SIGMA AF 20mm F2 DG DN HSM |C - SONY E

The latest in Sigma’s growing range of ‘I-series’ prime lenses for Sony E and Leica L mount mirrorless cameras, this is a typically compact and lightweight lens, despite featuring a robust, full-metal construction and a high-quality optical path. It combines intuitive handling with fast autofocus and impressive image quality, making it an ideal ultra-wide-angle lens for architectural interiors, sweeping landscapes, astrophotography and more besides.

Sigma’s Contemporary lenses don’t go overly fast on aperture ratings, instead keeping the size and weight to easily manageable levels.

 This 20mm is no exception, giving a generous field of view on full-frame mirrorless cameras, equating to 95.5 degrees on the diagonal, yet the lens measures just 70x72mm in size and weighs a mere 370g.

There’s some impressive glass shoehorned into the diminutive construction, with 13 elements in total and featuring

 three high-precision glass-molded aspherical elements, one SLD (Special Low Dispersion) element and one top-spec FLD (‘Fluorite’ Low Dispersion) element.

 Sigma’s conventional Super Multi-Layer Coating and more high-tech Nano Porous Coating are both employed.

The overall aim is to produce high levels of sharpness across the entire image frame, as well as minimizing sagittal coma flare, important for maintaining the integrity of bright pinpoints of light in astrophotography.

Like other lenses in Sigma’s I-series Contemporary line-up, the 20mm has impressive build quality based on a coated brass mounting plate,

 a metal barrel and even a metal lens hood and lens cap, the latter of which is magnetic.

 A more regular plastic lens cap is also supplied in the box. The construction features multiple weather-seals and is dust- and moisture-resistant.

Handling is enhanced by an aperture control ring which operates in one-third f/stop increments as well as featuring an A (automatic exposure) position just beyond the narrowest setting of f/22.

However, there’s no ‘de-click’ option for stepless aperture control when shooting video, nor a locking switch for the auto exposure setting.