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Sigma 17-50 lens looks to be decentered... or not?


pmndaniel 1 7
21 Jun 2017 11:13AM
Hey everyone!

I'm totally new to this place so please bear with me if I post in the wrong thread. Long story short, I seem to have an issue with my Sigma lens.

I will post the first image, the one that seems to be more blurred on the left side than on the right side. Used f/8 at 17mm, focus in the center, staying perpendicularly in front of the wall. The image has not been edited in any way and I wasn't really looking to get a nice picture at all. Here it is:

307007_1498039890.jpg



The second one, at f/8 and 50mm. Look how soft the left side becomes while the right is perfectly sharp. This was taken handheld but the shutter is 1/500s so should be absolutely no issues:

307007_1498039929.jpg



And now, the final image, taken using a tripod and placing it in front of the wall, with some math formulas in focus. Both center-focused, the first one at f/2.8:

307007_1498039966.jpg



and the second one at f/8:

307007_1498039987.jpg



That's the confusion. The last two shots look sharp and the blur looks evenly distributed across the two sides. Or am I fooled by the lack of light on the edges?

Is my lens defective in any way? 'Cause I do have other examples with the left side being more blurry than the right one. It's been calibrated with the body (a Nikon D5300 by the way), or at least that's my local repair shop states.

Thanks so much for your time, greatly appreciated.

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pmndaniel 1 7
21 Jun 2017 11:16AM
There is no chance for you to see what I am talking about with a highly compressed image and, at the same time, there is no chance for me to add links to high-resolution images since I am getting the 'your message has been marked as spam' error (probably because I'm new to the website).

Well, I guess that's my first experience with ephotozine. Hello everyone Smile
Philh04 Plus
13 2.0k United Kingdom
21 Jun 2017 12:04PM
As you say, hard to tell from the posted images, perhaps you can post crops of the left, centre and right of the image, might be easier to see... it is fairly normal for a lens to be softer towards the edges but at f8 one would expect that to have been 'cured'.

How old is the lens? Has it had a knock at any time?

Phil
pmndaniel 1 7
21 Jun 2017 12:35PM
pmndaniel 1 7
21 Jun 2017 12:36PM
It looks like it's working one by one. Let me post all the images and I'll get back to you.
pmndaniel 1 7
21 Jun 2017 12:40PM
http://extrazoom.com/image-87608.html

http://extrazoom.com/image-87607.html

http://extrazoom.com/image-87611.html

http://extrazoom.com/image-87610.html

The lens is quite new, less than 6 months old. I usually wear the hood while shooting and yes, it might have got a gentle knock in crowded places but whatever wanted to hit the lens, it hit the hood first. It has not been dropped, that's absolutely sure. Please let me know if you can see the images now.

Thanks Phil, really appreciate it!
Philh04 Plus
13 2.0k United Kingdom
21 Jun 2017 1:09PM
Yes can certainly see a lot better now... to my eyes and enlarging the images I can see a very slight softening in the corners which may be inherent in the lens, I have no experience with this lens, but what I am seeing is maybe what I would expect. Have you had a look at any independent tests of this lens?

Seeing as the lens is less than 6 months old it is still covered by warrantee so if you are concerned you can always send it to Sigma with examples of your worries, my experience with Sigma is that the service is pretty good (others may disagree mind).

Phil
themak 5 1.0k Scotland
21 Jun 2017 1:10PM
Having owned this lens, I'd say the results are typical and well within bounds of acceptability. As you say, slightly worse on the left.
pmndaniel 1 7
21 Jun 2017 2:03PM
Thanks for your replies!

It just came back from warranty, that's what I am concerned of. They said it was 'calibrated and re-softed' and that the issue was 'front and back focusing'. Indeed it looks a bit better from what it was when I sent it to the repair shop but it's still not fixed as you can see. That's why I tend to believe there is something wrong with the lens.

Plus, I am leaving on holiday at the beginning of next week and I'd like to have my camera in the best shape, you know. What do you think, would it make sense to rent another Sigma and see if that behaves the same? If so, could I choose 17-70 in terms of sharpness or that's equally sharp?

Thanks again!
themak 5 1.0k Scotland
21 Jun 2017 2:43PM
If you rent, why not get the Canon (guessing) equivalent? You may then get an idea of how the Sigma is in comparison - I don't see much wrong with what you're getting. As for the 17-70, I haven't used it, but it's a fair bit older design.
Philh04 Plus
13 2.0k United Kingdom
21 Jun 2017 3:05PM
Indeed 17-70 is an older design...

The OP is using a Nikon, not sure really if Nikon has an equivalent apart from the very expensive 17-55mm f2.8 G DX AF-S IF-ED Lens.
pmndaniel 1 7
21 Jun 2017 3:08PM
Does anyone have any experience with Nikon's 16-80mm 2.8-4 in comparison with Sigma's 17-50?
I'm particularly interested in terms of sharpness., is it sharper than 17-50 overall?

I am willing to give up on my Sigma due to the multiple compatibility issues it has with my D5300 (yeah, those bugs are just annoying) and for the fact that I am looking to buy an all-around lens for traveling; it seems 16-80 has what I want in terms of zooming capacity and weight.

Any feedback is appreciated.
themak 5 1.0k Scotland
21 Jun 2017 3:18PM
I had the Nikon 16-85 at the same time as the Sigma 17-50 - Sigma sharper and distorts less. You'd expect the 16-80 to be an improvement as it replaced the 16-85. The rendition of the Nikon lens is quite a bit different - subjectively preferable for me.
Philh04 Plus
13 2.0k United Kingdom
21 Jun 2017 3:24PM

Quote:Does anyone have any experience with Nikon's 16-80mm 2.8-4 in comparison with Sigma's 17-50?
I'm particularly interested in terms of sharpness., is it sharper than 17-50 overall?


I'm afraid I can't help here as I am Canon based, it does look to be a good all round travel/walkaround lens if a little on the expensive side.

Good luck.

Phil
pmndaniel 1 7
21 Jun 2017 3:25PM
Thanks themak, would you recommend buying 16-80 then as a longer-term investment for my trips?
I found it in a local shop where I can test it, but I want to seek for a few opinions first.


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