100-400mm lenses are some of the most versatile out there, offering a ton of reach suitable for everything from birds to landscapes, making them desirable for many photographer's kits. Nonetheless, such lenses can be pricey, which is what makes the Sigma 100-400mm f/5-6.3 DG DN OS Contemporary an intriguing option. The excellent video review takes a look at the sort of performance and image quality you can expect from the lens in the real world.