AF-D = no need for lens micro adjustment?

Started Feb 9, 2013 | Discussions thread
IanML Senior Member • Posts: 1,653
Re: Sorry folks!

JohnD2000 wrote:

As I understand it, the on-sensor AF points don't actually focus, as such. They track the subject and tell the off-sensor AF points where it's heading. That is, they're communicating with the main AF sensor, rather than moving the lens itself.

In practical use, AF-D works very well compared to AFC. At least that's my experience. But I certainly haven't had to reset my MFA settings, or had any ill effects since the update.

Yes, my understanding is that the data from the on-sensor points is used to generate "range rate" information, to improve the focus tracking by helping to predict which way to move the focus, and how fast to do so.

Without such information, precise focus tracking of a subject which is moving in range would not be possible, as there would always have to be an error between the required focus position and the actual position at any time, in order to make the focusing motor move, i.e. a lag would be present.

Sony use the term "depth" (hence the "D"), and I interpret that to mean range (distance from camera to subject).

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