Except, perhaps, you have one motor instead of one in each and every
lens? Seems more sensible to me... And if you update the motor, you'll
see an improvement for *all* lenses.
If you have an original EOS lens, and buy a new lens, you have just
updated your AF technology.
Not really. You are still stuck with the same in-camera sensor system,
aren't you?
Sure, but you have quite likely updated some of the control circuitry and
are taking advantage of improvements in AF motor technology. If you
have in
camera AF, you are locked out of this.
Yes, but in return for that, you are given the ability to take advantage
of improved AF motor technology *with existing lenses* if you replace
the body.
The most important factor is how efficienty the overall system works.
Lens driven AF is more efficient than body driven AF.
I very much doubt that this holds as a general claim.
Two out of four camera companies disagree with you.
Logically that proves the choice is arbitrary, doesn't it?
Furthermore, I suspect Canon chose in-lens motors because they had
decided that there would be no mechanical coupling whatsoever between
the lens an body, i.e. not based on AF considerations as such. May or
may not have been a good idea; that's really a different discussion.
- T
