A #1 top seller on B&H Photo, and for good reason.

The imagery is bright, cinematic, beautiful. I shoot everything on this.

From their own product description:

"As part of the Art line within Sigma's Global Vision series, this lens is designed to achieve truly notable optical performance and is ideally suited for creative and artistic applications.
Wide-to-normal zoom is designed for APS-C-format Canon EF-mount cameras and provides a 28.8-56mm equivalent focal length range.

Impressively bright constant f/1.8 maximum aperture is well-suited for working in low-light conditions and also provides greater control over the focus position when using shallow depth of field techniques.
Five Special Low Dispersion (SLD) elements are featured in the optical design and help to reduce color fringing and chromatic aberrations for improved clarity and color accuracy.
Four aspherical elements are used to help limit distortion and spherical aberrations and also contribute to greater overall sharpness and accurate rendering.

A Super Multi-Layer Coating has been applied to lens elements in order to minimize lens flare and ghosting and contribute to producing contrast-rich and color-neutral imagery, even in backlit conditions.

Integrated HSM (Hyper Sonic Motor), along with an internal focusing system, realizes quick and quiet autofocus, which is further complemented by an optimized AF algorithm to produce smoother focusing performance. The HSM also permits full-time manual focus control simply by rotating the focus ring at any time.

Rounded nine-blade diaphragm contributes to a smooth and pleasing bokeh quality.

Constructed using a Thermally Stable Composite (TSC) material for greater precision and use in wide temperature variations. Additionally, a brass bayonet affords improved mounting accuracy and rigidity.
This lens is compatible with the optional Sigma USB Dock for fine-tuning different lens characteristics and updating its firmware."