Nikon's 2013 update to the full frame D600 adds a few minor changes to an already excellent full frame option. The D610 has the same processor and sensor as the D600, but the newer model has a redesigned shutter system that allows for shooting at 6 fps (compared to the D600's 5 fps), as well as a quiet shutter release mode that fires at up to 3 fps. The automatic white balance feature has also been redeveloped for improved color accuraccy and brillance. Nikon only has one camera that trumps this one, the D800, but the D610 is much more affordable and actually quite compact for a full frame. The D610 is similar in size to the D7100; in fact it's actually five ounces less. Users of the D600 don't have much reason to upgrade, but the D610 is an excellent full frame option.