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08-30-2012, 02:33 AM   #1
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SMC-A 135/2.8 vs Revuenon

Hello.

I bought week ago Pentax SMC-A 135/2.8. Build quality is nice, manual focus feel is the best I experienced so far, but resolution/sharpness is quite not that I expected. If I close lens to 7.1 everything is sharp.

Here are some samples took using smc-a 135/2.8 and revuenon 135/2.8 (which cost me 1/4 of pentax).
https://www.dropbox.com/sh/2v52tt84ekh4qzm/wXSSkzzX6y

Direct urls:
Revuenon @ 2.8, border
https://www.dropbox.com/sh/2v52tt84ekh4qzm/mAQHAbQ3RY/135revu2_8_border.JPG
Pentax @ 2.8, border
https://www.dropbox.com/sh/2v52tt84ekh4qzm/pfLdfbq394/135smc2_8_border.JPG

Is it normal, or my unit has flaws?

08-30-2012, 03:09 PM   #2
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Join Date: Mar 2010
Location: Frankfurt am Main
Posts: 1,088
It is impossible to state what really caused these results. There are many many possible reasons.

But generally about these 2 lenses: a couple of years ago there was a detailed test by a German amateur tester of a range of Pentax 135mm lenses (old and new), and he used just this Revuenon lens to compare.

The site does not exist anymore, but I had downloaded the PDF.
A small exerpt of the scoring (possible maximum = best = 10, first value is the Pentax-A, second value the Revuenon):

Distortion 9/9
Vignetting 8/8
Bokeh center area 8/8
Bokeh border area 8/8
Color errors center area 5/5
Color errors border area 6/4
Resolution real life F2.8 6/3
Resolution charts F2.8 8/7
Resolution real life F4 6/6
Resolution charts F4 8/8
Resolution real life F5.6 7/6
Resolution charts F5.6 8/8

This indicates there is no area where the Revuenon is better than the Pentax-A, but some points where the Pentax-A is significantly better. But the tester resumed that also the Revuenon is one of the really good 135mm lenses.
BTW, champ of this test was the Pentax-F, second the Pentax-A (by a very small margin), probably only caused by slightly better coatings.

EDIT: The Pentax-A was in fact the SMC Pentax-A, and the better results of the Pentax-F was NOT caused by better coatings, see my posting further down.

Last edited by RKKS08; 08-31-2012 at 02:58 AM.
08-30-2012, 03:38 PM   #3
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Original Poster
It's the first time when I'm not fully satisfied with Pentax lens. Maybe this Revuenon is exceptionally good . Maybe someday I'll buy another A version, or something more modern. Pentax-F is quite expensive and rare, I think.
08-30-2012, 03:55 PM   #4
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After reading the full text of the 26-pages review, I must apologize for a mistake in my previous posting: the Pentax-F obviously is not better than the Pentax-A because of coatings, but mainly because resolution in border areas is visibly better.

As your examples show shoots with open aperture, here a rough translation from German to English of the resuming/explaining text of the real life comparison at F2.8:
QuoteQuote:
Here the Pentax-F ist the best lens. It delivers sufficient contrast and good sharpness over the complete area. Only slightly worse is the Pentax-A, which is as sharp in the center, but gets a bit softer at the borders. Third is the Takumar Bayonet 2.8 which is only very slightly worse than the 2 best lenses. Followers are the Pentax-K and Pentax-M with visibly worse resolution, mainly at the corners. The Revuenon offers visibly worse sharpness and less contrast than the K and M, and the Takumar Bayonet 2.5 is very soft and offers much less contrast than even the Revuenon.
I should also mention that the tests were done with a 10MP Pentax K200D. Resolution tests could work out slightly different with a 16MP sensor. But this can in no way account for the results you posted.

08-30-2012, 06:27 PM   #5
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The not so common A 135mm f/2.8 delivers decent but average performance. The 4 element in 4 group construction cannot compare to the newer and optically superior F and FA 135mm f/2.8 versions. Wide open performance is soft, no wonder it is not one of the better performing A series lenses around.
08-31-2012, 12:15 AM   #6
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@creampuff:
I forgot to mention that the Pentax-A in the test was the SMC version. The Takumar Bayonet 2.8/135 indeed was sold in some countries named Pentax-A 2.8/135 and had a multi coating, but not the SMC one. However, the above mentioned test showed the difference between the SMC-A and the Takumar Bayonet only with intense pixel peeping. Even the difference concerning flare was marginal. The Takumar Bayonet 2.5 suffered badly from flare - as the optical design is the same for the 2.8 and the 2.5 versions, probably the coatings make all the difference. I think Pentax improved the coatings of the Takumar Bayonet versions all the time, and the last versions were near to the SMC. The tester may have - without knowing - compared a late copy of the 2.8 with an much earlier one of the 2.5.

I would not blame too much the 4/4 optical design for inferior resolution. Some of the sharpest macro lenses use this design. If you ignore color correction, you can build 4/4 135mm lenses for FF with outstanding resolution down to F4, with not too much degrading also at F2.8.

BTW, I myself own the Takumar Bayonet 2.8, and I am very satisfied with its performance. For a while, I also owned the Porst 2.8/135, which was visibly worse than the Takumar in respect to border resolution and contrast (at F2.8 and F4) and flare. But even the Porst I would call a decent lense. It seems in the eighties there were no really bad 135mm lenses.

EDITED to add some points.

Last edited by RKKS08; 08-31-2012 at 12:31 AM.
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