Sigma 18-50mm f/2.8 EX DC Macro HSM
In 2007, Sigma upgraded the Nikon mount version of its very popular standard zoom and fitted it with a focus motor. However, optical construction is equal to the older version.
As often with Sigma, quality differs somwhat between samples. Most samples of this are soft at f/2.8, but this is usually a good lens from f/4 and up to f/16 (where diffraction sets in) across all focal lengths. But as the extra stop is the main incentive to upgrade from the "kit" lens to this - its mediocre performance at f/2.8 is a letdown.
Despite the EX designation, this is not a top grade lens. In contrasty situations CA, flare and ghosting are visible. Samples tend to vary a lot – even more than usual with Sigma. A good sample can be considered good value, a bad one is horrible. You may need to try out two or three before you find a good one, so don't buy this over the net.
This lens competes directly with the Tamron 17-50mm f/2.8 in zoom range and price. Compared to the Tamron, the Sigma is less sharp, has more CA, and suffers from flare and ghosting.
The focus motor is faster and quiter than Tamron's gear drive, but it is not as fast and quiet as the SWF in the Nikon 17-55 mm f/2.8. However, I think it is a real ring motor.
Rating: Ed: 45, User: - (normalized, 0=useless, 50=average, 100=excellent).
Mount: Nikon F.
Aperture range: f/2.8 to f/22.
Optical zoom: 2.8x.
Close focus distance (CFD): 20 cm / 0.66 ft (from sensor plane).
CFD magnification: 1:3 / 0.33X.
Focus: AF (built-in, ring-type).
Filter diameter: 72 mm.
L x D, W: 86 x 79 mm, 450 g.
Approximate street price: USD 419 (new, w/o tax).
Sigma is a family owned manufacturer of photographic equipment founded in 1961 in Japan. The company's main business is to manufacture third party lenses. However they also produce third party flash units and, since 2002, their own line of DSLR and compact cameras. Sigma's digital cameras use a special sensor, developed by Foveon, that records full color information for every pixel. In late 2008 Sigma acquired Foveon.