david vt wrote:
These refer to focus group elements used by the camera. Single is exactly that - spot focus using the focus element (normally center, but can be moved). D9 refers (at least in Nikon speak - don’t know Canon) to the 9 center elements for a small group average. From there, it gets bigger (D15, D21, etc depending on the body).
I had pretty good luck in group last year with the 500.