Review Sigma 17-70 mm contemporary
The Sigma 17-70 mm C is the first Sigma lens to be released in the Contemporary series ("High performance, yet compact and lightweight, true all-round lenses"). Since the first lens sets the tone, our expectations are high. Especially since the first lens in the Sigma Art line, the Sigma 35 mm 1.4 A, proved to be an outstanding lens in every review.
Sigma 17-70/2.8-4 DC Macro (OS) HSM "C" review
With a (just over) 4 times zoom range, you will get very different images without having to change your position. The field of view of this lens is equal to the field of view of a 26-105 mm lens attached to a camera with a full frame sensor, which makes it an ideal travel lens. A lens with a focal length of 17-70 mm is more universal than a lens which goes up to a focal length of 50 mm. For portrait photography, 70 mm is a perfect focal length for a camera with an APS-C sensor.
|Informative website: The new Sigma global vison website offers a lot of information about the design of the Sigma 17-70 mm contemporary, including MTF values and graphs showing the amount of vignetting and distortion. Usually the data producers provide on their websites, are based on the calculations used for the lens design. Above you can see graphs illustrating distortion.
USB Dock: For Contemporary, Art and Sports SIGMA lenses there's a USB dock with special developed software that allows you to connect to a PC. Then you can update the firmware, adjust the focus position and other parameters to suit your own preference. At the time of testing, the Sigma USB dock was not yet available.
Construction and autofocus
|The lens consists of a combination of metal and high quality plastic with a beautiful matte look. The lens mount is made of metal. Left of the lens mount you see a silver circle containing a "C", Contemporary, making this lens easily distinguishable from its predecessor. The lens has switches for AF / MF and image stabilization.
The zoom ring is nicely damped and runs very smoothly. If you zoom to 70 mm, the lens is almost twice as long. The front lens element does not rotate when focusing. Attached to a Canon 650D, autofocus is quick and quiet. Not completely silent, but much quieter than its predecessor.
|Due to the high resolving power of digital cameras, camera shake can be identified easily on-screen at a 100% magnification. If you're out shooting with a hand-held camera with an APS-C sensor, most photographers need a shutter speed at a 70 mm focal length of at least 1/250 second for a sharp image. Thanks to image stabilization, you can use slower shutter speeds.
For camera brands where image stabilization is not built into the camera (Canon / Nikon / Sigma), the Sigma 17-70mm Contemporary lens has built-in Optical Stabilization. The image stabilization does its job well: For images made without the use of a tripod at a focal length of 65 mm, the sharpness of the images drastically reduces at shutter speeds of 1/50 second or longer. But an image shot with a shutter speed of 1/6 second with the image stabilization switched on, is as sharp as an image shot without image stabilization at a 1/50 second shutter speed. That is a profit of at least 3 stops.
|Strictly speaking, the Sigma 17-70 mm "C" is no macro lens, because the imaging ratio of 1:1 is not realized. Still, you can shoot nice close-ups with this lens, since the shortest distance at which you can focus, is only 22 cm. You will be so close to your subject, the chances are great that you will throw a shadow on the subject.
At a focal length of 17 mm, the extreme corners are slightly less sharp than the center. It doesn't make much difference when you stop down. The longer the focal length, the smaller the difference in sharpness between the center and the corners. All in all a good performance.
|With a focal length of 17 mm, the vignetting at full aperture is clearly visible. At f/4 it will depend on your subject whether you will still recognize some vignetting: in photos with a clear blue sky taken with aperture 4 you could recognize it. But in practice, you will usually do not have to worry about vignetting with this lens. Vignetting is easily corrected with software correction, if need arise.
The measured distortion of the Sigma 17-70mm OS 'C' shows the character of a typical standard zoom lens with a relatively large zoom range. The distortion ranges from clear barrel at focal lengths under 24 mm just into pincushion at focal lengths above 50 mm.
Sigma delivers beautiful correction profiles to Adobe, which enable you to correct distortion in Lightroom or Photoshop. At the time of this review such a profile was not yet available, but it probably will be after the first update of Lightroom or the ACR converter.
|All-round zoom lenses for cameras with an APS-C sensor usually don't excel with bokeh. With the aperture wide open, this lens produces a relatively quiet background blur / OOF (Out of focus) rendering. A bright light source in the background becomes a beautiful circle, but in the bokeh rings are clearly recognizable. All in all, a marked improvement if you have a kit lens on a camera with an APS-C sensor (or an even smaller sensor), but the bokeh remains less beautiful than the bokeh of a fast lens on a camera with a full frame sensor.
|The previous version of the Sigma 17-70 mm OS was prone to flare. At this point, the Sigma 17-70 mm Contemporary really improved significantly. Even in the studio, we managed to induce a limited amount of flare only with a bright light shining directly into the lens. No images with ghosts were encountered during the test. Top performance.
In order to prevent shifting of colors ("chromatic aberration") as much as possible, Sigma used multiple types of high-quality glass (a-spherical, FLD and SLD). Chromatic aberration is so low at all focal lengths, that in practice you don't have to bother about it. Relatively speaking, the chromatic aberration is - not surprisingly - highest at a focal length of 17mm, but even then you will only see it when you blow up the image up to 300%.
Conclusion Sigma 17-70 mm Contemporary review