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by Lars Kotthoff

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AF-D lenses use the body motor, so how is this possible?

Of course, I'm talking about lenses with the same focal length & min distance.

For example - Nikkor 80-200 AF-D - the 2 ring version and the push-pull version.


A bit more: I'm currently reading a lot (a lot lot) information for Nikkor 80-200 AF-D and I was wondering which one to get. The push-pull version can be found for about $400 on eBay, while the two ring version is about $700 and the difference is huge.. I like the 2 ring version very much, but I'm not sure it's worth it. At most forums, people say the only difference is the focusing speed (really?)
I have D7000, if it matters.

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1 Answer 1

up vote 4 down vote accepted

Yes, different lenses can definitely have different focus speeds. When focusing, a specific group of elements are typically moved.

The size and weight of a group of elements varies with a given lens formula. When focusing a small prime with only a few elements/groups, the AF motor isn't going to have to move much weight. Zoom lenses almost always have more complex groupings of elements, which undoubtedly makes them heavier and therefore takes more work to move. Additionally, the distance the elements need to move will effect how fast focus seems to be achieved.

Additionally, the focus motor's strength and speed varies with camera body. Simply, better cameras have better focus motors. Smaller and lighter lenses will gain no advantage from this, but larger and heavier lenses will.

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