I've been shooting on full auto focus with all 51 points active and am somewhat puzzled at how it works. The focus point indicator moves around in the viewfinder and seems to be looking for the right point, especially in low light. In bright light I don't see it at all. I compose my pictures, as usual, and the subject seems to be in focus most of the time. How does it know what I'm shooting, especially in a busy composition?
Hi Doug,
As far as I know, there are certain algorithms which are applied in the camera in order to choose the most likely point of focus in a given composition. But this will not work in all situations.
If you are shooting P-mode, the camera might play with your aperture value to create enough depth of field in order to satisfy multiple focal points in the composition.
So the short answer is that if you want to be in control for 100%, you cannot depend on the camera making the choice for you. For most practical purposes, however, there is no harm in using the camera intelligence. As you apparently have discovered it for yourself
.
FWIW, I assign the focal point myself and focus and sometimes recompose. Although I try to avoid recomposing by choosing the most nearby focal point.
Cheers.