Autofocus is a little sluggish and more noisy than in any other lens on test. As in the Sigma lenses and the Tamron 18-270mm, the focus ring rotates during autofocus, so you have to be careful to keep your fingers out of the way. The zoom ring feels slightly stiff, too, but there’s no hint of zoom creep. Overall image quality is pretty good for a superzoom, though without stabilisation you’ll need steady hands, especially at the long end of the zoom range. Compared with the first incarnation of the Sigma 18-200mm OS (OS stands for Optically Stabilised), the second edition was 12mm shorter and weighed 120g less. This third edition is 2mm shorter again and a further 60g lighter, making it the second lightest in our test. It weighs 430g, compared with the Tamron 18-200mm’s 405g. What definitely isn’t short is its name, but what do all those letters and numbers actually mean?
As with many superzooms, the widest aperture shrinks from f/3.5 to f/6.3 as you go through the zoom range and, as a ‘DC’ lens, it’s designed for cameras with DX-format