I understand that circumstances can stymie focusing but what I was
concerned about were reviews that talk about a particular lens' inabilty
to focus well or that it hunts more than another lens. Currently I have
all manual focus lenses and I am trying to determine if an AF lens would
be better to photograph my son's soccer games and sort of veered off
into how AF works.
Larry Cook
So the answer is that the camera possess the algorithms for AF but
the performance is based both on the algorithms and how responsive
the lens mechanism is? If that is correct then a lens that seems
to "hunt" more than another is not directly at fault? It is the
camera algorithms not being able to adequately handle the
responsiveness of the lens? Interesting. Of course you would still
want to avoid such a lens because it is the system as a whole that
is important and therefore an unresponsive lens that causes the
camera to hunt is still a bad thing regardless of which component
is actually "at fault".
Unresponsiveness or hunting can be induced by a variety of external
factors that have nothing to do with the equipment, as well.
Trying to focus on a low contrast subject that gives the AF nothing to
latch onto will cause hunting. Low light levels will cause hunting,
and this problem will be exacerbated by a slower lens.
Some third party lenses won't work as well with some cameras as first
party lenses.
Consumer market equipment may not be a responsive as pro market equipment.
It isn't possible to get a camera/lens combination that will perform
100% flawlessly 100% of the time.
I think it is a good idea to focus manually whenever auto focus isn't
required. This way, you will have that skill in place for when you
need it.
William Robb
