Product information

17-50mm

Indicates range of focal length. The larger the number, the greater the magnification of distant objects. The smaller the number, the wider the angle of view.

F2.8

Indicates maximum aperture. The smaller the number, the “faster” the lens, meaning more light can enter to allow shooting under dim illumination. If only a single figure is given, the lens is a prime (fixed focal length) lens or a zoom lens that maintains the same F-number regardless of zoom position. If the maximum aperture of a zoom lens changes depending on zoom position, it is expressed thus: F4.5~5.6

EX

Indicates Sigma’s professional-grade prime and zoom lenses. Generally, these lenses retain the same maximum aperture regardless of zoom position. * Except for certain lens

DC

Indicates high-performance lenses designed especially for cameras with APS-C size image sensors. Vignetting will result if used on larger sensors. Lenses suitable for cameras with full-frame sensors are indicated by the DG mark, and lenses exclusively for mirrorless interchangeable lens cameras are indicated by the DN mark.

OS

Indicates lenses incorporating an Optical Stabilizer (OS) to compensate for camera shake.

HSM

Indicates lenses equipped with a hypersonic motor.

Function

EX

EX Lens

Sigma’s professional-grade prime lenses and wide-aperture zoom lenses that maintain their maximum F-number regardless of zoom position. * Except for certain lens

ASP

Aspherical Lens

Aspherical lenses offer greater design latitude, raise performance, permit use of fewer lens elements, and allow a more compact size.

APO

APO Lens

These lenses include one or more elements made of ELD (Extraordinary Low Dispersion), FLD (“F” Low Dispersion), or SLD (Special Low Dispersion) glass, which help minimize chromatic aberration, which can harm image quality. In wide-angle lenses, they help correct mainly axial chromatic aberration, while in telephoto lenses, they help correct mainly transverse chromatic aberration.

OS

OS Optical Stabilizer

An Optical Stabilizer mechanism built into the lens helps assure a sharp image while giving you freedom of movement and more latitude in camera settings.

HSM

Hyper-Sonic Motor

Using a motor driven by ultrasonic waves, these lenses offer speedy autofocusing and quiet operation.

RF

Rear Focus

Rear focus is one type of Sigma inner focus system, in which focusing is performed by moving particular elements within the lens interior.

IF

Inner Focus

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

CONV

Teleconverter-Compatible lens

This indicates a lens that will accept available Sigma APO TELE CONVERTER attachments, which increase focal length and support AE (automatic exposure) operation. Note: OS and HSM are not included on mounts for certain camera systems. Please see the specification charts on the following pages for details.