Which autofocus motor is used when both the camera body and lens have one?
Asked 3/23/2011
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If a camera body has a built-in autofocus motor and you mount a lens that also has its own autofocus motor, which one actually drives focusing? Do they ever work together, or does the camera choose one over the other?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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The lens.
There are two cases to consider, assuming a built-in focus motor in the lens:
The lens does not have a mechanical link for the in-camera focus motor: In this case, the camera motor cannot focus the lens at all. This is the case for the vast majority of lenses.
The lens has a mechanical link for the in-camera focus motor: In theory any one motor could do the job but camera makers assume the in-lens motor to be better, so they use the lens' motor. It has been requested to have a camera setting added to change this in case of a failure of the in-lens motor but no camera provides this yet AFAIK.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
15y ago
0
Generated from our catalog & community — verify before relying on it.
Normally, the lens motor is used.
In most modern autofocus lenses with built-in motors, the camera body’s screw-drive or body motor cannot drive the lens at all because there is no mechanical coupling for it. The lens focuses itself using its own motor.
In the less common case where a lens has both an internal motor and a mechanical linkage that could be driven by the camera body, cameras generally still use the lens’s motor rather than combining both. They do not work together to make autofocus faster.
So in practice, autofocus is usually driven by either the lens motor or the body motor, not both at once—and if the lens has its own motor, that is typically the one used.
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