[cyberjunkie]

I already wrote about it in another post, some time ago. Most Smc Pentax lenses (usually called Pentax-K for clarity) have more complex optical designs than successive manual focus series.
This is generally true in regard to primes, which in general have "more glass" in them than other Pentax optics, including AF ones.
I gave a thought about that, and I'm starting to believe that the K lenses, albeit often derived from dated SMC Takumar designs, are often "better" than later releases.
I'm not so sure that the re-designs of the M series were only due to the need to contain weight and size (passed - for the most part - down to the A generation), I guess there could have been cost issues involved.
Probably we'll never know the truth, but my own personal experience seems to confirm that the Pentax-K are on average very good, often "better" ( at least according to my very personal, and highly debatable, meter).
I've thrown my stone in the pond!

Now just a couple of examples from two lenses I just acquired...
Usually I don't upload full-res pictures to Flickr, and almost never portraits or pictures could ever be stolen, but this time the photos are so irrelevant that I decided to post un-resized JPGs to allow for pixel peeping.
The first shot is a test before opening a fungus infested 3.5/28mm.
Here is the fungus:



It's the ugly fence that sits half-built on the side of my house.
The cement pole has enough detail to check for sharpness. Click to have access to Flickr, it will be allowed to download it at the original size.
Converted with Iridient Developer, with default setting. It's way underexposed (I didn't want to do any correction in PP), but the correctly exposed one, also available on Flickr, was shot wide open and is not fully in-focus.
This one was shot stopped down one or two clicks:



Here is another shot, wide open, with a 105mm f/2.8. Very nice rendition, IMHO:




I'd be interested in other opinions.
Personally, I think most K lenses are great!

cheers

Paolo

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Last edited by cyberjunkie; 01-06-2018 at 05:24 AM.

[JimD]

I've got a K200:f4 and a M200:f4. Only one comparison but I would say that, in my opinion, there is no difference. One is not better than the other.

[timw4mail]

I already wrote about it in another post, some time ago. Most Smc Pentax lenses (usually called Pentax-K for clarity) have more complex optical designs than successive manual focus series.
This is generally true in regard to primes, which in general have "more glass" in them than other Pentax optics, including AF ones.
I gave a thought about that, and I'm starting to believe that the K lenses, albeit often derived from dated SMC Takumar designs, are often "better" than later releases.
I'm not so sure that the re-designs of the M series were only due to the need to contain weight and size (passed - for the most part - down to the A generation), I guess there could have been cost issues involved.
Probably we'll never know the truth, but my own personal experience seems to confirm that the Pentax-K are on average very good, often "better" ( at least according to my very personal, and highly debatable, meter).
I've thrown my stone in the pond!

The build quality is generally better on older series of lenses, yes. Optical formulas don't change much, though.

The K and M series lenses didn't generally have different optical formulas, just different bodies. The M-series lenses were generally closer in size to their Takumar equivalents.

[monochrome]

I think it is hard to generalize. Some A lenses are classics and some K lenses are simply outstanding. I suppose the obvious response it it depends how you define good. They’re some hat different. The coating evolved over time. IMO K lenses render slightly warmer than M and A lenses, which is the only broad observation I can make.

[IgorZ]

I've never made a direct comparison, but the only comparable lenses I've had were M 28 f2.8 and K 28 f3.5. I must admit that I sold the M. I can't say it was worse, it was just different. More saturated colours for sure. But I liked the rendering of the K a lot. A lot more than the M.

[sibyrnes]

The K and M series lenses didn't generally have different optical formulas, just different bodies. The M-series lenses were generally closer in size to their Takumar equivalents.

That is not accurate and a quick look at the forum's lens data base will confirm that. The K 20mm, 28mm, 35mm and 135mm are definitely different(and superior in my opinion) to their M equivalents. I mention them because they are the ones that I am most familiar with but it is generally true through out the line. The most obvious difference is the filter sizes - many of the M series are smaller.

[cyberjunkie]

I thought most people would check the differences on Bojdar Dimitrov's site, or the new Pentax-K site that is replacing it (kmp.pentaxians.eu).
The general trend in replacing older designs with less complex ones is quite evident.

Yes, i expect the 4/200mm to be roughly equivalent. Never owned the K, sold long time ago the M, and i'm waiting for the A in the mail. In this case the three lenses have three different layouts (respectively 5/5, 5/6 and 6/6). This specific speed/focal is definitely not following the trend. The 2.5/200 was a 6elements/6groups though, and it's almost unanimously considered a better performer. Never had it cause i purchased the A* 2.8/200mm long long time ago... in this case, the newer the better.

I am going to give just a few examples:

15mm: K and A are identical, no M version
20mm: K f/4 12/10; M f/4 8/8, A f/2.8 10/9
24mm: all are 9/8, but the early K f/3.5 version has a different (most say better) design; no M version
2/28mm: K f/2 9/8; the others (M and A) are 8/7
other 28mm: here the difference is impressive, K shift 12/11; K f/3.5 8/7; M f/3.5 6/6; M f/2.8 (both versions) 7/7; A f/2.8 7/7; F 7/7; FA 5/5
2/35mm: K 8/7; M and A 7/7

I'm stopping here other way it gets tiring, but there are other examples i remember, like the 135mm. The K 2.5/135 has 6/6, both the M f/3.5 and the A f/2.8 have 4/4...
Of course more elements don't mean more IQ, but interestingly modern primes have a high number of elements, for a better correction of aberrations.

K lenses have, on average, a slightly more complex optical layout, and were designed more or less using the same information/technologies as M and A lenses. Few years of difference
How this works in practice differs from one objective to the other, but it is a fact.

cheers

Paolo

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Last edited by cyberjunkie; 01-06-2018 at 10:58 PM.

[sibyrnes]

I've got a K200:f4 and a M200:f4. Only one comparison but I would say that, in my opinion, there is no difference. One is not better than the other.

According to the forum database, the K200 f4 takes a 58mm filter and the M200 f4 takes a 52mm filter - definitely a difference in optical formula. "Better" is a subjective term, but there are physical difference between almost all of the K and M series.

[gofour3]

I'd be interested in other opinions.
Personally, I think most K lenses are great!

I would agree that the K series version is usually my favourite over the M or A series equivalent.

I find the K series are usually equal or slightly better optically and the handling is always better that the "M" & "A" equivalent. The build is better than most "regular" A Series lenses as well.

The exception are the more elite A Series lenses like the A16/2.8 & A20/2.8 or any A* lens. I find these are the equal or better then the K Series equivalent.

Phil.

[lesmore49]

Not being an optical engineer, I don't know if modern lenses are better. I do know that my old (bought new in '84) Pentax 35-105 A Macro zoom lens is one very fine lens. Always happy with the picture quality and the construction, albeit heavy, is better than most of my modern lenses, I would say. Again I'm a lay person, wouldn't claim to be an expert in these matters..

[Wild Mark]

For the sake of brevity, K series is better, optically with exceptions mentioned by Phil + A28/2, A35/2 and A50/1.2. With regards to the A28/2 I can say there is little difference to the K28/2, with smaller design making it quite useful. The same can be said for the A35/2.

In the main, K series is optically different to M and A series because the design brief was different - miniaturisation

[kiwi_jono]

I have a K 28 f3.5, its the most optically complex and certainly it seems to have better sharpness across the frame than the subsequent 28mm lenses (although I'm excluding f2 variants as I don't know how they compare).
However sharpness is not everything. For example I have a FA28 f2.8 and compared to the K28 f3.5:
* K build is fantastic - far better than FA
* K manual focus is fantastic but FA finicky to manual focus.
* Centre sharpness much the same - wide open K slightly better but stopped down there the FA possibly pulls ahead slightly.
* Corner sharpness, wide open is better on the K than FA (but FA catches up to K stopped down to say f8)
* FA is more flare resistant
* FA seems to exhibit less CA than K
* FA is significantly smaller and lighter than K
* I like the colours much better on the FA better than the K.
* FA has the obvious advantages of AE and AF.

Based off that I prefer the FA over the K and the thing that swings it for me is I like the colours of the FA better than K. From tests I have done previously with a A28 f2.8, I would say that the FA may have an edge on sharpness across the frame (possibly the "AL" coming into play?).
But of course bear in mind sample variation is a factor too and some samples are better than others.

[cyberjunkie]

However sharpness is not everything. For example I have a FA28 f2.8 and compared to the K28 f3.5:
.....

Spot-on.
Sharpness isn't everything. And element number can't be compared between lenses using different technologies. The FA is just a 5/5, but one element is aspherical, IIRC.
Aspherical elements allow to correct aberrations using a simplified lens design, sparing optical glass and containing size.
It was extremely complicated, and expensive, using all-glass elements, but the introduction of aspheric elements partly made of molded plastic has been a game changer.
I have both the Asahi/Zeiss 2/28 and the K3.5/28 (just acquired, to be cleaned from fungus), plus the shift version. I'm fine with them now, but before I had in mind to buy the FA, which I'm sure is a great lens (and has electric contacts and AF).
I know that element counting is not meaningful in itself.
Probably I should have worded the title of the thread in a more precise way. Something like "Is it true that K lenses are better than their M counterparts, and often other later versions too?".
I don't know if such long title would be allowed, though

I would agree that the K series version is usually my favourite over the M or A series equivalent.

I find the K series are usually equal or slightly better optically and the handling is always better that the "M" & "A" equivalent. The build is better than most "regular" A Series lenses as well.

The exception are the more elite A Series lenses like the A16/2.8 & A20/2.8 or any A* lens. I find these are the equal or better then the K Series equivalent

I don't have the fisheye, but I wholeheartedly agree with your point. The A series introduces a distinction in the family of Pentax optics. There are A and B members.
The process started with the Pentax-M* 4/300mm.
All the K lenses were built the same. Almost all the M were made the same (with simpler designs and reduced bulk/weight). A lenses fall in two different category.
Cheaper ones inherited M designs, and plastic parts were introduced.
More expensive ones still had a very good build quality, and introduced more ambitious, state-of-the-art optical designs, also using "special" optical glass.
I agree with you that these higher standards were not limited to the new A Star's.
I have a few A series lenses that are almost identical, or either sharper or faster than their older cousins.
The A 3.5/15mm, A 2.8/20mm, A 2/35mm, A* 1.4/85mm, A* 2.8/200mm and A* 2.8/300mm were among my favorite MF lenses.
Now the 2.8/14mm and 1.4/35mm by Samyang have supplanted two of them... but a lot of water has flown under the bridges in the meantime!
IMHO some K series lenses can proudly stand close to some of the great manual focus optics in Pentax K mount, and supplement (at a fraction of the cost) a line-up of high-quality, expensive lenses.
Compared to most second tier Pentax objectives, the K series provides more than average IQ and better build.
According to my taste, the best build is found in Super-Multi-Coated Takumar's, but I don't think it makes much sense to compare M42 with PK lenses.
I see screw-mount objectives as "project lenses", better used when there is plenty of time, and when i know I will use the same lens for the entire shooting session.
Going back and forth between M42 and PK is not so pleasant, and would eventually dirt the sensor.
The pleasure of using the best mechanic doesn't compensate for the hassle of mounting/removing the adapter every time. If a body is dedicated to M42, or a single objective is used for the entire time, I still enjoy M42 lenses. Not so much for a more conventional use.
All this to say that I'm not so old/stiff/embittered to think that back in the old golden times everything was better... I'm just trying to make sense of a simple observation:
from K series to M series there was a sudden, consistent reduction of lens elements, and the disappearance of most collated doublets from the design of many optics.
Personally I'm brought to believe that there was a reason (maybe two or three *), and that there were consequences (read: some of the new designs didn't perform as good as the old ones).

* the third possible reason could have been the programmed disappearance from the market of lead-based optical glass.


cheers

Paolo

[pschlute]

but the only comparable lenses I've had were M 28 f2.8 and K 28 f3.5. I must admit that I sold the M. I can't say it was worse, it was just different.

The K 28mm 3.5 is widely regarded as one of the best lenses of it's era, for sharpness and contrast in particular. The M 28mm 2.8 although a fine lens (Pentax didn't really make any duds in that time) was a very common lens, affordably priced and part of every Pentax users kit. Not really a fair comparison. The Pentax -M 28mm f2 (or M 28mm 3.5) is probably a more comparable lens.

[pinholecam]

I think its the general direction of the product lines that define the K and M series, and the often indirect consequence is the number of glass elements and heft.

As to which is better, I think it depends on what we define 'better'.

There is just no K equivalent to my M20/4 for portability at 20mm.
The M85/2, has a more painterly bokeh than my K85/1.8, though the latter is sharper and CA resistant from wide open. The M85, then wins again with a super portable size. Yet, the M85 has fewer aperture blades and hex shaped OOF can occur more often than the K85......
The K28/3.5 really sets the standard against most other 28mm for stopped down shooting. However, the M28/3.5 is indeed far smaller and really very sharp for nearer focus stuff (but the edges lose out for infinity).
The K501.4 is heavier, the M50/1.4 does exactly the same job for lighter.

And the pros/cons of each goes on...