Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-24-2013, 05:25 PM   #1
Site Supporter
6BQ5's Avatar

Join Date: Jun 2013
Location: Nevada, USA
Photos: Albums
Posts: 3,108
Optical differences between Pentax "K", "M", and "A" lenses

I'm sure that this has been asked and answered before but it's hard to search for this. What is the optical difference between the "K", "M", and "A" series of Pentax lenses? It's hard to search for this because a lot of search engines turn off single character entries in the string.

I understand that the "A" lenses allow for the camera body to control aperture. My question is about the optics/glass.

Thanks!

06-24-2013, 05:31 PM   #2
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,863
I think most of the info you need is right here.

Pentax Lenses - Pentax Lens Reviews & Lens Database

Anything that isn't is probably here.

Pentax K-Mount Lenses and Lens Accessories
06-24-2013, 05:35 PM   #3
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,770
The two main sources of information are the database on this site, here: Pentax Lenses - Pentax Lens Reviews & Lens Database

And Bojidar Dimitrov's site here: Pentax K-Mount Lenses and Lens Accessories

In some, even many, cases the optics are the same as the series changed. In other cases they changed quite a bit. You have to look at the individual lenses.

For example the 50mm f/1.4 in 'K' mount has 7 elements in 6 groups and a 52mm filter, the 'M' version 7 elements in 6 groups and a 49mm filter, the 'A' version 7 elements in 6 groups with 49mm filter.
06-24-2013, 05:36 PM   #4
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,770
You beat me Boriscleto

06-24-2013, 05:50 PM   #5
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,623
The K often were same as the SMC takumars--although some increase in number of elements (e.g., 28mm f3.5) happened to tweak the performance. Size of the lens was not primary consideration.

With M lenses size was very important--many are reduced in number elements and filter size dropped from 52 to 49mm--as a result I believe it is fair to say most of us consider the M lenses to be weaker than their K counterparts. BTW the K lens is not an official name for them.

Some of the A lenses carried over the M formulas--although also a number of faster (larger) lenses were added. For some of the very wide angle lenses (>/= 20mm), and the zooms, the latter formulations are better--although that is debatable for certain lenses (e.g., the 15mm f3.5). Anyway for primes usually the K are considered better, then A, then M (but again there are exceptions--e.g., the 50mm f1.4 is I believe reputed to be better with the A/FA) .
06-24-2013, 05:53 PM   #6
Pentaxian
carrrlangas's Avatar

Join Date: Mar 2012
Location: Joensuu (Finland)
Photos: Gallery
Posts: 1,750
I might be completeley wrong but from what IŽve read, it seems the A series is where Pentax redesigned most of (or took the best of) the lenses and also improved the coatings. From there onwards there was little improvement, leaving aside newer desings that incorportate ED elements, Internal Focusing (IF) and aspherical lens (AL)
06-24-2013, 06:02 PM   #7
Site Supporter
kiwi_jono's Avatar

Join Date: Dec 2009
Location: Christchurch, New Zealand
Photos: Gallery | Albums
Posts: 1,083
As others have said, but I can confirm from direct experience that the A50 f1.4 is a little bit better at larger apertures than the M50 f1.4 (which is still a lovely lens - especially mechanically) - at least in my copies (and the M is mint).

I also have the K28 f3.5 and its the best 28mm I have (for lack of distortion and general sharpness across the frame).
06-24-2013, 06:12 PM   #8
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,623
BTW your question should ideally be answered with more detail--was it resolution (center and corner), or comma, or distortion, chromatic aberrations, curvature of field, etc. But this level depends on each lens--and testing is generally not available and/or may not be valid. In my case I tend to pick individuals that have used/tested lots of Pentax lenses and whose comments on a few lenses seems to make sense/are consistent with my likes/dislikes--and then I go with their comments on all the other lenses. Not very scientific--but not much else to go by.

But (for example) an additional element may/should reduce some of the lanes aberrations--but may not improve center resolution, and likely will make flare a bit worse. So what is "better performance?" And certainly (IMO) size is part of performance--a lens that feels right will make us do a bit better.

06-24-2013, 06:32 PM   #9
Veteran Member




Join Date: Nov 2006
Location: central Singapore
Photos: Gallery
Posts: 409
QuoteOriginally posted by 6BQ5 Quote
I'm sure that this has been asked and answered before but it's hard to search for this. What is the optical difference between the "K", "M", and "A" series of Pentax lenses? It's hard to search for this because a lot of search engines turn off single character entries in the string.

I understand that the "A" lenses allow for the camera body to control aperture. My question is about the optics/glass.

Thanks!
I have the K and M versions of the 50/1.4 and 28/3.5 - I have a general, non-scientific sense that the K versions are slightly superior, but frankly I think the difference is so small that you can ignore it for practical purposes. I have the K105/2.8 and the M100/2.8 - in this case I prefer the M lens, particularly wide open. Again, the difference is minor. I have been extremely happy with all of them. The compactness/lightness advantage of the M series is a real consideration.
06-24-2013, 07:13 PM   #10
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,795
the K series lenses were designed to be used with the higher tier pentax bodies - the M series were designed to be more compact, better suited to smaller cameras like the MX and ME super, the A series was a bit of a return to the K series Ideal of providing wider apertures. The lens that changed the most through the K>M>A Generations would be the SMC-K 28mm f/2 "hollywood" lens. Many K mount lenses were reiterated and improved with the A series, with improved coatings and the added coupling for aperture control - but also a manual aperture ring that allowed for full manual control on older camera bodies.
06-24-2013, 07:52 PM   #11
Site Supporter




Join Date: Nov 2012
Location: Saint Paul
Posts: 304
QuoteOriginally posted by carrrlangas Quote
I might be completeley wrong but from what IŽve read, it seems the A series is where Pentax redesigned most of (or took the best of) the lenses and also improved the coatings. From there onwards there was little improvement, leaving aside newer desings that incorportate ED elements, Internal Focusing (IF) and aspherical lens (AL)
I have A-50/1.4 and FA-50/1.4 and from my visual inspection both have identical optics.
06-24-2013, 08:10 PM   #12
Pentaxian
carrrlangas's Avatar

Join Date: Mar 2012
Location: Joensuu (Finland)
Photos: Gallery
Posts: 1,750
QuoteOriginally posted by TropicalMonkey Quote
I have A-50/1.4 and FA-50/1.4 and from my visual inspection both have identical optics.
And I remember reading that the A version has new coatings compared to M version and some of the elements where redesigned.
06-24-2013, 08:42 PM   #13
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,735
QuoteOriginally posted by Digitalis Quote
the K series lenses were designed to be used with the higher tier pentax bodies - the M series were designed to be more compact, better suited to smaller cameras like the MX and ME super,
The M series was also marketed as the line
for use on the LX professional body,
except for special cases like the 24/2.8, 30/2.8 and 50/1.2
which needed a 52mm filter size rather than the standard 49mm of the M series.
(Strangely enough, the 200/4 and 400/5.6, which also took bigger filters,
were nevertheless designated as M lenses.)
06-24-2013, 09:03 PM   #14
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,735
QuoteOriginally posted by dms Quote
Some of the A lenses carried over the M formulas.
The M28/2.8 is like that, but in some other cases,
like the 24/2.8 and 50/1.2,
the A lenses took the K lens formula
(although the coatings have been said to be improved),
and there never was an M version with those focal length/aperture combinations.

QuoteOriginally posted by dms Quote
For some of the very wide angle lenses (>/= 20mm), . . . the latter formulations are better--although that is debatable for certain lenses (e.g., the 15mm f3.5).
I own, and use, three 20's
(it's a favorite walk-around focal length for me):
the S-T 20/4.5, the M20/4, and the A20/2.8.
Each has its own strengths and weaknesses,
although technically the A20/2.8 is indeed better
(same formula as the FA 20/2.8).


QuoteOriginally posted by dms Quote
Anyway for primes usually the K are considered better, then A
For the 24/2.8, where the K and A share the same formula,
the coatings in the A seem to be an improvement.
For the 50/1.2, the same seems to be true,
although some users do prefer the K to the A.


QuoteOriginally posted by dms Quote
then M (but again there are exceptions--e.g., the 50mm f1.4 is I believe reputed to be better with the A/FA) .
Since I do a lot of shooting at infinity,
I've found the M, with its flatter cemented join,
to give excellent performance.
Other users, who work more at short range,
prefer the K or A formulas with more curvature at that join.
06-24-2013, 09:54 PM   #15
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,735
QuoteOriginally posted by dms Quote
With M lenses size was very important-- . . . --as a result I believe it is fair to say most of us consider the M lenses to be weaker than their K counterparts.
I don't look at it that way.

To me, the philosophy of size reduction that drove the design of the M line
is the same philosophy, engrained deep in the Pentax DNA,
that later led to the Limited lenses in the FA and DA series.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, lenses, pentax, pentax lens, search, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Don't say Pentax "Q" in French ... "Q" = "cul" = "A--" Jean Poitiers Pentax Q 52 11-10-2013 06:25 AM
ME super: can I use "M" lens in "auto" setting. treetoile Troubleshooting and Beginner Help 4 03-25-2013 10:03 AM
People K-30 - 1st "Shoot" - "A Girl & Her Bike" Julie Post Your Photos! 8 09-01-2012 09:38 AM
difference between "focus indicator" with "matte field" cmrhm Pentax K-5 3 07-31-2012 02:12 PM
Difference between "Delete All" and "Format"? wedge Troubleshooting and Beginner Help 13 03-20-2012 10:37 AM



All times are GMT -7. The time now is 04:46 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top