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12-12-2012, 10:47 AM   #1
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Pentax Spotmatic F with Mamiya M42 lens?

Hi everyone!
My first post in this forum will be the question if my two Mamiya/Sekor SX lenses (55mm/1,8 & 135mm/2,8) will fit and work as should on a beautiful Ashai Pentax Spotmatic SPF?
The Lenses has got the M42 mount and I've read on the web that they should fit the Pentax screw mount cameras... BUT, the Spotmatic F seem to differ from the others. I've found the following facts:
The Pentax Spotmatic SPF added full-aperture metering to all of the features found in the Spotmatic II. Full aperture metering required the newer Super-Multi-Coated (S-M-C) Takumar lenses with an aperture-position linkage to the camera.

The Mamiya lenses is the same as this one:
Mamiya/sekor 135mm 2.8 strange mount ?: Pentax SLR Talk Forum: Connect

And the answer to the thread above may hold the answer to my question (but I'm not sure if I understand it correctly):
Re: Mamiya/sekor 135mm 2.8 strange mount ?: Pentax SLR Talk Forum: Connect

Does that mean the lenses will fit the Pentax?
Anyone know if this will work or have experience of trying?


Thanks!
Regards

Jonas

12-12-2012, 12:17 PM   #2
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As long as it's M42 the lens should mount just fine and be usable, but you won't be able to leverage the open-aperture metering feature.

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12-12-2012, 01:04 PM   #3
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Actually, the SX series won't work -- the aperture ring overhangs preventing a flush mount and would need to be filed down. Some of them also have a nasty pin that need to be removed.
12-12-2012, 01:28 PM   #4
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Ok, have to admit that I'm not sure of what open-aperture and stop down metering really means (not much wiser after google'ing a bit)
What is open-aperure metering?
How do I perform the stop down metering on the Spotmatic F?

On the back of the Mamiya lenses is a small pin that moves with the aperture ring - I thought that pin was "talking" to the camera and providing open aperture metering?

Confused

12-12-2012, 01:31 PM   #5
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@vonBaloney - didn't see your answer before posting... that sucks ;(

thanks.
12-12-2012, 01:41 PM   #6
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QuoteOriginally posted by minimodi Quote
On the back of the Mamiya lenses is a small pin that moves with the aperture ring - I thought that pin was "talking" to the camera and providing open aperture metering?
I wasn't talking about the aperture pin -- on SOME of the Mamiya lenses there is another tiny hard pin that can cause problems. Whether if you filed down the ring the normal open-aperture metering would work on a Spotmatic I have no idea -- I've only used them on modern cameras with adapters where the pin is not used in that way. If you want to do the work and do mind messing them up a bit, filing down the ring so it will mount flush is worth the effort (and removing that that other pin if present, which it is in that picture in the link you provided) -- those are fine lenses -- the 135mm is very nice indeed. I've modified several M/S lenses so I could use them.

Almost any other m42 lens should be usable, and most with an auto aperture pin should allow open aperture metering -- the other exceptions that I know of that might give problems would be some Fujinon lenses and some Helios lenses. And Yashinon DX lenses will mount, but may hit the mirror at infinity because they extend too far (the 50/1.7 and 50/1.4). But any Takumars will obviously work (very early models may not allow open aperture metering, but all the Super Taks and SMC Taks will), as well as old m42 Vivitars, Rikenons, Focal, Sears, Tamron, Sigma etc etc.

Last edited by vonBaloney; 12-12-2012 at 01:46 PM.
12-13-2012, 04:56 AM   #7
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The lens mounting plate of the SPF has a recess around the opening that allows a small pin on later Tacumars to fall into. This lock the lens into "auto", which in turn facilitates metering with the lens in the open position. The SP11 and earlier Spotmatics don't do this.
12-13-2012, 11:03 AM   #8
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QuoteOriginally posted by arnold Quote
The lens mounting plate of the SPF has a recess around the opening that allows a small pin on later Tacumars to fall into. This lock the lens into "auto", which in turn facilitates metering with the lens in the open position. The SP11 and earlier Spotmatics don't do this.
Right, which is actually a little button to unlock the "auto-man" switch. But on the Mamiya/Sekor lenses with the extra pin, it is just a hard unmoving pin from what I remember (and there is no auto-man switch) -- some sort of locking pin. I don't know if it will cause trouble on a screw mount body beyond possibly causing it to not mount properly or maybe scratching the mount a bit, but if using it on a K-mount with a m42 adapter (the genuine type that mounts flush) it will cause the lens to get stuck and also run roughshod over your contact pins -- much like the dreaded "Ricoh pin".

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