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Brian's Photo Blog — Article 99
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Sony vs. Sigma Wide-Angle Lens Shootout
Sunday 20 May 2012   —   Category: Equipment
Back at the beginning of April I wrote about the Sigma wide-angle lens I had just purchased to possibly replace my existing Sony wide-angle lens. If you have not read that article yet, you should do so before you read this article, so you can understand why I’m even considering making this switch. There’s a lot to like about the Sigma 10-​20​mm f/3.5 lens over the Sony 11-​18​mm f/4.5-5.6, but in the end, image quality is going to outweigh any other benefits.

As I wrote back in April, I had not had a chance to actually take the Sigma lens on any photo outings due to the never-ending Oregon rainy season. But since then I have been able to take photos with the Sigma on two major outings. Vignetting has not been as big of a problem as I had feared, so in that respect I’m perfectly happy with the Sigma. On the other hand, I have been noticing some issues with image sharpness, which seems to get worse the farther you get from the center of the image.

Here are two 100%-magnification sections of a photo I took recently. The first section is from the center of the image. While not perfectly sharp, it is acceptable, and can even be improved. The second section, taken from the upper-left corner of the image, show a dramatic loss of sharpness, plus an increase in chromatic aberration. Even at lower resolutions, one can notice a lack of sharpness of the edges of some of my photos.


This lack of image quality with the Sigma lens makes me very unhappy. The question that came to mind was this: Does the Sony lens do the same thing, and I've just never noticed? Or is the Sony lens sharper at the edges? Which lens should I keep, and which should I sell? I've NOT been taking the two lens out together to shoot the same images at the same time, so I really was not able to answer these questions satisfactorily. Therefore I decided to do my own testing in a controlled environment, right in my own house, to settle the issue once and for all.

In our art-craft room, there is a wire strung across one wall where we can display the kids' artwork. So I took their stuff down, and hung page after page of newspaper instead. I had decided to use newspaper because it’s fairly large, and has lots of fine detail on each sheet. Then I set up some bright lights and my camera, and put the two lenses through their paces.
I took a total of 96 photos — one picture at each possible f-stop, with each lens set at three different focal lengths: short, medium and long. For the display purposes below, I've narrowed it down to 18 photos — for each of the three focal lengths, I've included a picture taken with the largest aperture, the smallest aperture, and an aperture in the middle.

All of the following section images where taken from the edge of each picture (at 100% magnification), since that is the part of the image I’m trying to test for sharpness. Also, note that the Sigma lens has a fixed aperture range over the entire focal length, while the Sony lens does not. Therefore, the apertures below for the Sony lens will vary, depending on the chosen focal length.

So let’s start with the shortest focal length (widest angle) and smallest aperture (largest f-stop).

Sigma lens at 10mm, f/22


Sony lens at 11mm, f/22
Neither image is very good, but I would say the Sony is somewhat better. Next, we have the shortest focal length with a middle aperture:

Sigma lens at 10mm, f/9


Sony lens at 11mm, f/10
In this case, the sharpness of the Sigma lens is noticeably better than the Sony. Next, we have the shortest focal length with the largest aperture:

Sigma lens at 10mm, f/3.5


Sony lens at 11mm, f/4.5
Once again, the sharpness of the Sigma lens is quite a bit better than the Sony. Now we’re going to switch to a medium focal length, and run through the three aperture settings again:

Sigma lens at 16mm, f/22


Sony lens at 15mm, f/25
In this example, I would say that the Sigma holds a slight edge. Next we’ll try a medium focal length with a middle aperture setting:

Sigma lens at 16mm, f/9


Sony lens at 15mm, f/11
In this case, the sharpness of the Sigma lens is much improved, and way better than the Sony. Next is a medium focal length with the largest aperture:

Sigma lens at 16mm, f/3.5


Sony lens at 15mm, f/5
Once again, the Sigma lens is the clear winner. Now we’ll move on to the longest focal length, starting again with the smallest aperture:

Sigma lens at 20mm, f/22


Sony lens at 18mm, f/29
In this example, the Sigma lens comes out on top again. Next, we’ll try the longest focal length with a middle aperture:

Sigma lens at 20mm, f/9


Sony lens at 18mm, f/13
In this case, the Sigma lens is significantly better than the Sony. Finally, for our last test, is the longest focal length with the largest aperture:

Sigma lens at 20mm, f/3.5


Sony lens at 18mm, f/5.6
Once again, the Sigma lens shows it superiority over the Sony lens. Wow! If you ask me, it’s a total rout! In only one of the nine tests was the Sony lens sharper, and that was by a small amount. In the other eight tests, the Sigma lens was clearly the sharper lens — sometimes by a large amount.

Well, my question has been answered. I’m going to keep the Sigma wide-angle zoom lens, and sell the Sony one. I've also learned that if I want the sharpest photos, I need to stick with a medium aperture, and definitely stay away from the small apertures.
Brian's Photo Blog — Article 99
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Reader Comments
On June 7, 2012, Gil wrote:
Thanks for posting your test. It was very informative. I'm still considering between the f3.5 vs the f4-5.6.
 
Brian's Photo Blog — Article 99
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