Sigma's compact constant f/2.8 standard zoom for APS-C mirrorless, a kit-lens killer.
The Sigma 18-50mm f/2.8 DC DN Contemporary was released as a compact constant f/2.8 standard zoom for APS-C mirrorless mounts, providing a 27-75mm full-frame equivalent range. At 290g and 55mm filter thread it is substantially lighter and more compact than full-frame 24-70mm f/2.8 alternatives. The DC designation confirms APS-C-only image circle; the DN designation confirms mirrorless-native design. Available in Sony E, Fujifilm X, and Leica L mount versions. Minimum focus distance of 0.121m at the wide end enables close-approach macro-adjacent wide-angle compositions.
The optical design uses 13 elements in 10 groups, including SLD and aspherical elements. Seven rounded aperture blades produce smooth bokeh. The 55mm filter thread is standard. At 290g the lens is the lightest constant f/2.8 standard zoom available for any APS-C system. Minimum focus distance of 0.121m at 18mm provides close-focus capability uncommon for a standard zoom. Stepping motor provides quiet continuous AF for video. Constant f/2.8 aperture throughout the 18-50mm range.
The constant f/2.8 in a 290g lens is the 18-50mm DC DN's defining practical proposition: for APS-C system photographers who want f/2.8 across the standard zoom range without full-frame weight and cost, this is the most compact option available. The 0.121m close-focus capability enables wide-angle close compositions — placing subjects very near the lens for dramatic perspective — that standard zooms with 0.25-0.35m MFDs cannot achieve. The 27-75mm equivalent covers wide-angle through short portrait on APS-C.
On the used market the Sigma 18-50mm f/2.8 DC DN is available at affordable prices for a constant-aperture APS-C zoom. Condition checks: stepping motor AF response for smooth video tracking, front element condition, and confirm the mount version matches the target body. Compatible with APS-C mirrorless bodies in the specified mount; the APS-C image circle causes vignetting if attached to full-frame bodies.