The 20mm F2 DG | Contemporary achieves the highest level of optical performance even at the widest aperture setting of F2 from the center of the image to the periphery. Based on the latest optical design technology, the lens construction includes three high-precision glass-molded aspherical lens elements, one SLD element, and one FLD element to suppress a range of optical aberrations. The result is clear and sharp images even in the extreme corners of the frame. By focusing on the suppression of sagittal coma flare, which is difficult to correct in post-processing, accurate reproduction of very bright points of light has been achieved. This also provides extremely detailed results across the entire image, which is especially important for night sky photography.

The surface of molds for glass molding, which is a process that forms optical components by pressing glass materials at high temperatures, requires ultra-high precision. Sigma uses high-precision molds whose surfaces are controlled with an accuracy of ±5 nanometers (0.000005 mm) or smaller. High precision aspherical glass molded lenses archives both good aberration correction and compact lens size.

The super multi-layer coating is combined with Sigma's unique coating technology "NPC (Nano Porous Coating)". The lens has been designed to be less susceptible to strong incident light such as backlight.

"NPC (Nano Porous Coating)" incorporates porous silica as the coating material. The porous silica layer has nano-sized holes with air inside. Having holes of this size enables a large reduction in the refractive index, allowing the reflectance to be lowered more than conventional anti-reflective coatings. As a result, reflected light causing flares and ghosting is sharply reduced, achieving clear image quality.

All I series lenses have an all-metal construction. The precision-cut aluminum parts not only give the barrel a sleek, stylish finish, but provide superb durability that improves the quality of the entire product. Metal materials are also used in internal structures that slide with the operation ring for added robustness. These high-precision components crafted with Sigma's cutting-edge metalworking technology are also used in Sigma's Cine Lens line-up for professional cinematographers and provide a tactile, ergonomic feel that make the lens a pleasure to use.

The cover ring between the focus ring and the aperture ring has hairline processing that is also used for the rear cylinder of the Art line. This covering functions as a finger hold when attaching or detaching the lens.

I series lenses are accompanied by a dedicated magnetic metal lens cap, in addition to a normal plastic cap. This dedicated metal cap clips to the front surface of the lens magnetically. It is no exaggeration to say that this meticulously crafted cap represents the finishing touch for the I series.

Inner focus system

To increase stability, this lens configuration uses movable internal lens elements that adjust focus without changing the length of the lens barrel.

Compatible with Lens Aberration Correction

Matching the optical characteristics of the lens, this function performs in-camera corrections of peripheral illumination, chromatic aberrations, distortion, and more, to further enhance image quality.

*Function available on supported cameras only. Available corrections or auto correction functionality may vary depending on the camera model.
*On cameras where lens aberration correction is controlled with 'ON' or 'OFF' in the camera menu, please set all aberration correction functions to 'ON' (AUTO).

Super Multi-Layer Coating

Sigma's own Super Multi-Layer Coating suppresses flare and ghosting by preventing reflections with in the lens. All lenses in the current Sigma range feature this original technology. In digital cameras, flare and ghosting may also be caused by reflections between the image sensor and lens surfaces. Here too, Sigma's Super Multi-Layer Coating is highly effective, assuring images of outstanding contrast.

Nano Porous Coating

NPC (Nano Porous Coating) incorporates porous silica as the coating material. The porous silica layer has nano-sized holes with air inside. Having holes of this size enables a large reduction in the refractive index, allowing the reflectance to be lowered more than conventional anti-reflective coatings. As a result, reflected light causing flares and ghosting is sharply reduced, achieving clear image quality.

Aperture ring

Aperture ring, designed to help users work intuitively.

Focus Mode Switch

Using this switch, it is possible to switch the focus mode between AF and MF.

A focus movement method of interchangeable lenses for mirrorless cameras in relation to the rotational angle of the focus ring during manual focusing. With "non-linear focus" the amount of focal point movement varies depending on the focus ring rotational speed. With linear focus, if the focus ring rotational angle is the same, the amount of focal point movement remains the same regardless of the focus ring rotational speed.

Stepping Motor

The lens is capable of smooth, quiet and high-speed AF made possible by a stepping motor, as well as supports Face/Eye Detection AF and video AF.

Mount with Dust and Splash Resistant Structure

The lens mount incorporates rubber sealing to protect the mount from dust and water drops.

Others

• Rounded diaphragm
• Compatible with high-speed autofocus
• Compatible with AF Assist (Sony E-mount only)
• Compatible with SIGMA USB DOCK UD-11 (sold separately / L-Mount only)
• High-precision, durable brass bayonet mount
• Support DMF and AF+MF
• Designed to minimize flare and ghosting
• Every single lens undergoes SIGMA's proprietary MTF measuring system
• Magnetic metal lens cap
• "Made in Aizu, Japan" craftsmanship

Lens Construction  13 elements in 11 groups

Accessory Camera Wall  No

Edition Number  C022

Sensor Size  Full Frame

Angle Of View  94.5°

Number of Diaphagm blades  9 (rounded diaphragm)

Minimum Aperture  F22

Minimum Focusing Distance  22 cm / 8.7 in.

Maximum Magnification Ratio  1:6.7

Filter Size  62mm

Dimensions  Sony E-Mount: 70mm x 74.4mm / 2.8 in. x 2.9 in.

Weight  Sony E-Mount: 370g / 13.1 oz.