The Sigma 18-35mm f1.8 DC HSM Lens is the first wide-angle to zoom lens (as of 22nd April 2013) to achieve a maximum aperture of f1.8 throughout the entire zoom range. The 9 blade rounded diaphragm creates an attractive round bokeh at large-aperture settings, while the HSM (Hyper Sonic Motor) ensures a silent, high-speed AF.
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