Mornnb wrote in post #16919339
Birders use it because of it's AI Servo performance. A large number of AI points is a different thing to accuracy.
The 7D is great at AI Servo, but I have indeed noticed that the 6D can be more reliable in single point one shot mode.
Basically, what this is telling us is that the 6D's centre cross type is better than any of the 7D's AF points.
Lens Rental also says one reason for this is because recent bodies use a closed loop system making use of a AF position confirm sensor in the latest L lenses.
Each lens/body combination provides a different experience, and a certain lens/6D could work better than that same lens/7D, but the opposite could be true with a different lens.
Even Lensrental acknowledges this.
I’m not sure. It certainly seems that there are some camera-lens combinations that have more accurate phase-detection AF than others—when using center-point AF on a test target. It may actually be a big deal.
Regarding motorsports on a paved track, I am not sure that it is the most pressing use of an AF system. The cars follow a pattern, they are large subjects, nothing often gets in your way, they move in a 2D space, and you pan with them allowing a much greater success rate. Other sports that involves subject material moving erratically with other objects constantly interfering with your intended subject while moving in 3D space makes for motion that is much harder to configure for and track.
What that means is that 5 major factors goes into how well one body "works" for you vs another:
- Types of motion/activity/subject material
- The photographer's skill at that type of event
There are so many combinations that it is no wonder we get into these same "which AF system or body is best, and I have a budget to meet", there isn't necessarily a single right answer.