Why do lenses need AF calibration?

Started Oct 15, 2003 | Discussions thread
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Radu Tenenbaum
Radu Tenenbaum Senior Member • Posts: 2,880
Why do lenses need AF calibration?

I've read lots of threads about needing to send body AND lens to Canon for AF calibration, but I don't understand how the lens could be out of calibration. After all, isn't the AF system a closed loop system where the focus is adjusted until the body detects optimum sharpness?

Also, can someone explain what is involved in performing the body's AF calibration? Is it firmware or mechanical?

Sorry if this information has already been posted, but there are so many posts on this topic that it's hard to do a specific enough search to get me these specific answers.

Radu

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