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12-28-2013, 11:01 AM   #1
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Experience with Mamyia Sekor SX/CS M42 mount ?

Hi,
I have a question regarding the Auto Mamiya Sekor SX 21mm F4 in modified M42 mount and/or the Auto Mamiya-Sekor CS 21mm F2.8.

There is some info on the net, but not conclusive, regarding the modified M42 mount. I read many Pentax users have problems with a pin and/or the edge of the Mamiya mount. The pin transmits the aperture information to the body and could prevent mounting the lens on adapters. I am not willing to do major surgery on the lens if I buy it.
On the other hand, I saw a few Pentax (standard) M42 adapter users with no problem at all with this lens.


I hoped this adapter would do the trick, but the seller said in probably wouldn't...


Anyone experience with this lens on a Pentax camera?


RemcoR

12-28-2013, 11:09 AM   #2
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The Vivitar TX adapter is for Vivitar TX lenses to put them on a Mamiya body. So forget about that.

Yes, Mamiya/Sekor m42 lenses do need at least one modification, and possibly two to mount properly on a Pentax camera with an adapter. The aperture ring overhangs the base of the mount, and it needs to be flush. (I think they are all like this -- but some early ones might not be -- all of the SX ones I've seen are.) So the entire edge of the ring needs to be filed down. Second, SOME of them have a hard pin in the mount. This is worse than the Ricoh pin -- it is a hard, nasty, pokey little pin like a nail sticking out. It must be removed if it is there, but it isn't always there.

If you use a non-infinity m42 adapter, you might get away with not filing down the aperture ring (and you might not), but then you lose infinity.
12-28-2013, 11:46 AM   #3
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QuoteOriginally posted by vonBaloney Quote
(I think they are all like this -- but some early ones might not be -- all of the SX ones I've seen are.)
Nope. They are not all that way.

My understanding of the Mamiya/Sekor compatibility is:
  • SX lenses have an interfering pin* and most (all?) have the overhanging aperture ring. A/M switch is not present that I am aware of.
  • Auto Mamiya/Sekor are standard M42 with an A/M switch. An overhanging aperture ring would not surprise me on some models, but I don't know that to be a generic issue with the brand
  • To the best of my knowledge, there is no CS (NC bayonet) to Pentax-K adapter


Steve

* The pin and a locking slot are the signature features of the SX series. The combination allows for open-aperture metering with the Mamiya/Sekor MSX and DSX camera bodies.

Last edited by stevebrot; 12-28-2013 at 12:02 PM.
12-28-2013, 11:58 AM   #4
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Thank you both.

You confirmed my suspicions with this lens. I hoped to have found a cheap but very good alternative to a couple of very expensive lenses. There are a few comparisons with highly regarded ones like the Leica and the almighty Carl Zeiss Distagon T* 21mm f2.8, as can be seen Leica R21 f4 vs ZF 21mm f2.8 vs ROLLEI MC 21mm f4 ?? | Chan'Blog ???????????????????????????. The Mamiya (same lens as the Rollei) comes out very nicely in this test. Oh well keep on searching ....

RemcoR

12-28-2013, 12:00 PM   #5
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Oh yeah, forgot that you have to glue the aperture pin down too!

I have a 135/2.8 with the overhanging ring, but no pin. It is not marked SX but seems identical to the one that is. (Which I used to have.) I think the 21mm does have the overhanging ring, if memory serves, although I have never had that one myself. I've ended up filing down three of them now, with this 135mm waiting in the wings. (I regretted selling the last one, just waiting until I get a new dremel tool so I can do a cleaner job.)
12-28-2013, 12:50 PM   #6
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Of course it depends on what you place most emphasis on; however, you may want to look at the Vivitar/Soligar 21mm f3.8 (T4) lens. It has essentially no distortion (as discussed in the attached post/or one of his other posts on this lens) and I concur. In numerous theatre photos (to show the entire set) I never noticed any distortion.

It is my second most used lens; however, I place less emphasis on resolution--and It does not have great resolution--but I find it fine for 8"x12" (I use it at f/5.6 due to low theatre lighting).

You do need to open the T4-M42 adapter and wedge the A/M switch into M--to force into fully manual mode. Pretty simple as described in the following (BTW I tried M42 adapters that have a "shelf" to hold the lens in M mode--but it was slightly oversize [plating?] and unusable--and I only use the official Pentax K adapter).

gabriel.mp3-tech.org/blog/index.php?entry=entry090320-154132
12-28-2013, 04:35 PM   #7
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As far as I can figure out, the Mamiya/Sekor TL Series had the classic and usable M42 mount without the pin and edge: Mamiya TL and DTL 35mm Cameras
Unfortunately, this series did not have the wide angle 21mm I am after. The TL and DTL series started with a 28mm: Mamiya 35mm SLR Lens Auction Prices
The 21mm only started in the SX series with the modified M42 mount that requires a lot of dremel skills.

I have a few alternativesI am looking at, like the Olympus OM 21mm F2 but that lens has a few drawbacks, like hefty fignetting and soft corners under F4. There is also the Carl Zeiss 18mm F4 (contax mount I can modify with the Leitax adapter), or perhaps I should be content with the excellent Carl Zeiss Distagon 28mm F2/2.8. I would like however something wider like 18-21mm (also with a future FF Pentax).

Thanks again for your input on this quest.

RemcoR
12-28-2013, 04:55 PM   #8
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Other (old) wide-angles:

Tamron Adaptall 17mm (get a PK or PKA adapter)
Vivitar 19/3.8 (available in PKA mount)
Tokina 17/3.5 (PK mount, somewhat hard to find)
There is a non-T4 Vivitar 21mm out there too I think,

12-28-2013, 08:33 PM   #9
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If it helps I would mention my experience. I went though a period looking for another wide lens. As I said I like the Vivitar 21mm T4 (I think I paid $100 for it w/ M42 adapter), but I would like something with higher resolution and still very low distortion, and not willing to go over $200 about. And I purchased:

-- Tamron 17mm [I like the adaptall 2 SP lenses**] but it was mechanically defective--in any event I am interested in lower distortion
-- Pentax PKA 20mm f2.8 in UG condition from KEH: hoping it was mechanically UG, but it was optically UG (otherwise this lens is too costly)
-- .Finally settled on a SMC Takumar 24mm f3.5--as it is sharp and low in distortion

Again my main interest is low distortion. That may not be important to you, and if not the more recent of the two 17mm tamrons (51BB) seemed to me to be the best/easily obtainable option. If you do get this I used a step up or step down ring (forgot which) that exactly fits inside the lens (I held it in w/ photo tape as It was on the lens I returned) and mounted the Pentax Takumar 24mm f/3.5 metal hood. This was a nice setup--as long as you are on the cropped sensor.
__
** 350mm SP mirror and 35-80mm SP macro. On the other hand my copy of the 24mm f2.5 non SP lens was optically unusable.
12-28-2013, 08:41 PM   #10
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There is also a 20mm f/2.8 spiratone, promaster (?), ... that Hinman spoke well of. But It seems that is also very hard to find.
12-29-2013, 04:02 AM   #11
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Hello guys,

The reason for getting a wide angle lens is for landscapes, so distortion is not a major concern. I currently use the old version of the Sigma 17-70 f2.8-4.5 for it, but it has weak corners and I get a sort of smeared /lack of sharpness effect with objects like mountains, like here: https://picasaweb.google.com/lh/photo/6OfW1yt1oqoeXDE83ghKM9MTjNZETYmyPJy0li...full-exif=true

I am in the process of upgrading my lens lineup and so far ended up with two MF lenses: the Pentax A 35-105 F3.5 (stack of primes) and the Carl Zeiss Planar T* 50mm F1.7, both around $ 100. I am extremely pleased with both. The sharpness of both is stunning: https://picasaweb.google.com/RemcoRog/CarlZeissPlanarT50MmF17. Only thing lacking now is this quality (for this price) in the wide end.

For this I could go for a AF/APS-C lens on my current K-5, but I am hooked on MF and would like to be able to use it on a future FF Pentax. I have seen some of the lenses you mentioned and will look at them further. The CZ flektogon 20/2.8 was less sharp compared to my current Sigma.

RemcoR
12-29-2013, 04:23 AM   #12
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Hi Remcor
Have a look for a 20/3.5 Zeiss Flektogon with an M42 mount. This is a well known good performer with low distortion and no problems mounting on Pentax DSLRs. also have a look for an RMC Tokina 17 3.5 in K mount, another good performer. Not perfect by any means in terms of distortion but better than many zooms and very easy to use with a native k mount. Good to see that you use a manual lens for landscape as AF is not needed for this genre and I believe in many cases a hindrance. Good luck
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