The Sigma 50mm F1.4 DG HSM 'Art' is a fast normal prime for full frame cameras, with an unusually complex optical design. However at $950 / £850 it's substantially more expensive than either its predecessor, or Canon and Nikon's 50mm F1.4 lenses. We've already published lab test data showing that it's optically excellent, but what does this mean in real-world use? Read our detailed review to find out.