Sigma have come up trumps with their announcement of the world’s first F1.8 constant aperture zoom lens. The 18-35mm f/1.8 DC HSM Art lens is  a wide-aperture, standard zoom lens offering a useful 27-52.5mm focal range on DSLR cameras with APS-C size sensors. Weighing in at just 810 grams (that’s somewhere between a dozen Krispy Kreme [...]