Many people (including me) prefer using the sub-selector button to change AF areas. I think it's especially appealing to people crossing over from some higher-end Canon bodies that offer a similar control. This wouldn't be the only area where Nikon has deliberately targeted Canon users with custom features and controls that make Nikon bodies more similar to Canon ones.
Sat 31-Aug-13 10:34 PM | edited Sat 31-Aug-13 10:52 PM by walkerr
It remains useful for menu selections, browsing through images in playback mode, etc. In addition, there are two sub-selector buttons on the back of the camera, making it easier to change AF locations when you use the camera in a vertical orientation. At least for me, it's much more comfortable to use these buttons in either orientation than the one multi-control dial. The latter was a consistent complaint of photographers with the D3 series.
I typically use my right thumb (I'm generally right-handed when it comes to camera, though I can be ambidextrous at other activities. I think most SLRs favor the right-handed.) for two activies on my D4: Activating (or locking) AF, and changing the starting autofocus point with the sub-selector.
Here's a trick it took me a while to master: If you rest the ball of your thumb on the center of the sub-selector, you can spin the selection point around without ever taking yout thumb off the sub-selector. If you don't stab at a point, but activate it in a direction, you can move the target point in a line.
It helped me to not think of the sub-selector as a bunch of single-contact switches, but as a continual trackpad sort of thing. The only problem is getting your brain around WHERE the new point will be relative to where yout thumb is dragging and where the point was when you started.
I don't use the main selector when taking pictures, only when editing or chimping.
Thanks Arthur and Rick, I have been generally ignoring the top sub-selector, but will give it a try as a preferential tool for moving the AF points. For my style, moving the AF points is a constant action so is very important to me!
BTW, I find turning Wrap-On to be another key feature (A6). One can quickly get from left to right, top to bottom etc. using this feature. It takes some getting used to but again a very good feature.
I too was irritated by this wasted input device. It was a duplication of input with little differentiation. If they had only made it individually customizable. I think the did it so that the joysticks felt identical in horizontal and vertical camera orientations.