Third-party lenses are sometimes looked down upon by the sort of photographers who insist you can only take a good photo if your lens says Canon or Nikon on it. But, not only do some outperform their branded counterparts, others do something which mean they don't even have first-party rivals. The new Sigma 18-35mm F1.8 DC HSM Art, for example, is the world's only zoom lens to achieve a maximum aperture F1.8 throughout the entire range.
Most constant aperture zooms, even those targeted at pros, peak at F2.8 – with exceptions including the Olympus 14-35 mm F2. This is why many photographers also have faster prime lenses in their kit bag for when they need those extra light gathering properties or an ultra-shallow depth of field. With its constant F1.8 aperture, the Sigma 18-35 mm F1.8 DC HSM lens could mean you don't need to carry as many lenses with you.
Designed to be used by DSLRs with APS-C size sensors (it will not produce an image circle big enough to cover a Full-Frame sensor), the lens will be available in Canon, Nikon or Sigma mounts, and gives the the 35 mm-format focal length equivalent of 27-52.5 mm. This means it should be good for shooting subjects including landscapes, portraits, still-life, or general casual photography … and that F1.8 makes it a massive step up from a typical kit lens.
Part of Sigma's new Art range of lenses, which includes the very impressive 35 mm F1.4, the new 18-35 mm is constructed from 17 elements in 12 groups. Use of a wide glass-molded aspheric lens and Special Low Dispersion (SLD) glass are said to compensate for aberrations and curvature at the widest angle, while the lens’ Super Multi-Layer Coating is stated to reduce flare and ghosting and provide sharp and high contrast images. A nine-bladed diaphragm should also contribute to a pleasing Bokeh effect.
Quick and quiet autofocus is provided thanks to Hyper Sonic Motor (HSM) and the lens incorporates Sigma’s improved AF/MF switch for quickly changing between manual and autofocus modes. Internal focusing and zooming means the 28.6 oz (811 g) lens does not change its 3.1 inch diameter x 4.8 inch length (78 x 122 mm) size when being used.
Additionally, the front part of the lens does not rotate, meaning special 72 mm filters like circular polarizers can be used, and the Sigma 18-35 mm F1.8 DC HSM has a minimum focusing distance of 11 inches (28 cm) for close-up subjects. Compatibility with Sigma’s USB Dock means users will be able to update lens firmware and adjust focus parameters from their computers.
Sigma has not yet provided a release date or price for the Sigma 18-35mm F1.8 DC HSM Art.