(it reaches focus, then GOES OUT OF FOCUS, then back again), so to have a picture in focus you should pray to the odds and it will probably be 1/3 of the times in focus, 1/3 back focus and 1/3 front focus if you are using a wide aperture and shallow DOF

You do lose a little shallow DOF (not enough of a difference for it to mean much to me)

Will this do all of the 3-D focus tracking like the D7100 will?

The entire Fujifilm line of cameras, as well as the Fujinon lenses (yes, the cameras are called "FujiFILM" even though most Fuji cameras do not use film, and the lenses are called "FujiNON;" the entire imaging division is a part of the larger company, Fuji Heavy Industries) seem simply to rack up one stellar review after another, and this ranges all the way from the entry level X-A1 camera (which knocks out some superlative photos in spite of being a cheap-o camera with a cheap-o kit lens) all the way to XPro1 and X-T1 models, which are much more expensive, and aimed at a different audience

These lenses are so good that even when I shoot with my cheap-o X-A1 entry level Fuji camera, the results can be extraordinary