24-70mm F2.8 DG OS HSM

Three SLD glass lens elements and four aspherical lens elements help minimize optical aberrations. To ensure outstanding image quality from the center to the edges of the photograph, the optical system minimizes coma, which causes points of light to streak, and transverse chromatic aberration, which cannot be corrected by adjusting the aperture. The optical system also minimizes distortion, which can be particularly evident in wide-angle shots, resulting in excellent optical performance throughout the zoom range.

Aspherical lenses necessitate refined expertise in the design and manufacturing of advanced, high-performance lenses. SIGMA’s representative products to feature this technology were the SIGMA 12-24mm F4 DG HSM | Art and SIGMA 14mm F1.8 DG HSM | Art, which both incorporated large ⌀80mm aspherical lenses as their front lens element.

Building on the success of these predecessors, the SIGMA 24-70mm F2.8 DG OS HSM | Art incorporates an aspherical lens element that helps achieve extremely high resolution. This element is much thicker at the center than the edges, and forming its unusual shape is a feat of manufacturing technology. Moreover, SIGMA processes the surface of this aspherical lens element with ultra-precise tolerances that are measured in hundredths of a micrometer. This extremely fine surface allows the SIGMA 24-70mm F2.8 DG OS HSM | Art to deliver a very natural and smooth bokeh effect, without the visible concentric rings that afflict typical aspherical lens elements.

SIGMA has continuously pioneered 24-70mm F2.8 lenses that are a step ahead of the times. The first model of this specification, SIGMA 24-70mm F2.8 EX DG ASPHERICAL DF, launched in 2001. Representing the fourth generation of the family, the new SIGMA 24-70mm F2.8 DG OS HSM | Art accomplishes a challenging feat in optical design: incorporating optical stabilizer functionality in a large-diameter standard zoom. By leveraging all of its design and manufacturing expertise, SIGMA has ensured that this new lens fulfills the uncompromising requirements of the Art line for image and build quality.

At wide-open aperture, this lens offers outstanding photographic expression. The area in focus is extremely sharp, while the background exhibits a beautiful bokeh effect with only slight spherical aberration. Since large-diameter zoom lenses are often used at wide-open aperture, SIGMA has paid close attention to the shape of the bokeh, aiming for perfect circularity.

The degree to which light is refracted by glass depends on the light’s wavelength. This fact causes different colors of light to focus at slightly different points. The result is chromatic aberration, the color fringing that is particularly noticeable in telephoto lenses. Most chromatic aberration can be removed by combining a high-refractivity convex lens element with a low-refractivity concave element. Yet residual chromatic aberration known as “secondary spectrum” may still remain. To minimize this secondary spectrum, which can be a serious issue with conventional lenses, SIGMA lenses feature up to three types of exclusive low-dispersion glass offering superior performance: ELD (Extraordinary Low Dispersion), SLD (Special Low Dispersion) and FLD (“F” Low Dispersion). In particular, FLD glass offers ultra-low dispersion in combination with high transmittance and the anomalous dispersion characteristics of fluorite. Meticulous deployment of these types of exclusive low-dispersion glass and optimization of power distribution gives SIGMA lenses superlative image rendition undiminished by residual chromatic aberration.

From the start of the design process, SIGMA measured flare and ghosting to establish an optical design that is resistant to strong incidental light sources such as backlight. At the prototyping stage, SIGMA used not only simulations but actual photographic experiments to assess flare and ghosting under multiple criteria, identify the causes of these issues under a wide range of situations, and take measures to mitigate them. In addition, SIGMA’s Super Multi-Layer Coating helps further reduce flare and ghosting and provide sharp, high-contrast images even in backlit conditions.

Designed for use in a wide variety of situations, the optical stabilizer (OS) offers a powerful stabilization effect of 4 stops*.

Since large-diameter standard zoom lenses tend to serve as a go-to lens and see frequent use, the SIGMA 24-70mm F2.8 DG OS HSM | Art is designed to stand up to the challenging shooting environments that pros encounter. To this end, the lens barrel contains a large amount of metal, while the external moving parts feature thermally stable composite (TSC), which is resistant to thermal expansion and contraction. This structure contributes not only to the outstanding optical performance of the lens but also to its high rigidity and confidence-inspiring build quality.

The newly designed hypersonic motor (HSM) offers 1.3 times the torque of its predecessor. Even at low speeds, it offers exceptionally stable performance.

The Nikon mount version of this lens includes an electromagnetic diaphragm mechanism that allows it to receive the appropriate signals from the camera body. This feature ensures precision diaphragm control and stable Auto Exposure (AE) performance during continuous shooting.

Full-time manual focus function allows the lens to be switched to manual focus simply by rotating the focus ring.

Since the area of the lens most vulnerable to dust and other foreign bodies is the mount, rubber sealing* helps provide peace of mind. In addition, the front lens element features a water- and oil-repellant coating that helps the lens perform well in the rain, near water, and in other challenging conditions.

The 9-blade rounded diaphragm creates an attractive blur in the out-of-focus areas of the image.

The brass mount combines high precision with rugged construction. Its treated surfaces and enhanced strength contribute to the exceptional durability of the lens.