/1.8 SX lens I use with a K5IIs and a M42 to PK adapter. I had to machine off an outer flange and remove the pin that communicates aperture to the M/SX body. It can get the lens stuck on the Pentax K body. You can see the hole where I pulled it out at the bottom rear of the lens. I also had to disable the auto aperture pin since the MSX lenses do not have a manual/auto switch. I thought about getting a Takumar for the K5 but didn’t want to run into the same problem, though I think Pentax made everything backwards compatible.

IMG_0727.jpeg
 
Tim Murphy said:
Dear P Gianakis,

I was under the impression that the square tab is the key to having a Takumar that offers full aperture metering on the F's and ES's. I never really paid attention to the extra pin.

Here are pictures of a 300mmf4 Super Takumar in the old M42 mount without the tab. I couldn't stand using it stopped down on my F's and ES but it works great with Canon EOS and even M4/3 with the proper adapters. Focus confirmation works on both brands courtesy of an m42 to EOS adapter with focus confirmation and a Viltrox EOS to M4/3 speed booster. A 560mm f2.8 is a nice thing to have on an M4/3 body!

Regards,

Tim Murphy

Harrisburg PA 🙂

IMG_20250329_133900_MP by Tim Murphy, on Flickr

IMG_20250329_133942_MP by Tim Murphy, on Flickr

IMG_20250329_134025_MP by Tim Murphy, on Flickr
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That is true, i edited the picture to point out which pins gets stuck in tge zenits but now it is confusing.
Super-takumar looks like the pic you posted.

IMG_20250329_181713_(600_x_800_pixel).jpg
 
p.giannakis said:
That is true, i edited the picture to point out which pins gets stuck in tge zenits but now it is confusing.
Super-takumar looks like the pic you posted.

View attachment 4859672
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Dear Pan,

Yes, I bought a working Mamiya 1000 DTL but after reading the cautions about some Pentax M42 mount lenses getting stuck on the body I took it to the local Goodwill Shop rather than deal with potential problems. I like my Pentax lenses, and I didn't want to risk doing damage to them.

Regards,

Tim Murphy

Harrisburg PA 🙂
 
oldhaven said:
Thanks Pan, I was wondering because I have a M/S 50/1.8 SX lens I use with a K5IIs and a M42 to PK adapter. I had to machine off an outer flange and remove the pin that communicates aperture to the M/SX body. It can get the lens stuck on the Pentax K body. You can see the hole where I pulled it out at the bottom rear of the lens. I also had to disable the auto aperture pin since the MSX lenses do not have a manual/auto switch. I thought about getting a Takumar for the K5 but didn’t want to run into the same problem, though I think Pentax made everything backwards compatible.

View attachment 4859671
Click to expand...
Aha, i see what you mean. Never heard of this issue before.

M42 mounts are constructed in different ways - compatibility can be an issue. Have a look at the picture below, they are so different.
IMG_20250329_182814_(900_x_572_pixel).jpg

And from what I see online, the mamiya is different too.

Screenshot_20250329-182649_Chrome.jpg
Edit: @Tim Murphy looks like the mamiya has the mount screws like the Zenit. They get stuck in there.
 
p.giannakis said:
The ones with the scalloped focusing ring are the lenses produced before 1972. They are called:
- Milticoated super-takumar
- or just Super - Takumar

If they cone from the pre-Spotmatic era and have a drop-down lever they are called Auto-Takumars

If they were made for the Spotmatic-F or ES-series, they have an extra pin on the back of the mount and they are called "Super-mulicoated Takumar". The 50mm lost its scalloped focusing ring and got a rubberized one but the rest of the Takumars kept it.

There is also a small batch of 55mm lenses that were produced at the end of the "Super-Takumar" era and the beginning of the "Super-multicoated Takumar" era. They have scalloped focusing ring but have the extra pin on the mount meaning that they can still be used on the later Spotmatic F or ES. I have one of those

View attachment 4859661

View attachment 4859662
Click to expand...
My 50mm f/1.4 Super-Multi-Coated Takumar has the scalloped focusing ring, which I much prefer. It has the extra pin. My 55mm f/1.8 Super-Multi-Coated Takumar is like yours, also with the scalloped ring.
 
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This is a M/S SX body. The offending pin is in the aperture ring on SX lenses and operates the tab in the slot you can see just outside the mounting ring. It causes seating problems on other M42 mounts and can also catch in them. That pin you show on the Takumar lens makes it bad for use on M/S cameras because of the 4 mount screws shown and the possibility of it catching in the recesses. The earlier TL and DTL M/S lenses are fine on most M42 cameras.

IMG_0729.jpeg
 
p.giannakis said:
Really? I haven't seen a 50f/1.4 like that. I only thought the 55s had a transition version. Can you post a pic with the s/n ?

Edit: I found it here: Review of Super-Multi-Coated TAKUMAR 1: 1.4 / 50 ASAHI OPT. CO., JAPAN | Happy
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Sure, here are a couple of quick iPhone snaps. No time to get out the DSLR and macro lens right now.

IMG_2607.JPGIMG_2605.JPG

This lens was a lucky garage sale find. I had Eric clean it up for me and it's a great performer. I'm particularly impressed with how well it performs with the close-up filter.
 
Thank you very much for the warning. Up to now I luckily never ran into such problem with Asahi S-M-C Takumar lenses at Praktica bodies.

But I met some issues in the other direction: On a Asahi Pentax Spotmatic F or ES II (those with open aperture metering) some foreign lenses are impossible to mount or even get stuck. For example, a Carl Zeiss Jena Flektogon 4/20 at Spotmatic F gets stuck. Can be solved by opening the shutter (B) and pushing the blocking pin while rotating the lens carefully. Not possible to solve without taking the film out.
 
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