Nikon has tweaked the excellent D4 with the announcement of the D4S. While the cameras are nearly identical on the outside, the Nikon D4S includes a few important upgrades. Arguably the most notable of the upgrades is a 30 percent faster recording speed, thanks to an upgrade in the processor. Nikon has also added a new file format--RAW Size S, a RAW file that's about half the size for when memory card space is at a premium or faster record times are necessary. The D4S is slightly faster in burst shooting at 11 fps (to the D4's 10) and can record 200 JPEGs in a row. Video quality also saw a boost, going from 30 fps to 60 fps. The battery has also been upgraded, rated at over 400 shots more than the D4. There's no question the D4S is Nikon's top camera with excellent image quality. Whether or not D4 owners should upgrade isn't as easy to answer, but most probably won't see a huge difference for the expense.