When the D5 got the horizontal line (and vertical) group area mode, I wanted to use it in such a way that I could move the subject's position in the frame and just hold it on the line and it would keep it focused, but the gaps in the sensor array made this less practical than I hoped. In the D6, the gaps are narrower and there are fewer of them, basically there are three groups of five columns of sensors, and the groups are virtually gapless, but it's possible for the subject to fall within one of the two gap columns between groups. I played with this when photographing deer hanging out in a field, and basically as long as one is aware that these two gaps exist, it is easy to use the custom group modes and it does as you'd expect, focusing on the closest subject.
In the D6, the single-point AF has the choice of wide and normal coverage, and I wondered if this setting could be used to cover the gap columns in group-area mode, but it can't. According to the manual, the single point watch area setting affects single point and dynamic area modes, but no mention is made of its effects on group-area AF. In my testing I was able to confirm the wider and narrower single-point areas have a real difference; basically in the wide watch area setting, one can assume the camera will focus on detail that is just outside of the single-point brackets reliably if there is nothing clear to focus on within the brackets themselves (which is the normal watch area). However, in dynamic-area the difficulty is that it's dynamic, so it's more difficult to demonstrate the difference. I believe it is there as indicated by the manual. In custom group area mode I wasn't able to see a difference due to the single-point watch area setting, which is consistent with the reference manual's description. Nikon suggest the wide setting should be used for fast-moving subjects.
What I like about the custom group area setting is that it allows me to accommodate a deer or bird who changes direction or orientation and maintain good composition without necessarily moving the focus area. I typically use horizontal lines when photographing deer on the move, it gives me some forgiveness for not being able to hold the subject's eye perfectly under the selected focus point but is less likely to focus on background or grass than dynamic-area modes. Group area focusing has closest-subject priority built in and this is true of custom group area as well as the standard one. I felt that custom group area with a horizontal line worked really well for photographing flocks of birds at distance, as it reliably allowed me to avoid focusing on grass and gave enough focus points (adjustable!) so that I could be sure that at least one point was on a bird, so I avoided both focusing on foreground grass as well as background trees behind the birds. But, when using this technique it is good to remember the two gaps even though they are narrow, they are still there.
For photographing a single subject at close distance, dynamic area is probably better as one can apply it with greater precision on the eye, but for distant animals, custom group area is my favorite mode now. When using dynamic area on distant animals, often the depth of field is such that the system can pick up on background objects instead of the main subject and this was a common problem when using dynamic area with Multi-CAM 20k bodies. Now there are more options to work with. I think the custom group-area is likely to become quite popular when the system is adopted into less expensive camera models. I will try to make some screen shots from Nikon ViewNX-i that show the custom groups in action so you can get an idea of how they can be used.
3D tracking now shows multiple focus points in use over the subject, this is seen in the viewfinder as well as in ViewNX-i if settings to display focus point are turned on. Previously the 3D tracking showed only one active focus point. I think the new system is clearer as it shows what the camera considers to be the subject (often in the previous cameras the selected point seemed to be outside of the subject even though focus was correct! This is probably because of the 153 focus points, only 51 were displayable so the camera and browser would show the closest match but it sometimes wasn't the actual focus point the camera had used if it used one of the in-between points that are invisible). The D6's way of showing what the camera focused on is much more clear and believable. 3D tracking seems to now able to overcome the situation where the selected subject that is being tracked is temporarily occluded by a subject going across the line of sight, and can maintain focus on the selected subject. In the previous models, if I was using 3D to focus and track a person, it would almost always lose the subject if another person walked across the subject. 3D now works much better in the D6. I did manage to get it confused when a skateboarder in black clothes went behind a black lamp pole and the camera did get confused and stuck to the lamp pole. However, in most cases it worked perfectlỵ.
There is now a setting if activated, your selected point guides auto-area AF to start from focusing on the selected point and then it continues doing its auto-thing. What's more you can have the camera switch from 3D or auto-area into single point and it retains the automatically tracked subject as the selected point in the mode where one can manually move the focus point around. This seems very fluid. I will test to see how easy this is to use in practice.
In the D850, I've found I get noticeably sharper results hand-held with my 500 PF when using EFCS with Qc rather than normal drive mode (S or CL/CH). The D6 has Qc with 1-5 fps (user selectable) and it supports EFCS. However, I haven't been able to see a clear improvement by using EFCS in these hand-held situations with the D6, it's possible that the camera's normal drive modes are sufficiently well-damped, or it could be the lower-resolution sensor. I will try to more to see if the difference from use of EFCS is visible at some shutter speeds and conditions.
Overall, I am very pleased with the new camera. The customizability of controls and level of refinement especially in the autofocus are great. I hope Nikon puts out updated D850 and D500 models with as much of these features imported as possible so that more people (and those who prefer high-resolution sensors) can take advantage of the development.
