Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-28-2018, 08:01 AM   #1
Pentaxian
cyberjunkie's Avatar

Join Date: Mar 2010
Location: Chiang Mai, Bologna, Amsterdam
Photos: Gallery
Posts: 1,198
Smc Pentax 2.8/105mm vs Pentax-M/A 2.8/100mm

Has anybody ever tried to compare the two lenses?
In general I appreciate very much the early Pentax-K series, that in general was built without cutting corners, both mechanically and optically.
IMHO few focals have increased their performance from K to M and A.
There are exceptions, like the A Star's, the Pentax-A Macro 2.8/100, and the Pentax-A 4/200mm, but most other focals/types have worse mechanics and simpler optical layouts.
In this case the two designs are not very different: the earlier model has a cemented doublet at the back, the newer version (M and A) has two air spaced elements.
In theory it looks like the advance in coating technology allowed for two more glass-to-air surfaces and and a higher degree of freedom in aberration correction (theoretically an air spaced doublet is more efficient than a cemented one).
In practice... I have no idea
The old Auto Takumar 1.8/85mm, with five elements and released in 1960 (!), is almost as sharp as the Pentax-M 2/85mm, has better bokeh and overall rendering, and shows almost no fringing. In a few words, it trashes its younger sibling.
When it comes to 100/105mm lenses, I really have no idea. I guess the only way to know is to ask those who have/had the chance to actually try both lenses.


I have a similar problem finding a cheap AF zoom that goes down to a minimum focal of 24mm.
I have the FA 24-90mm (but I don't have it with me), and I recently eyed a nice F 24-50mm sold for a nice price.
Is really the latter better than the former?
The zoom range is not so important, I just want a wide angle zoom with good sharpness and controlled CA.
The user reviews are not easy to interpreter, and there is no direct comparison...

10-28-2018, 08:10 AM - 1 Like   #2
Loyal Site Supporter
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: Working From Home
Photos: Gallery | Albums
Posts: 26,276
IMO both the K105 and the M100 are nice, sharp medium telephoto lenses with good color fidelity and contrast. I have both the K and M ATM, but I’m selling all my manual lenses except the K’s. In my experience the M renders somewhat cooler - presumably caused by coating evolution - perhaps has a touch more contrast (though many would argue the point) and is a joy to use mechanically, just like the K. I can’t make a strong argument for one over the other except that I use K film bodies and the K lenses balance better on them (and I think also on the K-1),
QuoteOriginally posted by cyberjunkie Quote
Has anybody ever tried to compare the two lenses?

.:

In general I appreciate very much the early Pentax-K series, that in general was built without cutting corners, both mechanically and optically.
IMHO few focals have increased their performance from K to M and A.
There are exceptions, like the A Star's, the Pentax-A Macro 2.8/100, and the Pentax-A 4/200mm, but most other focals/types have worse mechanics and simpler optical layouts.
In this case the two designs are not very different: the earlier model has a cemented doublet at the back, the newer version (M and A) has two air spaced elements.
In theory it looks like the advance in coating technology allowed for two more glass-to-air surfaces and and a higher degree of freedom in aberration correction (theoretically an air spaced doublet is more efficient than a cemented one).
In practice... I have no idea
The old Auto Takumar 1.8/85mm, with five elements and released in 1960 (!), is almost as sharp as the Pentax-M 2/85mm, has better bokeh and overall rendering, and shows almost no fringing. In a few words, it trashes its younger sibling.
When it comes to 100/105mm lenses, I really have no idea. I guess the only way to know is to ask those who have/had the chance to actually try both lenses.


I have a similar problem finding a cheap AF zoom that goes down to a minimum focal of 24mm.
I have the FA 24-90mm (but I don't have it with me), and I recently eyed a nice F 24-50mm sold for a nice price.
Is really the latter better than the former?
The zoom range is not so important, I just want a wide angle zoom with good sharpness and controlled CA.
The user reviews are not easy to interpreter, and there is no direct comparison...
.:

Last edited by monochrome; 10-28-2018 at 07:02 PM.
10-28-2018, 09:19 AM - 1 Like   #3
Site Supporter
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 8,076
I've got the K105/2.8 and the M100/2.8. As Paul said both are good, but I prefer the K105/2.8 overall.

Note my comparisons were on film, so not sure on digital.

Phil.
10-28-2018, 03:04 PM   #4
amateur dirt farmer
Loyal Site Supporter
pepperberry farm's Avatar

Join Date: Dec 2014
Location: probably out in a field somewhere...
Photos: Gallery | Albums
Posts: 41,131
QuoteOriginally posted by cyberjunkie Quote
I have a similar problem finding a cheap AF zoom that goes down to a minimum focal of 24mm.
I have the FA 24-90mm (but I don't have it with me), and I recently eyed a nice F 24-50mm sold for a nice price.
Is really the latter better than the former?
The zoom range is not so important, I just want a wide angle zoom with good sharpness and controlled CA.
The user reviews are not easy to interpreter, and there is no direct comparison...

APS-C or FF?

10-28-2018, 06:16 PM   #5
Site Supporter
Site Supporter




Join Date: Dec 2012
Location: Essex, Ontario
Posts: 682
As above, I agree that the 105 K has the special build and image rendering seen in many of the SMC K models. Even though the 100 M was a good, sharp lens and I saw it at a reasonable price when it came out, I was never tempted. More recently a 105 found it's way between my 85 f1.8 and 135 f2.5. Yeah, partial to K.
10-29-2018, 01:59 AM - 1 Like   #6
Pentaxian
LennyBloke's Avatar

Join Date: Aug 2008
Location: Worcestershire, UK
Photos: Gallery
Posts: 675
I tend not to do direct comparisons of lenses but over the years I have owned both of these lenses several times and the one that stood out for me was the Pentax SMC A 100mm f2.8 - I can't disagree on the comments on the mechanical engineering of the K series lenses (it still brings a smile to my face when I focus the K28/2.0) but I think the A is a beautifully compact, smooth focusing, sharp lens and one I'm keeping hold of
10-29-2018, 02:41 AM   #7
Pentaxian
cyberjunkie's Avatar

Join Date: Mar 2010
Location: Chiang Mai, Bologna, Amsterdam
Photos: Gallery
Posts: 1,198
Original Poster
QuoteOriginally posted by pepperberry farm Quote
APS-C or FF?
Forgot to specify, but my everyday camera is my signature
I use FF 99% of the times.
Corner performance is not an issue.
Just trying to understand if the rendering of the 100mm differs in any visible way from the 105mm.
Owning a Pentax-A 2.8/100mm would make for an important improvement in usability, and allow P-TTL flash, but I'm not so sure it's worth it if the two lenses have a very similar optical signature.

cheers
Paolo

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!
2.8/105mm vs pentax-m/a, air, elements, idea, k-mount, lenses, pentax 2.8/105mm vs, pentax lens, pentax-a, slr lens, smc pentax 2.8/105mm
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
SMC PENTAX D-FA 100mm WR vs SMC Pentax F 100mm SunnyG. Pentax SLR Lens Discussion 14 09-06-2017 06:13 PM
K-5 vs MZ-S vs LX vs PZ-1p vs ist*D vs K10D vs K20D vs K-7 vs....... Steelski Pentax K-5 & K-5 II 2 06-28-2017 04:59 PM
SMC 105mm F2.8 vs SMC-M 100mm F2.8 Lowell Goudge Pentax SLR Lens Discussion 5 12-09-2015 03:56 PM
DFA 100mm vs. FA 100mm vs. Sigma 105mm PentaxForums-User Pentax SLR Lens Discussion 9 08-22-2010 05:25 PM
Pentax DFA 100mm f/2.8 Macro vs Sigma 105mm f/2.8 EX DG vs Tamron AF 90mm f/2.8 Di SP dyusem Pentax SLR Lens Discussion 2 02-13-2010 08:11 PM



All times are GMT -7. The time now is 10:32 PM. | 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