@crockny wrote:
2. I use the center focus single spot except when close to a bird when I move the single spot around..
If you are actually in "spot" mode then this is likely a problem (and possibly "the" problem that causes your lens to stall).
On the 5D III you can set the focus to use a single focus point but not in "spot" mode. You can also use the point in "expanded" AF mode (the single point will borrow the points above, below, left, and right to assist in locking focus on that point) or you can use "surround" AF (it will use all 8 points adjacent to the selected point).
But if you use "spot" mode then it will use a single point ... and a REDUCED size. This is almost certainly not what you want for a bird-in-flight.
Suppose you are taking a close shot of a subject at an extremely low focal ratio (e.g. suppose I have Canon's 50mm f/1.2L lens and I'm using it at f/1.2 so my depth of field is extremely shallow). You probably want accurate focus on the subject's eye but will let the focus fall off artistically for the rest of the shot. In this situation you may want to make sure the camera focuses in on the structure in the iris of the subject's eye and absolutely nothing else... so you can set the camera to use the "spot" focus which will reduce the AF area -- pretty much guaranteeing that it will not try to focus on anything "near" the eye... just the actual eye. That's a good reason to use the "reduced" AF area of "spot" focus mode. Basically the "spot" mode is for situations where you have shallow depth of field and want to make sure it locks onto exactly the thing you want and nothing else. If you have a broader depth of field then there's probably little point in using "spot" AF.
But in order to focus the camera has to be able to lock onto enough contrasty structure. It probably can't do this for a bird-in-flight. By expanding the focus area you let the camera get a larger section in order to find some good contrasty structure that can help it lock focus.
I would try changing the focus mode either to expanded AF or surround AF. Expanded AF is the mode that has 5 points in a "+" shape (technically it's a single point but it's "borrowing" the points above, below, left and right to make it easier to identify contrast and lock focus). Surround AF is the mode that grabs the box of 9 focus points. It really wants to focus on the center point but it is "borrowing" all 8 of the surrounding points.
There's also zone AF or the full auto-select (all AF points are fair game in that mode).
It should have a much easier time locking focus if you give it a larger focus area.
Tim Campbell
5D III, 5D IV, 60Da
More time than nudging the lens.
