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Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
26.0mm
Aperture:
f/8.0
Exposure
1/800s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
50.0mm
Aperture:
f/2.8
Exposure
1/1600s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/7.1
Exposure
1/800s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/7.1
Exposure
1/500s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/7.1
Exposure
1/400s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/7.1
Exposure
1/500s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/2.8
Exposure
1/1600s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/7.1
Exposure
1/500s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
17.0mm
Aperture:
f/2.8
Exposure
1/1600s
Make
Canon
Model
Canon EOS 50D
ISO Speed
200
Focal Length
40.0mm
Aperture:
f/4.0
Exposure
1/800s
Verdict
The Sigma AF 17-50mm f/2.8 EX DC HSM OS is a highly competitive APS-C standard zoom lens and Sigma's best product in this class so far. It's not a flawless lens but none really is. Its biggest weakness is the performance at f/2.8 - the resolution in the image center is already exceedingly high here but the image corners are soft between 17-35mm and there's some vignetting at the extreme ends of the zoom range. However, starting at f/4 it beats or at least matches alternative products including the more expensive Canon EF-S 17-55m f/2.8 USM IS. The lens is extremely sharp across the frame here with no obvious flaw across the zoom range. The field curvature is also minimal (quite flat focus plane). Lateral CAs are not really field relevant. The distortion characteristic is about average for a lens in this class. The quality of the bokeh (out-of-focus blur) is slightly better compared to most competitors although you will naturally find prime lenses which perform better here.
The build quality is very good in absolute terms but the rotating focus ring in AF mode and, consequently, the lack of FTM (full-time manual focusing) are a bit disappointing especially because Sigma avoided theses issues in some of their other zoom lenses like the AF 8-16mm f/4.5-5.6 DC HSM. The AF is both very fast and near silent. The tested sample had also no problem with focus accuracy. Sigma's OS ("Optical Stabilizer") is, of course, a welcome new feature with an efficiency which is easily as good as its Canon counterpart.
