In my first hands-on for the 17-70mm f2.8-4 Contemporary, I investigated all the major features except for the wide-angle. No opportunity presented itself to use the shorter focal lengths. In January, I had the time to shoot the missing wide-angle photos and to get an idea of the image quality the 17-70 C offers on the shorter end. As already mentioned in December, the wide-angle is basically the Achilles’ heel of as good as any standard zoom and the 17-70 C doesn’t seem to be any different, judging from the photos.
While the 17-70 Contemporary can indeed resolve as high as the highly sophisticated 15MP Foveon on the long end, especially if you stop down 1 to 2 stops, the resolution at the short end still remains clearly below the capabilities of the Sigma-sensor. It is not just the corners which are problematic, but also the area between the middle of the frame and the corners (approx. 60% of the image area). At open aperture, f/2.8 that is, you should refrain from taking landscape pictures, since the sharpness offside the middle doesn’t anywhere near suffice for such subjects. By stopping down, contrast and sharpness can be enhanced, but the biggest wide-angle performance problem of the 17-70C is the fact that it isn’t totally sharp even at f/8 and f/11. Now I haven’t done a comparative study, but the 17-70mm C doesn’t appear to be any better than Sigma’s 18-250mm HSM Macro superzoom in this discipline. Which is saying a lot. I cannot recommend the 17-70mm C to landscape photographers and others in need of good and consistent sharpness from corner to corner, unless the weak wide-angle range is covered with an ultra wide-angle lens, the way I do it (10-20mm f/3.5). Other than that, you can attain happiness with the 17-70 C, provided you’re ready to compromise or only use wide-angle from time to time. As already mentioned in my first hands-on report, the 17-70 C is well made, provides good image quality from wide-angle onwards and has a very short closest focusing distance, which comes in handy for casual macros. Still, if you’re looking for a standard zoom that is sharp through its the entire focus range you should rather opt for the 17-50mm f/2.8 EX or the new 18-35mm f/1.8 Art.