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06-17-2013, 11:55 PM   #1
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Sigma DC 17-70mm f/2.8-4.5 vs Pentax-DA 18-135mm F3.5-5.6

Has anyone compared the above two lenses in terms of image quality? I have had the Sigma for quite some time and find it fast, sharp and Ok as an indoor lens but it's not as long as I would like when going out. Now I am going to move to Maine and I know I will do a lot of fishing and my K-30 will be tagged with me along beaches and rivers. That make me think about WR of the Pentax 18-135, but right now I am in a tight budget and can not afford to buy the Pentax, so put me into the idea of selling the Sigma and may be a flash to fund for the Pentax. But before I do it I need to know the IQ of the Pentax can match the Sigma or not (I understand there are differences in focal length and fastness of the two). So anyone has owned or used both of them, please give me your opinion about their IQ .
Thanks in advance

06-18-2013, 12:26 AM - 1 Like   #2
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I've also been thinking this lens would be Ideal, but not so sure now after reading review here ( Pentax K Lens Tests ) both the Sigma and the Pentax lens reviewed here by the same people using the same methods etc. Hope this helps
cheers
06-18-2013, 02:17 AM - 1 Like   #3
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I replaced the Sigma 17-70 with the 18-135. It was a good move on my part.

I don't take photos of brick walls, I don't pixel-peep, I don't read measurebator reviews, and I don't painstakingly compare in great detail one lens to another at every focal length/aperture combination.

The Sigma 17-70 is a fine lens, but I much prefer the 18-135 for its versatility, coloring rendering, and other non-quantifiable qualities.
06-18-2013, 02:31 AM - 1 Like   #4
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K-01 with 18-135WR

I also had reservations about the 18-135 after reading the Photozone test.
But when I saw samples and reviews of photographers on this forum (and the other forum), I decided to take a plunge and got one some 4 months ago.
Have been pleasantly surprised by the IQ. It is not quite prime quality especially wide open, but stepped down alittle gives great results.
Here are some samples:

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06-18-2013, 05:31 AM - 1 Like   #5
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I own the Sigma and extensively used a friend's 18-135. The latter is fine by itself, with a flexible focal length, WR and SDM. However, even without pixel peeping, the Sigma is a better lens optically. For me the difference is obvious. It's faster, quite sharper in the corners, a bit sharper in the center, with a bit more contrast (that last item is subjective).

I also do a lot of outdoors activities. My solution is to use the 18-55 WR when conditions are more difficult, bringing along the 100 macro WR if needed (and now I also have the bulkier 60-250 ) It would be an economical (and even more compact) solution for you, allowing you to keep the Sigma.
06-18-2013, 06:03 AM   #6
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QuoteOriginally posted by MPrince Quote
I replaced the Sigma 17-70 with the 18-135. It was a good move on my part.

I don't take photos of brick walls, I don't pixel-peep, I don't read measurebator reviews, and I don't painstakingly compare in great detail one lens to another at every focal length/aperture combination.

The Sigma 17-70 is a fine lens, but I much prefer the 18-135 for its versatility, coloring rendering, and other non-quantifiable qualities.
I don't do any of that either, ... well I do read reviews, and I don't think I would be complaining too much if I had the lens, but the comments from someone who's job it is to test lenses and who obviously has seen and used a lot of lenses should not be dismissed as a "measurebator review", I think they certainly deserve consideration and I would put more weight on those comments than the totally biased comments in favor of all things Pentax you see on this forum, which is expected of course being a Pentax Forum. Don't get me wrong, I'm a Pentax fan, have been since my days with the Spotmatic F, I like the 18-135 and thought it to be my ideal general purpose lens, just not so sure now, still considering whether to add it to my must have list.
cheers.
06-18-2013, 08:49 AM   #7
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QuoteOriginally posted by Cee Cee Quote
...the comments from someone who's job it is to test lenses and who obviously has seen and used a lot of lenses should not be dismissed as a "measurebator review"...
My comment was not directed at any specific individual or website. Sorry you took it that way.
06-18-2013, 10:37 AM - 1 Like   #8
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I had the Pentax 18-135 and was not impressed by the IQ at the long end. I traded it for the DA* 50-135. I'm a happy camper now. I think if you can get the 18-135 for $350 or less it would be worth it. More than that forget it.

06-18-2013, 05:55 PM   #9
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QuoteOriginally posted by MPrince Quote
My comment was not directed at any specific individual or website. Sorry you took it that way.
all good , I never took any offense at anything you said, we just see things a little differently, that's cool.
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06-18-2013, 06:15 PM - 1 Like   #10
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I own both and also believe the Sigma to be better IQ in general than the Pentax. That said, I love the Pentax and is probably the best all-purpose consumer level zoom I've used. The WR is great for peace of mind, and as for IQ, I do think the colour rendition is a little better than the Sigma - something easily fixed in PP. However it is not as sharp, not as fast and displays less contrast.

The biggest weakness of the Pentax lens is at the longer end, which of course defeats the purpose of replacing the Sigma. Rather than give you advice, I will tell you my lens plan. When I have some more funds, I intend to sell my 18-135 (and some others) to fund a 60-250 f/2.8 and keep the Sigma 17-70.

Edit: That said, some of my best images were taken with the 18-135 because it's a lot more versatile and so happened to be on at the right time. In my mind, that speaks a lot in itself.

Last edited by Adinfinitum; 06-18-2013 at 06:21 PM.
06-18-2013, 06:23 PM   #11
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Original Poster
Thank you everyone for your inputs. Looks like if I want to get the Pentax 18-135 then I have to find another way to get the fund but not by selling the Sigma 17-70, so I can have both of them and then compare and make decision later.
Again, thanks all of your time on this topic.
06-19-2013, 05:52 AM   #12
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QuoteOriginally posted by Adinfinitum Quote
However it is not as sharp, not as fast and displays less contrast.
True. I shot some portraits with the Pentax this weekend (it was loaned to me, my Sigma is out for repairs) and I noticed the difference without any on-screen zoom.

QuoteOriginally posted by Adinfinitum Quote
fund a 60-250 f/2.8 and keep the Sigma 17-70.
The 60-250 is a worthy companion to the Sigma, in fact it's much better still. The 18-55 WR kit, 60-250 and 100 macro WR make for a killer WR combo.
06-19-2013, 09:12 AM   #13
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I have both but I've only had the 18-135WR for about two weeks now so I can't definitively say it's the better of the two yet. I did take some pictures from the same focal length but different aperture due to the Sigma going to 2.8 and Pentax 3.5 at the wide end. I noticed a lot more barrel distortion and loss of contrast in the Pentax at the wide end (18mm). Pictures look better with Pentax from 20-35mm range and in my opinion the Sigma looked better from 50-70mm. At 70mm where they were both at f4.5. The Sigma is noticeably louder and slower to focus than the Pentax indoors and outdoors The Pentax is lightning quick and really quiet.

So now I'm in my limited time with the lens I actually like the Sigma better if I were doing wide angle shots and maybe just maybe the Pentax for group events. This all could be due to me having a lot more time with the Sigma (1 years). If I had the money right now I would sell the Pentax, keep the Sigma and get the Pentax 50-135 f2.8 and consider it a done deal.
11-11-2013, 11:52 AM   #14
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I've been interested in both the Pentax 18-135WR and Sigma 17-70mm f/2.8-4 myself.
My primary rationale around the Pentax lens was 2 fold:

1. WR
2. Longer range

My primary rationale around the Sigma was:

1. Faster lens (I do enough indoors )
2. Macro abilities
3. Image quality.

I'll probably lean towards the Sigma due to the fact that I do have a long(er) cheap Sigma 18-200mm DC which covers the long end. In the long term, I'll probably replace it with a Pentax 55-300mm WR and have a decent pair to go along with my Rokinon 85 f/1.4 manual.
Outdoors - I don't need the fastest/heaviest lens - but would like something decent. Indoors / short range, I'd like something faster - this should provide what I'm looking for - with a little overlap.
02-03-2014, 09:09 PM   #15
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Yes, I'm reviving a thread that's a few months old, but I'm finding myself in a similar position. I have the DA 18-135. I really like it. I especially love the range and the WR. I really don't see any reason not to keep it as a great, all-purpose walkaround.
But...
About 75% of my photos are in the 18-70 range, about 10% in the 10-20 where I use a Sigma, 10% in the 70-135 range where I use either the 18-135 or my DAL 55-300 which also covers the rest of the long end.
So I'm trying to decide if one of the 17-70s (for now, either the 1st Sigma for which a used copy goes for around $225 or the latest Sigma Contemporary for about double that amount) would give me that little extra sharpness, especially around the edges at the wide end.
So, if others have had both since when this thread was started, I'd be interested to hear your opinions about the two lenses.
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