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09-25-2011, 03:15 PM   #1
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What is a bare PK mount called?

I posted this in a response buried in another thread; thought I'd make it more visible.

I have a peeve or quandary or whatever, about Pentax bayonet mount nomenclature. Pentax introduced the mount with the K1000 in 1975. [See the Wikipedia entry.] The original K-mount, which is the same on M-type lenses, has the bayonet blades and a mechanical aperture-link lever. That's the native PK mount. The KA mount adds aperture-control pins; later F-, FA- and DA-mounts include autofocus. No problem.

But there's an even simpler mount, which lacks the aperture linkage. Just 3 bayonet blades and nothing else. This is what I find on T- and T2-mount adapters, some Adaptalls, mount-reversal adapters, cheap macro tubes and bayonets, wide-flanged M42-PK and M39-PK adapters, mirrors, etc. I've called this a bare-K-type mount. But that's not good enough. WHAT IS THE NAME OF A BARE K MOUNT? I am like so perplexed.

Non-AF mount variants:

PKM - K- and M-type lenses
PKA - A-type lenses
PKR - Ricoh-pin A-types

PK0 - zero-type lenses?

09-25-2011, 03:19 PM   #2
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Just K

then there is KA, KAF, KAF2, KAF3, and KF (me f lens, which nobody ever talks about)

None of the others are official specs AFAIK.
Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

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09-25-2011, 03:22 PM   #3
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Generic Bayonet Mount




...
09-25-2011, 03:30 PM   #4
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I like PK0 if you can make everyone use that. It would be better if it was immediately obvious that it should be read "PK Zero", not "PK Oh".

A couple of Pentax lenses have this kind of mount. One example is the SMC Pentax 500mm f4.5. I assume the aperture blades are just too far into the lens (possibly as much as a foot from the mount) for a good mechanism.

09-25-2011, 03:30 PM   #5
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QuoteOriginally posted by Adam Quote
Just K
But K- and M-series both have mechanical aperture linkage, which the 'bare' mounts lack. Calling the bare guy a K-mount confuses it with K-series lenses.

Thanks for the article, but it is wrong or at least misleading about aperture control. The author list K- and M-mount lenses as not being auto-aperture, when instead they are mechanical-auto, not electrical-auto. I'd also say that the article is about official camera mounts, not real-world lens mounts.

Sorry, this is a messy and illogical mount-naming system.

QuoteOriginally posted by joe.penn Quote
Generic Bayonet Mount
GBM -- isn't that Great Britain Monarchy?

EDIT:

QuoteOriginally posted by Just1MoreDave Quote
I like PK0 if you can make everyone use that. It would be better if it was immediately obvious that it should be read "PK Zero", not "PK Oh".
Or maybe:

PKL -- linkless
PKB -- bare
PKG -- generic
PKC -- cheap
PKZ -- zilch

Last edited by RioRico; 09-25-2011 at 03:39 PM.
09-25-2011, 03:44 PM   #6
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QuoteOriginally posted by RioRico Quote
...

Sorry, this is a messy and illogical mount-naming system.

...
Yes it is indeed messy and illogical. We users can't do anything about it I'm afraid. Pentax defined the nomenclature and it is cast in concrete by now.

It also doesn't help that the aperture simulator in the body was dropped at some point without changing the name of the mount. So a KAF2 camera body mount may or may not have an aperture simulator.

The other confusion is auto-aperture, what does that mean? In the Takumar days it meant that the camera can stop down the lens. Later, with the A-series lenses, we think of it as meaning that the camera can set the aperture.

Pentax produced bellows and extension tubes without the aperture stop-down lever. These were still called K-mount by Pentax.

Last edited by Ole; 09-25-2011 at 03:50 PM.
09-25-2011, 04:38 PM   #7
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The issue isnthat the meaning of auto aperture has changed over time

When SLRs began the aperture had to be stopped down manually because the camera had no means to do it.

Then automatic aperture began, which allowed for automatic stop down by the cam a, so focusing could be done wide open,

Ten camera makers added aperture setting linkages to allow for open aperture metering

Much later, they added electrical contacts, so the camera knew both v minimum and maximum aperture and also modified the linkage for aperture control to allow the camera to control not just stopping down the lens, but how far it stopped down,

Then, the aperture linkage and ring disappeared because they were redundant, and no camera newer than 30 years old needed them
09-26-2011, 11:45 PM   #8
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The pentax K28/3.5 shift has this mount too, PK Zero. I like this name ;-)

09-27-2011, 01:09 AM   #9
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Hmmmm, I do not fully agree.

First of all, there are two different mounts:

one on the camera body side, one on the lens or attachment side. The K mount on the (before MZ-50 and so on) camera body has always had the technical parts for open-aperture mounting and metering, even if the lens does not have this (like a mirror lens with fixed aperture).

So, if Pentax decided to call the mount with aperture lever only a K mount upon what the camera has, you'll find that on bodies beginning with K2 and ending with ME Super. The lens mount variations maybe were not taken into consideration for defining the mount and its name. There is no K mount camera body without the lug for open aperture metering and aperture lever and it seems to be named after the camera mount, not the lens mount.

Secondly, the difference in K (inofficial name) and M lenses talks about size and optical schemes and outer design, the mount and its variations (open aperture vs stop down) is the very same. The first real addition to the mount on the camera side came with the ME F (Kf mount) for autofocussing the 35-70 AF lens and a little bit after this the A pins for the aperture control via the camera.

Finally, the K2 was the first K mount model (along with KX and KM), the K1000 came after these three pioneers.

Pentax, alas, dealt with the lens-sided variations of the early K mount simply by telling: if you are using this lens or that accesory, you must use stop down metering.

And yes, you are right, there are K mounts on the lens side without anything except the three flanges, but I've never encountered a situation where I needed a name for it, "stop down metering only" did the job :-)

Just my 2 cts.
09-27-2011, 08:15 AM   #10
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QuoteOriginally posted by Vranx Quote
First of all, there are two different mounts:
Yes, and as you mention, Pentax officially defines the camera-side mounts, because they make/made the cameras; but doesn't officially define the lens-side mounts, because other fabricators get into the act.

QuoteQuote:
And yes, you are right, there are K mounts on the lens side without anything except the three flanges, but I've never encountered a situation where I needed a name for it, "stop down metering only" did the job :-)
I find a 'need' (or obsessive-compulsive desire) because, not counting a few that I hope to sell, I now have 55 lenses with some variety of K mount. I try to track these in my gear spreadsheet-database. I use KS (for Simple) for non-auto simple-mount lenses, and add a '#' for those I've adapted one way or another.

So I can apply my own tags, and *I* know what they mean -- but without an accepted naming convention, I must use clumsy language to communicate about them. I'd raised this question in hopes that maybe there exists some convention I didn't know of. Apparently not. Oh bother...
09-27-2011, 03:26 PM   #11
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you may need to name OM mount (or Nikkor etc) dremel'ed to fit K mount too
K-OM ? K-N ? ;-)
09-27-2011, 04:07 PM   #12
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QuoteOriginally posted by RioRico Quote
GBM -- isn't that Great Britain Monarchy?
Not in the '(recently?) civilized' world.

H2
09-27-2011, 04:24 PM   #13
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QuoteOriginally posted by hoanpham Quote
you may need to name OM mount (or Nikkor etc) dremel'ed to fit K mount too
K-OM ? K-N ? ;-)
No, much easier: OM#, NI#, C/Y#, etc.

One of these days I'll work up the courage to pull the base from my Minolta MC Tele Rokkor-PF 100/2.5 and replace it with a PK-M42 adapter. Then it'll be a KS# because it'll no longer have the MC/MD base. The perspective-control Schneider PC-Cinelux 60/2.8 that I glued PK macro tubes onto, that's a KS# also. But with NI & OM & C/Y & Exakta-mount lenses, I haven't replaced the base, just chopped them a little -- and except for the chopped Nikons, they can still be used on their host systems. So they get no K tag, just the #.
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