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05-02-2009, 07:30 PM   #16
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QuoteOriginally posted by frank Quote
On my K20D, the Sigma 1770 does seem to be a better lens, sharper at almost all focal length and aperture settings except at the very wide end where the Pentax one is sharper wide open
I wouldn't call 40mm "the very wide end". Here are the MTF50 results (again) from photozone.de:

At f/4, 40mm, Mr. Pentak gives you
2028 (center), 1885 (border).

At f/4, 35mm, Mr. Shiguma gives you
1888 (center), 1825.5 (border).

05-03-2009, 04:36 AM   #17
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QuoteOriginally posted by axl Quote
there was a time when Sigma 17-70 had quite a following, many people were really into this len, and how sharp it was, etc...
Never heard that much about Pentax 17-70, it was announced, it came, some people got it and that was just about it, never some big WOW, or something..
The Sigma was the first lens with this zoom range. Pentax came rather late with this range and it is more expensive. I used the Sigma 17-70mm for some 2 years and now I have the DA17-70mm. Both lenses are quite good. The IQ of the DA17-70mm is quite similar to that of the DA16-45mm. The Pentax lens has some advantages overe the Sigma, such as the dirt resistant SP-coating and Quickshift.

In my country the DA17-70mm is too expensive. It is far cheaper in the UK where I bought my copy.
05-03-2009, 04:42 AM   #18
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QuoteOriginally posted by Parallax Quote
The 70mm f4 and f8 shots in test look more like motion blur to me, not lens softness.
At 70mm the pictures are slightly sharper at aperture f11 than at aperture f8.0. A lot depends on focussing. The focussing range is quite short so you can misfocus quite easily.
05-03-2009, 07:23 AM   #19
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QuoteOriginally posted by asdf Quote
I wouldn't call 40mm "the very wide end". Here are the MTF50 results (again) from photozone.de:

At f/4, 40mm, Mr. Pentak gives you
2028 (center), 1885 (border).

At f/4, 35mm, Mr. Shiguma gives you
1888 (center), 1825.5 (border).
Then either the Pentax 1770 I got was a lemon, or the Sigma one photozone tested wasn't as good as mine

05-03-2009, 07:39 AM   #20
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QuoteOriginally posted by frank Quote
Then either the Pentax 1770 I got was a lemon, or the Sigma one photozone tested wasn't as good as mine
Yes, because lenses--and not people--shoot photographs: the photographer never contributes to the result.

photozone's copy of Mr. Pentak's lens was imperfect: it had a de-centering defect. It still wins against Mr. Shiguma at ~40mm.

Last edited by asdf; 05-03-2009 at 07:51 AM.
05-03-2009, 07:39 AM   #21
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QuoteOriginally posted by Hythloday Quote
At 70mm the pictures are slightly sharper at aperture f11 than at aperture f8.0. A lot depends on focussing. The focussing range is quite short so you can misfocus quite easily.
At f/11, it should have been softer than at f/8 because of diffraction. That guy had no idea what he was doing.

Last edited by asdf; 05-03-2009 at 07:53 AM.
05-03-2009, 08:15 AM   #22
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QuoteOriginally posted by asdf Quote
At f/11, it should have been softer than at f/8 because of diffraction. That guy had no idea what he was doing.
I superficially test a lens and I shot a registration number from some distance. At aperture f/11 it was slightly sharper than at aperture f/8 at 70mm. It mostly depends on focussing. If the lens is correctly focussed, the images will be very sharp indeed. The photographer should take time to do some proper focussing. I like the DA17-70mm very much and I have used it during 9 photo series. Below you find some images shot with the DA17-70mm:



05-03-2009, 08:41 AM   #23
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Excellent shots Hythloday! Are those HDR?

I have only used the sigma 17-70 and it is definitely the ideal vacation lens for me. One thing to add to consideration is that the sigma has a really close focusing distance (essentially as close as youre willing to put the front element to the subject) and a max magnification of 1:2.3! Extremely useful for close ups and great for flower shots

05-03-2009, 09:42 AM   #24
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QuoteOriginally posted by kthung Quote
Are those HDR?
No. I shoot RAW and use Photoshop Elements with ACR 4.4.1 to convert the files. After correcting distortions and CA I use USM 250/0,35 and USM 10/40. After that I use softlight 20%.

QuoteOriginally posted by kthung Quote
I have only used the sigma 17-70 and it is definitely the ideal vacation lens for me. One thing to add to consideration is that the sigma has a really close focusing distance (essentially as close as youre willing to put the front element to the subject) and a max magnification of 1:2.3! Extremely useful for close ups and great for flower shots
I had a DA50-20mm which I never used. I hate changing lenses. So the Sigma 17-70mm was my holiday lens. But 70mm is a bit short sometimes so I bought the DA18-250mm which is a very nice lens indeed. I also have a DA16-45mm and a DA12-24mm. I always felt that the colour rendition of the DA16-45mm was better tan that of the Sigma 17-70mm which I sold. The range 17-70mm is very nice so I bought a DA17-70mm when I was in the UK in March. The colour rendition is the DA17-70mm is very good indeed. As to sharpness, the Sigma 17-70mm and the DA17-70mm are equal, I would say. It is very personal which of the two is the better lens. As far as I am concenred the colour rendition of the Pentax lens is better.
05-03-2009, 11:05 AM   #26
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This isn't mandatory reading in my opinion. Brett comes to this conclusion:


"There is something wrong with both the DA17-70 and Sigma 17-70 that I have."

There is something wrong (versus - FA24-90): Pentax SLR Talk Forum: Digital Photography Review
05-03-2009, 05:59 PM   #27
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My subjective evaluation of the DA 17-70mm that I managed to try from my local Pentax agent versus the Sigma 17-70mm that I have is the Sigma has the edge in terms of sharpness, CA and light falloff at the corners.
I kinda like the colour rendition from the Pentax, much like the DA 16-45mm that I once had. Also the SDM is obviously quiet and the Quick Shift a plus. One thing to note is the Pentax lens barrel is much longer compared to the Sigma when extended, which is pretty noticeable. The Sigma can get lens creep (hasn't happened with mine yet) as reported by others who own the lens, but there is a lock on the barrel to take care of it. If I had a choice, the Sigma would be my obvious pick, especially the very useful close-up ability it has. Much as I like to go Pentax, the Sigma is the one with the better value proposition. I don't get hung up on MTF numbers because they don't reveal everything about a lens.

Last edited by creampuff; 05-03-2009 at 06:06 PM.
05-03-2009, 06:15 PM   #28
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QuoteOriginally posted by Hythloday Quote
This isn't mandatory reading in my opinion. Brett comes to this conclusion:


"There is something wrong with both the DA17-70 and Sigma 17-70 that I have."

There is something wrong (versus - FA24-90): Pentax SLR Talk Forum: Digital Photography Review
well, at least you made it to the end! i don't think anyone else has compared them directly like he has so it's still good to see
05-03-2009, 06:27 PM   #29
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QuoteOriginally posted by creampuff Quote
I don't get hung up on MTF numbers because they don't reveal everything about a lens.
They reveal resolution and debunk subjective claims that such and such a lens is sharper than the other based on who knows what--believing really is seeing, i.e., your brain can easily see/hear what it wants to:

Michael Shermer on strange beliefs | Video on TED.com

DA17-70 is sharper than the Sigma at f/4, at least, at some focal lengths, as long as you focus right and do the test right.
05-03-2009, 06:55 PM   #30
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QuoteOriginally posted by asdf Quote
They reveal resolution and debunk subjective claims that such and such a lens is sharper than the other based on who knows what--believing really is seeing, i.e., your brain can easily see/hear what it wants to:

Michael Shermer on strange beliefs | Video on TED.com

DA17-70 is sharper than the Sigma at f/4, at least, at some focal lengths, as long as you focus right and do the test right.
Given that you are a DA 17-70mm owner, I can understand you wanting to justify and claim that the Pentax has sharper resolution, etc. But please note that results of lens tests only pertain to that particular copy of the lens being tested. That's why I take such reviews only as a very rough guide because it is a stretch to make generalizations from a single instance and we all know there are always sample variations among lenses.

As I stated earlier, I base my opinion on actual photos that I had taken and in my estimation, the Sigma that I used had the edge over the Pentax I had from my local Pentax agent. I trust my eyes over some chart and results posted by some fella I don't know on the internet. And by the way, can your MTF charts describe colour rendering... how quick a lens focuses. I know my Sigma doesn't hunt as much if that's relevant... The Pentax is a fine lens imo but not demonstrably superior to the much cheaper and more compact Sigma. Subjective enough for you...
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