Despite its relatively small size, the 400mm lens for Canon still comes with the big price tag you'd expect from a pro-grade supertele. At $6,900, it likely won't be showing up on the sidelines of many Pee Wee football games, but for travel-hardened sports, adventure, or nature photographers, diffractive optics could be a real boon. (Canon isn't the only one doing this: Nikon's latest 300mm lens, announced earlier this year, uses a similar technology called Phase Fresnel.) Whatever their moniker, smaller, sharper lenses will appeal to anyone trying to cram long lenses into overhead compartments or shoot with them for hours in the field. Ultimately, Canon's EF 400mm f/4 DO IS II is an upgrade in just about every possible way.