Sigma AF 18-50mm f/3.5-5.6 DC - Review / Test Report
Lens Reviews - Canon EOS (APS-C)

Review by Klaus Schroiff, published December 2005

Lens kindly provided for testing purposes by Werner van Loo


The Sigma AF 18-50mm f/3.5-5.6 DC is one of those lenses typically sold as a kit zoom often combined with the Sigma AF 55-200mm f/4-5.6 DC and a consumer DSLR. Nonetheless it is also possible to buy this lens independently for just a few bucks. As a DC (Digital Camera) lens it has a reduced image circle only compatible to APS-C DSLRs. Its field of view is equivalent to 29-80mm (36-100mm for four-thirds) on full format cameras.

The optical design of the lens is made of just 8 elements in 8 groups with one aspherical element. The AF 18-50mm f/3.5-5.6 DC is ultra compact at only 68x62mm and it weights just 250g. It has a min. focus distances of 0.25m which translates to a max. object magnification of 1:3.5 at 50mm. The filter diameter is 58mm. The aperture mechanism has 7 aperture blades. The package also includes a barrel-shaped lens hood. The lens is available for all APS-C DSLR systems plus four-thirds.

Regarding its price tag you shouldn't tank-like quality but it's actually quite decent by consumer standards without any overly shaky parts. The focus and zoom control rings operate pretty smooth. It's certainly better here than e.g. the low end-offerings from Canon such as the EF-S 18-55mm f/3.5-5.6. Typical for most zoom lenses the Sigma extends when zooming towards the long end (see above). The front element of the lens rotates when focusing so using a polarizer can be cumbersome. In AF mode the focus ring is coupled to the AF motor so it rotates during focusing which is a little sub-standard. The AF speed is pretty fast actually which surely originates in the light weight optical system.

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