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02-10-2016, 07:52 AM   #1
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Difference between M and K mount lenses?

The only thing I can find on the subject is that the K lenses are a little larger than the M variety? I've read the thread that supposedly explains it, but I'm even more confused now than before!


Just a simple question looking for a simple answer.... if there is such a thing.

02-10-2016, 08:04 AM   #2
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QuoteOriginally posted by Dewman Quote
The only thing I can find on the subject is that the K lenses are a little larger than the M variety? I've read the thread that supposedly explains it, but I'm even more confused now than before!


Just a simple question looking for a simple answer.... if there is such a thing.
Well for a usability point of view, there is none that I know of -- they operate the same. (And of course the "K" lenses weren't/aren't actually officially called that, they were just the first series of K-mounts.) The M line was just the next generation of designs, so just the normal incremental differences you'd expect. New optical designs, some different materials used maybe, improvements in coatings, etc. It would be interesting to see some marketing materials from the time to see what they were touting about the M line...
02-10-2016, 08:21 AM   #3
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I'm confused. The title asks about K and M mount lenses. K-mount is Pentax K mount, as all Pentax DSLRs have it (and in the past various film SLRs as well). M-mount usually refers to Leica M which is made for rangefinders and is, as far as I know, completely incompatible with Pentax K. More info on M mount here: https://en.wikipedia.org/wiki/Leica_M-mount

OR

Maybe you meant Pentax lenses which were called M series? These M series lenses are K-mount. They came after the previous series, which was not really officially labelled, but is commonly called K-series because it was the first K-mount series. All Pentax K and Pentax M lenses will fit on your Pentax cameras. You can see the index of lenses here: Pentax Lenses - Pentax Lens Reviews & Lens Database
m42 was the old screw mount, which was replaced by K-mount bayonet system, which started with K and later M and later A series. The series would evolve over time. For example, A series is the first with auto-aperture (where you can select aperture through camera instead of twisting the aperture ring by hand on the lens). F series was the first with autofocus, and so on. Each series also has its own style of appearance. M series is known for rather tiny, metal lenses. K series is known for slightly bigger lenses, but many had really great image quality. Note that some optical lens designs went through the series - for example M 50mm f1.7, A 50mm f1.7, F 50mm f1.7, FA 50mm f1.7 and DA 50mm f1.8 share this lineage - they have very similar, if not the same, optical design. But some lenses only made an appearance for a short time, within one series.

So I don't know what exactly the question was. Leica M mount lenses are completely different. I think the Pentax FA 43mm limited was also produced in Leica M mount for a while. But this is not really relevant unless you have a camera with Leica M mount
02-10-2016, 08:23 AM   #4
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the latter is his question... both K-mount lenses, but specifically the 'M' vs 'K' series of lenses....

02-10-2016, 08:24 AM   #5
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The M line of lenses were touted as smaller and more compact designs - intended to save the photographer the back-breaking weight of a full bag of Nikon equipment. There was a nice ad showing the Pentax MX and its lenses and motor-drive superimposed on the silhouette of what was obviously a Nikon F2 kit. Olympus did the same thing a few years earlier with their OM-1 being positioned as a lighter, smaller alternative to the bigger pro-SLRs.

But to go with the smaller MX, ME, ME-Super etc. Pentax needed a lineup of smaller lenses. Presumably more than a few needed optical re-designs to make them fit in the smaller barrels.

You might notice there was no such thing as a M version of the 50mm f1.2. It stayed as a K model, as there was no way they were going to make that any smaller!

The M lenses continued along until the need for an "A" setting on the aperture ring and electrical contacts to allow program and shutter priority modes on the Super Program (Super A).
02-10-2016, 08:30 AM   #6
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QuoteOriginally posted by pepperberry farm Quote
the latter is his question... both K-mount lenses, but specifically the 'M' vs 'K' series of lenses....
I thought so, but the title says something else. Better to explain everything just in case OP or some beginner reading this thread months later is confused.
Have to admit, this whole naming thing is fairly confusing, since various brands use a single letter. Like for the mount name, or for the camera name, lens series, and so on
02-10-2016, 08:46 AM   #7
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Were "K" lenses just the M-series lenses before the A-series came about, after which they needed a way to distinguish the M and A? Or was there a time before A-series where were lenses produced with the "Pentax-M" label?
02-10-2016, 08:52 AM   #8
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QuoteOriginally posted by disord3r Quote
Were "K" lenses just the M-series lenses before the A-series came about, after which they needed a way to distinguish the M and A? Or was there a time before A-series where were lenses produced with the "Pentax-M" label?
No. The "K Series" are labeled as SMC Pentax. Introduced in 1975. The M series were introduced starting a year later. They are smaller and some have new optical formulas. i.e. the K 50/1.4 has a 52mm filter ring, the M 50/1.4 has a 49mm filter ring. The M series are all labeled SMC Pentax-M.

There are some lenses in the K series that didn't make it to the M series. Besides the aforementioned 50/1.2 the 135/2.5 was never made in a M version. The 15/3.5, 18//3.5 and 17//4 FE didn't get M versions either. There were 34 different K primes and only 22 M primes...The M series zooms were much improved compared to the K zooms.

Pentax K-Mount Lenses Explained: The differences between various Pentax lens series


Last edited by boriscleto; 02-10-2016 at 09:00 AM.
02-10-2016, 09:06 AM   #9
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QuoteOriginally posted by disord3r Quote
Were "K" lenses just the M-series lenses before the A-series came about, after which they needed a way to distinguish the M and A? Or was there a time before A-series where were lenses produced with the "Pentax-M" label?
The so-called "K" lenses didn't have a series name on them -- they just say "SMC Pentax". I don't think anyone called them "K" in the way we call them that now until the Ms came out or possibly much later. (It could well be an invention of this web site?)

The M lenses do say "Pentax-M", yes. And all the rest follow: the A lenses say "Pentax-A", and the F say "Pentax-F", onto FA & DA...

The Ks and Ms get confused in the used market, however, so if you see a lens listed as M, make sure it really is (many think any manual non-A lens is a "M"), and if you see one as a "K" that often doesn't mean anything but K-mount as they aren't really called that, after all...
02-10-2016, 09:13 AM   #10
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Just to add: in terms of functions on a DSLR there is no difference between K and M series. Both can be mounted directly (no need of adapter), both require stop down metering with green button or Av mode which only shoots wide open; neither have AF, but they probably allow Catch in focus (aka focus trapping). This is because K and M series are not capable of communicating aperture to camera and were made before AF was invented. Pentax A and later series can communicate aperture to camera, so they allow full Av and P and other modes on modern Pentax DSLRs. But Pentax A still predates AF. F and later have auto aperture as well as AF.
02-10-2016, 09:17 AM   #11
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QuoteOriginally posted by boriscleto Quote
No. The "K Series" are labeled as SMC Pentax. Introduced in 1975. The M series were introduced starting a year later. They are smaller and some have new optical formulas. i.e. the K 50/1.4 has a 52mm filter ring, the M 50/1.4 has a 49mm filter ring. The M series are all labeled SMC Pentax-M.

There are some lenses in the K series that didn't make it to the M series. Besides the aforementioned 50/1.2 the 135/2.5 was never made in a M version. The 15/3.5, 18//3.5 and 17//4 FE didn't get M versions either. There were 34 different K primes and only 22 M primes...The M series zooms were much improved compared to the K zooms.

Pentax K-Mount Lenses Explained: The differences between various Pentax lens series



"The "K Series" are labeled as SMC Pentax. Introduced in 1975."

"The M series were introduced starting a year later. They are smaller and some have new optical formulas. i.e. the K 50/1.4 has a 52mm filter ring, the M 50/1.4 has a 49mm filter ring. The M series are all labeled SMC Pentax-M."

Thank you. THIS is the answer I was looking for! Now I know.


I suppose I SHOULD have asked, "What's the difference between "K" and "M" Pentax lenses.
02-10-2016, 09:43 AM   #12
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You may find this resource useful for ALL things K-mount:

Welcome to Bojidar Dimitrov's Pentax K-Mount Page
02-10-2016, 12:25 PM   #13
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The K Series was standardized on the 52mm filter thread and the M Series went back to 49mm, so the hoods and hard lens cases are not compatible.

Also most of the original K Series lenses released in June 1975 were based on Takumar optical designs.

The initial K Series had a slightly different styled "name", using the 50/1.2 as an example:

SMC PENTAX 1:1.2/50

then in 1977 the surviving K Series lenses used smc PENTAX 1:1.2 50mm

Phil.
02-10-2016, 03:16 PM   #14
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QuoteOriginally posted by pepperberry farm Quote
the latter is his question... both K-mount lenses, but specifically the 'M' vs 'K' series of lenses....
Yes -- the use of "mount" after "K" (instead of "series" or "line" or something such) was unfortunate. Terminology matters.
02-10-2016, 03:20 PM   #15
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QuoteOriginally posted by fwcetus Quote
Yes -- the use of "mount" after "K" (instead of "series" or "line" or something such) was unfortunate. Terminology matters.


agreed...
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