[Jonathan Mac]

I have read mixed reviews of the 20-40mm but it remains near the very top of my "wanted" list as I love the Limited primes and something with that focal range would suit most of what I do All I've read about the Sigma, before coming to this thread, is the problems in focusing, which when combined with the perhaps not class-leading AF from Pentax, puts me off. Personally I think the size, weight and limited zoom range are too high a price to pay to make a lens that fast. I prefer to switch to a prime if I need something faster than f/2.8 or f/4.

The Tamron 17-50/2.8 is a very good lens with impressive sharpness even wide open at all focal lengths - said the guy who got a good copy. I know many others didn't get so good a copy and have problems. In my case I only sold it when I got the Sigma equivalent, and you can read about the pros and cons of each in my review of the Sigma. For a lower price, less weight and a more useful focal range, I think 17-50mm is a better choice than 18-35mm. Yes, the Pentax also has only a 2x focal range, but it's not huge, is weather resistant and is a Limited lens.

[clickclick]

I do not have the Sigma, but I do have the 20-40, and I really like it. In typical Limited fashion, it handles and renders beautifully. I'll often grab it and my 15 Limited for the wider stuff and my 55-300 PLM for the far end. That makes a really sweet walkabout kit in my world with my K-3 II. I have several Sigma lenses, which I like, but I think I prefer the color rendering from my Pentax lenses. A little warmer feel. I'd check out sample photos from both lenses and see what you like:

Pentax Camera & Lens Sample Photo Search Engine - PentaxForums.com

Obviously, if you need absolute speed, the Sigma wins, but from what you write, that may not be that big of an issue. Would you like WR? Then a nudge to the 20-40.

[normhead]

The Tamron 17-50/2.8 is a very good lens with impressive sharpness even wide open at all focal lengths - said the guy who got a good copy.

Our copy is good but inconsistent. I tried to include it in test group one day and it simply wouldn't perform and I couldn't figure out why. The next day it was back to normal.

[AH11]

After long debate with myself, I am settling for the Pentax 20-40mm. I really wouldn't use the 18-24mm range at a wider than 2.8. Its just so much glass to carry around and it would surely give me lot more knots and upper back pain (issue that I have when continuously holding heavy stuff). Unfortunately, my favorite lens, the fa 43mm has the focus ring jammed. I will either have to send it for repairs or sell as is and may end up with the HD 40mm f2.8 one day. Focusing issue is another factor as I had a hard time dealing with my Tamron 17-50mm front/back focusing. Pentax 20-40mm image quality based on sharpness and contrast seems top notch from what I have read between f5.6 to f8 and hopefully has good color rendition.

[normhead]

After long debate with myself, I am settling for the Pentax 20-40mm. I really wouldn't use the 18-24mm range at a wider than 2.8. Its just so much glass to carry around and it would surely give me lot more knots and upper back pain (issue that I have when continuously holding heavy stuff). Unfortunately, my favorite lens, the fa 43mm has the focus ring jammed. I will either have to send it for repairs or sell as is and may end up with the HD 40mm f2.8 one day. Focusing issue is another factor as I had a hard time dealing with my Tamron 17-50mm front/back focusing. Pentax 20-40mm image quality based on sharpness and contrast seems top notch from what I have read between f5.6 to f8 and hopefully has good color rendition.

My wife has a Tamron 17-50 and we've had the same inconsistency issues. I'd love to buy her one. With the new DFA 21 ltd. and the K-new coming, it may take a while to get to it.

[Gene D]

I have read mixed reviews of the 20-40mm but it remains near the very top of my "wanted" list as I love the Limited primes and something with that focal range would suit most of what I do All I've read about the Sigma, before coming to this thread, is the problems in focusing, which when combined with the perhaps not class-leading AF from Pentax, puts me off. Personally I think the size, weight and limited zoom range are too high a price to pay to make a lens that fast. I prefer to switch to a prime if I need something faster than f/2.8 or f/4.

The Tamron 17-50/2.8 is a very good lens with impressive sharpness even wide open at all focal lengths - said the guy who got a good copy. I know many others didn't get so good a copy and have problems. In my case I only sold it when I got the Sigma equivalent, and you can read about the pros and cons of each in my review of the Sigma. For a lower price, less weight and a more useful focal range, I think 17-50mm is a better choice than 18-35mm. Yes, the Pentax also has only a 2x focal range, but it's not huge, is weather resistant and is a Limited lens.

I have both the 20-40mm and the Sigma 17-50mm F2.8 EX DC HSM, that has been mentioned by a few here. I purchased the 17-50 first and really love its sharpness and range, and at f2.8 all I need in a zoom for that range. Think it is worth looking at as well--great reviews on this site as well. Took it to Europe for travel and hiking. Pro's were the sharpness, flexibility, great in good weather (used hood in some nasty rain and worked fine) . I think I learned how to work with zooms on this camera. It may be a bit heavy but have done a few long mileage hikes and with a sling pack not too bad. Then, purchased the 20-40 for another trip to London and very rainy weather this past fall and early winter. Pro's were portability, handling, weather resistance, and the color rendition--feels less clinical as some have mentioned, maybe not as sharp but the colors were different and more vibrant. I also felt like I would work with the colors as a starting point better in Lightroom. They both really are different and solid in their own way. In the end maybe worth borrowing if you can to test them. I have struggled with getting rid of one, but in the end love both .

[mikesbike]

I have both the 20-40mm and the Sigma 17-50mm F2.8 EX DC HSM, that has been mentioned by a few here. I purchased the 17-50 first and really love its sharpness and range, and at f2.8 all I need in a zoom for that range. Think it is worth looking at as well--great reviews on this site as well. Took it to Europe for travel and hiking. Pro's were the sharpness, flexibility, great in good weather (used hood in some nasty rain and worked fine) . I think I learned how to work with zooms on this camera. It may be a bit heavy but have done a few long mileage hikes and with a sling pack not too bad. Then, purchased the 20-40 for another trip to London and very rainy weather this past fall and early winter. Pro's were portability, handling, weather resistance, and the color rendition--feels less clinical as some have mentioned, maybe not as sharp but the colors were different and more vibrant. I also felt like I would work with the colors as a starting point better in Lightroom. They both really are different and solid in their own way. In the end maybe worth borrowing if you can to test them. I have struggled with getting rid of one, but in the end love both .

I have the same combo, and love it. Boils down to when do I need the faster aperture for low light, etc. and when do I need the above advantages of the DA 20-40mm Limited- especially nice on my KP! The very modest price of the Sigma lens together with a good deal on a new 20-40 LTD made the combo an attractive decision for me.

[UncleVanya]

I use my 20-40 with my 50-135 as a light carry kit with some serious chops.

[PocketPixels]

I don't understand the concern with lens flare if you're considering purchasing a wide-angle ƒ/1.8 lens. A lens like that is for interior in low light, astrophotography, or night landscapes. Not much chance of lens flare in any of those circumstances. Will you be doing many ƒ/1.8 landscapes into the afternoon sun? What do you see yourself photographing, to the extent you can predict such things?

I own three Limited lenses (HD 15mm, SMC 21mm, SMC 70mm) and their resistance (inability?) to flare is one of the hallmarks of the Limited series. None of them are my sharpest lenses. though. Sharp enough, sure. But the Limited lenses seem to be about color, flare-resistance, small size, and delightful build quality.

I own a Sigma 17–50mm ƒ/2.8, and the build quality and sharpness are superb. The HSM auto focusing is wonderful, with the modest annoyance of having to flick TWO switches to "manual" before i can adjust focus. I expect the fit and finish, the tactile "delight" of the Sigma Art lens will be very close to the Limited. My Sigma is very heavy on my K-S2, the 18–35 weighs a good bit more, and I can only imagine how heavy the 18–35 will feel after even a modest stroll through town.

Thanks for all the feedback. I am still debating. Image sharpness is important to me overall and I guess the Sigma, based on what I have researched, is the clear winner by far, right? But it sure is heavy and flare can be a major drawback. I suppose I can live with the flare and just have to adapt. Plus the Pentax at 40mm can only go to f4. But I can also live with that. Just have to change to my prime lenses when in need of f2.8 or lower.

[swanlefitte]

Did someone say sigma lens flare? was worried about my sensor with this one.


eeking out low light? f/1.8 1/90 3200


need every bit of rust shown?


If not the 20-40 will do it smaller, lighter, in the rain and will probably be with you where the sigma won't.

[Austro-Diesel]

I owned the Sigma 18-35/1.8 | Art for a few months. Impressive sharpness, AF was okay on K-5 IIs and K-3, a bit bulky and heavy. The background bokeh was often "busy", when structured smaller things like leafs were only a bit blurred. You see onion-type rings on each light circle, depending on focal length, blurring, local contrast. A special lens in my eyes.

For example the Sigma 35/1.4 | Art is fully different. Smooth bokeh in every situation.

[AH11]

Thanks for all the feedbacks. I actually ended up purchasing the Sigma 17-50mm and I am overall pleased with the photo results except certain flares. The 18-35mm f1.8 art lens was just going to be a little too heavy. One day, I may invest in buying the Sigma art 35mm lens as it gets very high praises.
I decided to put the Sigma lens to test and it hasn't disappointed me except the autofocus. It has major back/front focusing issues which can be partly adjusted from the camera but it doesn't focus properly every time. Different focal lengths end up focusing in different planes slightly and it is frustrating. I would need to take at least 2-3 photos to have one of them in good focus, very disappointing.
I have tested it vs my Tamron 17-50mm f2.8 (which I have sold now), Pentax 12-24mm f4, Pentax 35mm f2.4 and Pentax 50mm f1.4 using water bottles as test objects. I am very pleased with the sharpness and contrast results overall (just did the testing at f2.8 and f5.6).
In the water bottle tests it does a better job than my Pentax 50mm f1.4, surprisingly, and was also at par with the 35mm f2.4 prime lens.
You can judge for yourself. The Tamron doesn't match up except wide open at 17mm (Sigma focused slightly back). Pentax 12-24mm was tested at 17mm f5.6 and had excellent results.
Flaring may be a subjective matter depending on the type. Most flaring with this Sigma lens will not be pleasant except few I took before sunset.
All family photos taken with the Sigma in order of following:
50mm @ f4, 19mm f11, 22mm f5.6, 31mm f5.6, 36mm f4, 50mm f5.6

[AH11]

another flaring example 31mm f5.6

[normhead]

Thanks for all the feedbacks. I actually ended up purchasing the Sigma 17-50mm and I am overall pleased with the photo results except certain flares. The 18-35mm f1.8 art lens was just going to be a little too heavy. One day, I may invest in buying the Sigma art 35mm lens as it gets very high praises.
I decided to put the Sigma lens to test and it hasn't disappointed me except the autofocus. It has major back/front focusing issues which can be partly adjusted from the camera but it doesn't focus properly every time. Different focal lengths end up focusing in different planes slightly and it is frustrating. I would need to take at least 2-3 photos to have one of them in good focus, very disappointing.
I have tested it vs my Tamron 17-50mm f2.8 (which I have sold now), Pentax 12-24mm f4, Pentax 35mm f2.4 and Pentax 50mm f1.4 using water bottles as test objects. I am very pleased with the sharpness and contrast results overall (just did the testing at f2.8 and f5.6).
In the water bottle tests it does a better job than my Pentax 50mm f1.4, surprisingly, and was also at par with the 35mm f2.4 prime lens.
You can judge for yourself. The Tamron doesn't match up except wide open at 17mm (Sigma focused slightly back). Pentax 12-24mm was tested at 17mm f5.6 and had excellent results.
Flaring may be a subjective matter depending on the type. Most flaring with this Sigma lens will not be pleasant except few I took before sunset.
All family photos taken with the Sigma in order of following:
50mm @ f4, 19mm f11, 22mm f5.6, 31mm f5.6, 36mm f4, 50mm f5.6

You did a lot of work. Info like that is hard to come buy... and really, it's the only info that counts. A test chart can tell you what the test scores are, but that doesn't necessarily correlate to which lens you like. You always have to do the work if you want to be sure. When last tested, my Tamron 17-50 did much better than yours. Now you run into the problem of sample variation as it relates to anything beyond your two lenses. My Tamron 17-50 gives mixed results. When it's on it's better than what you've posted, when it's not it's about the same. The one lens produces different results different days. What scares me about the Tamron is the inconsistency. I don't know whether the lens is having a good day or a bad day when I'm shooting.