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09-09-2019, 04:41 PM   #1
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Sigma 17-50mm F2.8 EX DC HSM ?

I looked at the reviews and a handful of pics from this lens. I have a question: Does this lens exhibit barrel distortion at 17mm? It appeared that a few of the pics I viewed display significant distortion @17mm, maybe it's just me? How many people own and shoot with this lens regularly? I would like your thoughts.

09-09-2019, 04:50 PM - 1 Like   #2
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OpticalLimit reviewed the lens (Sigma AF 17-50mm f/2.8 EX DC HSM OS - Review / Test Report) and reported ~3% distortion at 17 mm. That is not too large and can best corrected by softwares (eg PTLens software).

Hope that the info may help.

Last edited by hcc; 09-09-2019 at 09:21 PM.
09-09-2019, 05:01 PM - 1 Like   #3
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The Sigma 17-50 was my favorite and most-used lens for years before I switched to FF. In my opinion I think the distortion is minimal and was never a concern for my shots. I don't think I corrected the distortion more than just a couple of times over the years. Of course my shooting was more landscape than something more revealing like architecture, but I did take urban shots and still didn't see the need for correction.
09-09-2019, 07:09 PM - 1 Like   #4
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Hi:

I just purchased this lens (arrived today).

I have a K1 and most of my lenses are full frame.

I shoot mostly fitness, BJJ, and MMA and use the K1 for this most of the time.

I also have a K3 and K5ii and sometimes like to have a smaller camera with me and did not have an aps-c zoom.

Given the current price I picked up the Sigma 17-50.

I used to own it in the past, but sold it as I moved to full frame.

I just started playing with the lens (it arrived today).

I will play with the lens some more over the week and this weekend.

Are there any pictures you'd like me to take at 17 mm?

I live in (somewhat rural) Maine. I am not too far from the capital and am happy to take some pictures of the capital and a few statehouse buildings which should provide you with examples of distortion.

I can upload to Dropbox the RAW files.

09-09-2019, 09:24 PM - 1 Like   #5
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One of my favorit lenses. I use it on my K-70, and itís my favorit walk around lens. I think build quality is very good, and itís one of the sharpest lenses that i got.
Fishing Boats | Karsten Peltonen | Flickr
09-10-2019, 03:46 AM   #6
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QuoteOriginally posted by candgpics Quote
Hi:

I just purchased this lens (arrived today).

I have a K1 and most of my lenses are full frame.

I shoot mostly fitness, BJJ, and MMA and use the K1 for this most of the time.

I also have a K3 and K5ii and sometimes like to have a smaller camera with me and did not have an aps-c zoom.

Given the current price I picked up the Sigma 17-50.

I used to own it in the past, but sold it as I moved to full frame.

I just started playing with the lens (it arrived today).

I will play with the lens some more over the week and this weekend.

Are there any pictures you'd like me to take at 17 mm?

I live in (somewhat rural) Maine. I am not too far from the capital and am happy to take some pictures of the capital and a few statehouse buildings which should provide you with examples of distortion.

I can upload to Dropbox the RAW files.
The photo's I have seen that seem to exhibit distortion are city street architecture. I'm not sure of your location, but if you could pop off a few like that, it would be great.
09-10-2019, 04:04 AM   #7
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Most of the time noticeable distortion in the 17mm lenses is because the camera was not level. Even my Tamron 10-24 exhibits lower distortion when I am on top of the camera being level.
09-10-2019, 05:06 AM   #8
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All wide angles have a bit of distortion. Zoom more so than primes (there are exceptions).
Usually easy to correct in post.
If you shoot jpeg, get a Pentax lens instead of the Sigma and get the in-camera correction.

09-10-2019, 05:56 AM - 1 Like   #9
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QuoteOriginally posted by kevinWE Quote
The photo's I have seen that seem to exhibit distortion are city street architecture. I'm not sure of your location, but if you could pop off a few like that, it would be great.
I live right near the downtown. Not exactly a large city, but I think I know what you're looking for.

I'm happy to take some pictures for you so you can get a sense of the distortion at 17 mm. Of course, there's always going to be some barrel distortion, as others have noted, with wide angle zooms and if you correct for it through software you'll typically lose a little bit of the width or you'll end up stretching the sides. So, it depends upon what you're comfortable with.

I use Capture One Pro for my raw conversions, although occasionally I'll use DXO Photolab or Adobe Camera Raw.

I typically find that I correct for barrel distortion very little, although to be fair, I tend not to shoot shoot very wide all that often.

I find that the lens profiles in software for wide-angle primes and zooms corrects the wide-angle by stretching things too much. Instead, I will manually correct for the distortion to taste.
09-10-2019, 04:37 PM   #10
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QuoteOriginally posted by ChristianRock Quote
All wide angles have a bit of distortion. Zoom more so than primes (there are exceptions).
Usually easy to correct in post.
If you shoot jpeg, get a Pentax lens instead of the Sigma and get the in-camera correction.
I never shoot jpeg
09-10-2019, 07:18 PM   #11
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QuoteOriginally posted by kevinWE Quote
I never shoot jpeg
Well that's easy then. Any good Raw developer will have a profile for this lens.
09-11-2019, 01:04 PM   #12
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All wide angle to telephoto zoom lenses will exhibit some degree of visible distortion especially at the widest FL. Usually barrel distortion here. The degree of distortion at 17mm by this Sigma lens is easily less than most such lenses. By 24mm it is very low. If you are looking for a fast-aperture f/2.8 zoom lens, this is one sharp baby. The downside is- no WR. The much more expensive Pentax DA* 16-50mm f/2.8 exhibits comparatively more distortion, but you get WR construction. Downside is also a substantial chance of its SDM motor to fail.

For low distortion architectural wide angle shots, I turn to the Sigma lens's vey fine cousin, the Sigma 10-20mm f/3.5 EX DC. At the hugely wide angle of 10mm, distortion is substantial, but actually less than the 17-50mm lens at 17mm!! Amazing for being at 10mm. At 15mm, however, it is basically free of distortion altogether.

The Pentax DA 12-24mm f/4 exhibits lower than average distortion at 12mm, but still visible. It is virtually distortion-free at 24mm. 24mm on APS-C is not real wide but still wide angle, and since linear distortion-free, that would be good for single building architectural shots, because at this more modest wide angle, perspective distortion will not be as bad. Perspective distortion is unavoidable in WA lenses. It is the kind of distortion that causes vertical subjects to lean in from the sides or backwards from the center, and gets worse the wider the FL, but better the more distant the subjects. This Pentax lens sells now new at around $700.

The Sigma 10-20mm f/3.5 EX DC, however, is currently offered at B&H for an amazingly reduced price. I recently bought one. It is a very nice, well-designed, fine-performing lens.

Last edited by mikesbike; 09-11-2019 at 01:31 PM.
09-12-2019, 07:09 AM   #13
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QuoteOriginally posted by mikesbike Quote
All wide angle to telephoto zoom lenses will exhibit some degree of visible distortion especially at the widest FL. Usually barrel distortion here. The degree of distortion at 17mm by this Sigma lens is easily less than most such lenses. By 24mm it is very low. If you are looking for a fast-aperture f/2.8 zoom lens, this is one sharp baby. The downside is- no WR. The much more expensive Pentax DA* 16-50mm f/2.8 exhibits comparatively more distortion, but you get WR construction. Downside is also a substantial chance of its SDM motor to fail.

For low distortion architectural wide angle shots, I turn to the Sigma lens's vey fine cousin, the Sigma 10-20mm f/3.5 EX DC. At the hugely wide angle of 10mm, distortion is substantial, but actually less than the 17-50mm lens at 17mm!! Amazing for being at 10mm. At 15mm, however, it is basically free of distortion altogether.

The Pentax DA 12-24mm f/4 exhibits lower than average distortion at 12mm, but still visible. It is virtually distortion-free at 24mm. 24mm on APS-C is not real wide but still wide angle, and since linear distortion-free, that would be good for single building architectural shots, because at this more modest wide angle, perspective distortion will not be as bad. Perspective distortion is unavoidable in WA lenses. It is the kind of distortion that causes vertical subjects to lean in from the sides or backwards from the center, and gets worse the wider the FL, but better the more distant the subjects. This Pentax lens sells now new at around $700.

The Sigma 10-20mm f/3.5 EX DC, however, is currently offered at B&H for an amazingly reduced price. I recently bought one. It is a very nice, well-designed, fine-performing lens.
The Sigma 10-20mm does seem like a great deal right now, it's not even worth looking at used copies when they are selling for 329 new! The DA 12-24 is also a fine lens capable of great pictures, and the new DA*11-18mm f/2.8 is supposed to be a gem!

But I think the OP is looking for a more general-purpose lens, a wide-to-short-tele fast zoom.

Regarding the Pentax DA*16-50mm f/2.8... I think you mention it's expensive and has a high chance of SDM fail. But it's expensive if you buy a new copy - and new copies, from what I gather, have a redesigned SDM motor and are not as likely to fail. If you buy an older used one that has a high chance to fail, you're looking at 300-400 dollars in the used market, at which point the lens becomes a good deal for what it is. And for that price you can get one that has been converted to screw-drive AF - a bit noisy yes, but reportedly the AF is faster, and is very unlikely to fail. So it is an alternative. There's pros and cons of it vs. the Sigma 17-50:
-Sigma a bit better optically but Pentax (to my eyes and to a few people here in the forums) better colors and overall rendering
-Pentax is WR, Sigma isn't
-Neither is very flare resistant, Tamron 17-50 is better in this regard - but Tamron has its own shortcomings, such as build quality not being what you'd expect from a pro-oriented 17-50 2.8 lens. But optically it's a fine lens and cheapest of the bunch.

Luckily, this forum has done a nice comparison of all 3 so hopefully that can make the OP's decision easier: Pentax 16-50 vs Sigma 17-50 vs Tamron 17-50mm - Review Announcements | PentaxForums.com

Lastly, a couple of dark horsse, including the lens that I use... the older DA 16-45mm f/4 (I have that) and the DA 17-70mm f/4. Either one of these lenses can be had for very cheap (and there's still new copies of the DA 17-70 around for under 200 dollars!). Used, either one can be had for close to and sometimes under 100 dollars. The reason I went for the DA 16-45 is because I liked the rendering a bit more (most people prefer the DA 17-70 though in that regard, but the truth is either one can take nice images). Also, the DA 17-70 can't be converted to screw drive like the DA* 16-50 can - so if the motor fails, the lens is basically lost. So these would not be the most popular choices in this day and age, and copies of the DA 16-45 and DA 17-70 can be bad or decentered (like any other lens, including the f/2.8 zooms we talked about). But if you find a good copy they can do a good job, and the upside is that they'll be lighter to carry around in hikes and nature walks than the f/2.8 counterparts. I just thought I'd mention them
09-12-2019, 01:39 PM - 1 Like   #14
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A good overview of these lenses, Christian. I am still leery of the DA* 16-50mm f/2.8 even though it is said the SDM motor has been upgraded. But you do get WR, although I have that covered with my DA 18-135mm. Ages ago, Pop Photo magazine released a teat review, where they measured the actual longest FL closer to 45mm than 50mm. Then there is the cost factor. I've been happy with the colors and rendering with the Sigma.

In another thread here by mhsp 1948, who has quite a lot of top-end Pentax gear, he recently bought the Sigma 17-50mm f/2.8 EX DC HSM for his KP and has been very happy with it, as shown in his thread.

I brought up the Sigma 10-20mm f/3.5 because Kevin expressed a concern regarding linear distortion at the wide angle setting which would be visible in cityscape shots having buildings, etc. Of course a wide angle only zoom lens does not replace a WA-to-tele versatile zoom lens, but would serve to extend range and could eliminate linear distortion for wide angle shots.

Perspective distortion is greatly reduced or near eliminated with wide angle shots when taken at a greater distance form the subject matter, as in cityscapes. It gets worse the closer one gets to subjects.

Last edited by mikesbike; 09-12-2019 at 01:56 PM.
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