On Wed, 29 Jul 2015 15:17:19 -0400, PeterN
wrote:

On 7/28/2015 11:35 PM, nospam wrote:
In article , Bill W
wrote:

What is 3D tracking? My problem at this air show location with all
those focus points is that it will start focusing on the power lines,
trees, mountains, clouds, etc. Does it mean that it tries to track
objects that are at a consistent distance? My Pentax does not have
that option, so it might be moot anyway.

http://www.nikonusa.com/en/Learn-And...i4lx/3d-focus-
tracking.html
An invaluable feature for sports, action and wildlife photography, 3D
focus tracking, available in select Nikon D-SLRs, automatically
shifts the focus point to follow the movement of the subject. With
the shutter release pressed halfway, you'll see in the viewfinder the
lens continuously maintain focus as the subject moves.

However, maintaining focus doesn't guarantee a sharp image, as there
is a short time lag between the release of the shutter and the
capture of the picture. To solve this problem, the focus tracking
system is a predictive system that uses special algorithms to
forecast the position of the subject at the moment the image is
captured. The prediction is based on a measurement of the subject's
movement and speed.

Okay, not exactly what I was thinking. If I use too many focus points,
I too often end up focused on the wrong subject, but with too few, I
lose the subject too easily after I lock onto it. It's just a matter
of practice, I suppose.

it depends on the focusing mode and given situation. no one mode is
best in all cases, which is why there is more than one mode.

here's a description of the various mode:
https://photographylife.com/dslr-autofocus-modes-explained


Yep! and as BillW stated, it takes practice. I don't think reading the
manual in the field is very practical.

Yep, what happens with smallish objects is that I can't find them in
the viewfinder quickly enough, so then the camera starts to focus on
background or foreground objects, leaving the lens completely out of
focus for the subject I'm looking for, which then makes it harder yet
to find. It's mostly me, but also the fact that I'm not using the best
equipment for that sort of thing. Luckily, when something is just a
hobby, one doesn't need the best equipment for anything. I can live
with missed shots. It's not like I'm letting the Pulitzer get away.