Sigma 17-50mm F2.8 EX DC OS HSM

The Sigma 17-50mm F2.8 EX DC OS HSM is a good candidate for replacing a DSLR's kit lens.

The kit lenses supplied with many DSLRs are perfectly adequate if you're just starting out, but their low cost typically comes at the expense of optical quality. If you're thinking about upgrading your kit zoom, Sigma’s 17-50mm F2.8 EX DC OS HSM FLD is definitely worth looking at, given its constant F2.8 aperture, Optical Stabilization system and its availability for five systems.

The 17-50mm features two of Sigma's 'F' Low Dispersion (FLD) elements, as well as two further glass mold aspherical elements and a hybrid aspherical element. Its Hyper Sonic Motor is claimed to be fast, quiet and more precise when focusing than conventional varieties, and thanks to an internal focusing system the lens maintains a constant size while focusing.

Not unexpectedly, given the popularity of the focal range, this lens isn't the only third-party standard zoom available on the market. Its closest competitors are the Tamron SP AF 17-50mm F2.8 XR Di II LD Aspherical (IF) and its similar but optically stabilized SP AF 17-50mm F2.8 XR Di II VC LD Aspherical (IF) variant, both of which are cheaper than Sigma’s option, but are not available for as wide a range of lens mounts.

Key Features/Specifications

  • Four Super-Low Dispersion (SLD) and three aspherical elements
  • Optical Stabilizer system
  • Available in Canon EF, Pentax KAF3, Sony Alpha, Sigma SA, Nikon F (DX) mounts
  • Maximum format size: APS-C / DX
  • Dimensions: 84 x 92 mm (3.62 x 3.29 in)
  • Weight: 565 g (1.25 lb.)

Pros - Constant F2.8 aperture, Optical Stabilizer
Cons - Cheaper Tamron options available

Tamron 18-270mm F3.5-6.3 Di II VC PZD

The 15x optical zoom of the Tamron 18-270mm F3.5-6.3 Di II VC PZD features Tamron's optical Vibration Compensation (image stabilization) system.

So called ‘superzoom’ lenses are popular for obvious reasons - they combine a versatile zoom range with the convenience of a single lens. The past few years have seen the zoom ranges of all-purpose superzoom lenses become increasingly broader, and the Tamron 18-270mm F3.5-6.3 Di II VC PZD - designed for cropped-format DSLRs - represents the most confident step taken yet by any lens manufacturer. It offers a huge zoom range that's equivalent to 27-405mm on Nikon DX and Sony APS-C bodies and 29-432mm on Canon’s APS-C models (in 35mm terms).

Focal length range aside, the lens is equipped with a range of performance-improving technology, including Tamron’s proprietary Vibration Compensation (optical stabilization) system which promises a compensatory effect of up to four extra stops of shutter speed (although only on Canon EF and Nikon F-mount models; as usual Sony owners get the benefit of in-body stabilisation). Tamron has also incorporated a Piezo Drive (PZD) motor for silent and rapid focus, while aspherical and low-dispersive elements are employed to maintain a high standard of image quality throughout the lens’s entire 15x zoom range - no mean feat.

A more affordable alternative to the Tamron lens is Sigma's 18-250mm F3.5-6.3 DC OS HSM. Despite culminating at a slightly shorter 250mm, the lens is similarly specified. Sigma’s Hyper Sonic Motor carries the same claims with regards to focus speed, noise and responsiveness as Tamron’s PZD system, while its Optical Stabilizer likewise promises a four-stop benefit in terms of usable shutter speed.

Key Features/Specifications

• 15x focal length range (27-405mm / 29-432mm equivalent depending on format)
• Four-stop Vibration Compensation system (Canon and Nikon mounts only)
• Available in Canon EF, Nikon F (DX), Sony Alpha (non-VC version)
• Maximum format size: APS-C / DX
• Dimensions: 74 x 88 mm (3.46 x 2.93 in)
• Weight: 450 g (0.99 lb.)

Pros – Class leading focal range, Vibration Compensation system
Cons – Sigma alternative is cheaper, some distortion and chromatic aberration visible at 18mm (common for lenses of this type)


Click here to read page 3 of our roundup of third-party lenses