Autofocus Question

[McLovin]

Hey guys,

I am looking into getting a DSLR camera for the first time and I'm particularly interested in the Nikon line (trying to decide between a D40 or spend a bit more and get a D80 right off the bat).

Anyways, since Nikon (and I guess other brands too) have autofocus built into the lens now, I have a question about that autofocus.

What happens when both the camera and the lens itself have autofocus built in? Will it automatically choose the faster method, or will it just use both and be twice as fast? And which autofocus is "better", camera body or lens?

Thanks!

[ashley_sue07]

sorry Mclovin wish i could help but i have no idea (since i have a cheap camera .....) Im sure someone here would have the answer for ya.

[oldfireguy]

I believe the AF functions on the Nikon DSL's are all built into the lens. Honestly I'm not quite catching what you mean by AF functions in the body. The camera and the lens work together as a team of sorts. If you look at the back of a AF lens you will see contact points that connect to the camera when the lens is put on. A non AF body will not focus an AF lens, it has to be done manually just as a non AF lens will not focus on an AF body. Confused? I am.

[McLovin]

Well I guess this is mostly referring to Nikon cameras, but I'm talking about how some of the complaints of the D40 are that it lacks autofocus (so you have to have a lens that will do the autofocusing for you), whereas a D80 has autofocus features in the camera body itself.

So when you put an AF-S lens on a D40, you will get the autofocus feature which you wouldn't get with a non-AF-S lens. But now what happens when you put an AF-S lens onto a D80, which does have autofocus features already built into the camera body, and now has the autofocus features built into the AF-S lens?

Sorry I'm not explaining very well, I'm new to this stuff!

[oldfireguy]

OK I got ya now. I pulled this off B&H.

Auto Focus - Silent Wave (AF-S) is a type of focusing motor used in many of Nikon’s AF-Nikkor lenses. The AF-S motor provides faster and quieter focusing. AF-S lenses also have an "A/M" mode selector which allows the user to switch from automatic to manual focus with almost no lag time.

Some older AF cameras are not fully compatible with the AF-S function. With these models, AF-S lenses will have to be focused manually. Incompatible models are: N60, N55, N8008/s, N6006, N5005, N4004 & N2020.

As I read this it will work the same on any Nikon besides those mentioned. I use Nikon for both film and digital but don't have any AF-S lenses.

Hope this makes sense.

[McLovin]

Thanks for the info, oldfireguy. Also, if anyone else more about this and what I'm talking about, feel free to add.

[cadwell]

OK. Once upon a time when Nikon decided to add autofocus to its SLR cameras it decided that the way to do that was to put the focus motor in the camera body and use a cam connected to the lens in order to make the lens focus. A few years down the line Nikon then decided that it was better to have the focus motor in the lens and simply provide electrical power from the body.

For a long time Nikon supported both mechanisms. Their dSLR bodies would be capable of providing electrical power to drive in-lens focus motors and they also had an in-body focus motor to support older cam-driven lenses.

The Nikon D40/D40x and now the D60 are the first Nikon cameras to abandon support for the old cam based mechanism and have no in-body focus motors. They can only autofocus with lenses which have their own built in focus motors. These are Nikon AF-S lenses, Sigma HSM lenses and possibly some others from third party manufacturers.

Lenses only have one focus mechanism. They either need the focus motor in the camera body (which the D40/D40x/D60 lacks) or they use their built in focus motor. There's no decision to be made and no lens has both mechanisms.

[yorkshireman]

........ and there you have it - thanks Cadwell - just looked at your gear list - boy is that impressive

[McLovin]

That clears it up. Thanks for the explanation cadwell!