The Sigma 18-35mm F1.8 DC HSM lens features a maximum aperture of f/1.8 throughout the zoom range. This lens is ideal for portraiture and indoor photography. It's a good combination of a wide range of focal lengths in a compact design. The 9 blade rounded diaphragm creates an attractive round bokeh at large-aperture settings. Designed to minimize flare and ghosting Flare and ghosting were thoroughly measured and monitored from an early stage in the lenses development to establish an optical design which is resistant to strong incidental light such as backlight. The Super Multi-Layer Coating reduces flare and ghosting and provides sharp and high contrast images even in backlit conditions. Attaching the matched petal type hood, which is supplied, will provide extra protection from flare and ghosting. Minimum focusing distance of 28cm With a minimum focusing distance of 28cm and a maximum magnification ratio of 1:4.3, this lens is excellent for close-up photography. Hyper Sonic Motor The HSM (Hyper Sonic Motor) ensures a silent, high-speed AF function. Optimizing AF algorithm, smoother AF is achieved. It also enables full-time manual focusing capability which allows sensible focus adjustment by simply rotating the focus ring. Brass made bayonet mount This lens incorporates a brass made bayonet mount which has both high accuracy and durability. A special treatment to reinforce its strength is applied to the surface giving it greater strength and making it highly resistant to long-term