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02-18-2012, 11:41 PM   #1
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K Prime vs. M Prime

I own a few M prime lenses and I was wondering what the difference is between the SMC Pentax K prime range and the M prime range?

02-18-2012, 11:44 PM   #2
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K lenses are bigger (literally, that's it).

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

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02-19-2012, 12:00 AM   #3
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Also the K Series lenses tend to be better built and generally have better optics. Pentax went for small with the M Series primes and sacrificed optics for the M replacement of a K Series lens. The K Series lenses will cost more than the M versions.

Phil.

Last edited by gofour3; 02-19-2012 at 12:22 AM.
02-19-2012, 12:25 AM   #4
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The only difference between my M200/4 and my K200/4 is the size and lack of a built in hood on the K.

No difference in IQ whatsoever imo

02-19-2012, 12:40 AM   #5
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QuoteOriginally posted by JimD Quote
The only difference between my M200/4 and my K200/4 is the size and lack of a built in hood on the K.

No difference in IQ whatsoever imo
Similarly I briefly had a K28/3.5 and now have the M28/3.5. I don't believe the M is inferior, or if it is I couldn't see the difference.
02-19-2012, 03:27 AM   #6
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The main reason to consider the K lenses as better built than the M lenses is IMO the extra grip they have for handling when mounting them on a body. It makes the process easier. They are the ones I prefer. You can see the grip on the front lens (K 30) and not on the rear one (M 28). Otherwise, both series are all metal and glass. The plastic rings came latter, on the A lenses, in various combinations.
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02-19-2012, 03:43 AM   #7
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I don't see any difference in build quality between my K24/2.8
and its M20/4, M50/1.4, M100/2.8, or M200/4 stablemates.
All were listed together in Pentax literature of the early 'eighties.
The K24/2.8 is lighter than all my M's, except the M20/4.
02-19-2012, 04:12 AM   #8
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The differences really are size and weight. Also many of the fastest lenses disappeared in the m series. Gone are 50/1.2, 135/2.5, 200/2.5 and 500/4.5. The 85 went from F1.8 to F2. But the 300/4 and 400/5.6 got a lot smaller. The other thing is the feel. The K series for the most part feel better. Sorry I can't explain it differently. BTW I have K50/1.4, 105/2.8, 135/2.5 and300/4, and M28/2.8, 35/2, 50/1.7, 100/4, and 135/3.5 so I think I can make my comments objectively

02-19-2012, 06:40 AM   #9
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I find the K lenses often have a warm color cast, compared to the more neutral M lenses. The Ks tend to have more strongly damped focus rings. I like both series.
02-19-2012, 06:45 AM   #10
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QuoteOriginally posted by Lowell Goudge Quote
The differences really are size and weight.
Yep


QuoteQuote:
The other thing is the feel. The K series for the most part feel better.
I don't totally agree with this. I wouldn't say the K lenses feel better. They're just different. But they're close enough that I had to stop and think which of my lenses are Ks and which are Ms. (Edited to add) They're certainly close enough that, if I were the OP and had some M lenses, I wouldn't bother replacing them with Ks unless I got a deal I just couldn't refuse. And even then, it would depend on the lens.
02-19-2012, 09:46 AM   #11
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QuoteOriginally posted by gofour3 Quote
Pentax went for small with the M Series primes and sacrificed optics for the M replacement of a K Series lens.
While I do agree that M series primes tend to be (slightly) inferior, I'm inclined to doubt the optics were "sacrificed" because Pentax went small hypothesis. I suspect it had more to do with how quickly the M series was introduced. Every M series lens is a new design, and these lenses were introduced only two years after the K series. It was a rush job, and it sometimes shows. Two of the three M series lens that were introduced a few years after most of the M's were released, the M 28/2 and the M 300/4, were not rushed and these are two of the very best lenses in the series.
02-19-2012, 11:54 AM   #12
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There are some greats and some lemons in both series......you need to compare specific lenses to see difference. Though I generally prefer K series, some of Ms caught my attention: M35/1.4 (rare as hens teeth), M28/2, M85/2, M*300/4 (i had this one and it is great star lens)
Some of K's are basically SMC Takumar designs in K-mount....
02-19-2012, 12:08 PM   #13
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QuoteOriginally posted by vrrattko Quote
There are some greats and some lemons in both series......you need to compare specific lenses to see difference. Though I generally prefer K series, some of Ms caught my attention: M35/1.4 (rare as hens teeth), M28/2, M85/2, M*300/4 (i had this one and it is great star lens)
Some of K's are basically SMC Takumar designs in K-mount....
That M35/1.4 is on everyone’s wish list; unfortunately it never went into production. It’s basically a 35mm FL version of the K28/2 and features the same floating lens elements. That’s what made the K28/2 an all-time Pentax legend. The floating lens elements were dropped when the M28/2 came out, to reduce the size and cost of the M lens. While the M28/2 may be a great lens, it’s not is the same league as the K28/2 optically.

Phil.

Last edited by gofour3; 02-19-2012 at 04:57 PM.
02-19-2012, 12:31 PM   #14
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If I may I’ll chime in with an opinion on the “feel” debate K vs. M series. I have several lenses from each series and I would agree the K series generally do “feel” better than the Ms. As baron-ite said earlier they (K series) tend to be more strongly damped than the M series. The knurled grip found on the K series also makes them slightly easier to mount on your camera. I think it is safe to say if you have big hands you will probably prefer the “feel” of the K series. Like many above I think the K series are better built with more metal and a little more attention to detail such as the grip feature.

This is not to say the M series are bad. Quite the contrary they are very well made. Compare the build quality of a manual focus M series lens to the cheap plastic found in many modern lenses and you will see what I mean. My Pentax M 35/2 is the smoothest focusing of the many lenses I own. The Ms also have a colour cast which is quite distinctive. The M series renders the sky a bluish colour which is quite different than the K series. It is a Robin’s egg sort of blue I generally prefer to K series rendering. This is no doubt due to changing versions of the SMC coatings over the years.

Are the K series lenses sharper than the M series? Perhaps – but I would generally be hard pressed to tell the difference between the two series. I think it may be fair to say within certain focal lengths some K series lenses are sharper. In my experience the K 200/2.5 is much sharper than my M 200/4. This shouldn’t be surprising as the K 200/2.5 was and remains a far more expensive lens than its M series counterpart. As 200mm is the only focal length where I have a lens from each series, it is the only example I feel I can say with confidence that the K series lens is sharper.

At the time of writing I have most of the lenses from each series I really want/need. The SMC Pentax M* 300/4 would be nice and by all accounts is a much better lens than the K 300/4. The K 300/4 displays a lot of purple fringing and chromatic aberrations in high contrast situations. The K 85/1.8 is also on my want list and is generally regarded as being a better optic than the M 85/2. It is a little faster and commands a considerably higher price if you can find one. Perhaps the fact the production run of the K series was quite a bit shorter has something to do with the perception they are better. Scarcity tends to drive the price up as a rule.

Tom G

Last edited by 8540tomg; 02-19-2012 at 12:45 PM. Reason: typo
02-19-2012, 02:41 PM   #15
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Stan's pentax has opinions, but for one major criteria (resolution) see the following where almost all M and K's, in the 18-135 mm range, are tested.
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