AF-S Vs. AF-D

This might be a silly question but it has been bothering me for a while. Say i

have a D80 (although i have D40X) and ofcourse it has an internal autofocus.

Considering there's 2 equal lens (max aperture and focal length), one is AF-S

and one is AF-D. Which one is better? I guess my question is AF-D will be

cheaper since it has no internal focusing so why would anyone pay extra for

AF-S? does it have any advantages in the body that already has an internal auto

focus?

Thanks!

AF-S and AF-D are two completely different things. Many Nikon lenses are both AFS and D.

 

The D means the lens can report focus distance information to the camera, which the camera can then use in determining exposure (especially flash exposure). I think most current Nikon autofocus lenses are D lenses.

 

AFS mean the lens is equipped with a silent wave motor for fast autofocus operation. Nikon lenses that are not AFS are focused by a motor in the camera body. (I understand the D40 lacks this motor and can only use AFS lenses) AFS lens focus faster and quieter that non AFS lens. They are more expensive, but they are usually top end pieces of glass.

 

Internal focus is a whole other feature. An internal focus lens is designed so that it does not change lenght, and the front lens element does not rotate during focusing. Again, this a feature usually found on high end and some midrange lenses that many or may not be AFS.

AF-S means the (auto)focusing motor is in the lens. AF-D lenses do not have focusing motors; they must be focused by a motor in the camera. Optically it does not necessarily matter; but most AF-S lenses achieve focus faster than their AF-D counterparts even on models that have an internal motor.

The D-40 and D-40X do not have focusing motors in them, and will not autofocus any lenses except AF-S, which might motivate some people to pay the difference. HWD

<a href=http://www.nikonusa.com/template.php?cat=1&grp=5&productNr=2170>Here</a> is Nikon's page describing the 18 - 55mm lens, and it mentions the so-called "Silent Wave Motor" in the lens. That motor is what distinguishes the AF-S lenses from other AF Nikkor lenses. <p>

 

That motor is also found on the <a href=http://www.nikonusa.com/template.php?cat=1&grp=5&productNr=2159> 18 - 200mm lens </a> you mentioned, and the <a href=http://www.nikonusa.com/template.php?productNr=2149&cat=1&grp=5>18 - 70mm</a>, and many others as well. <p>

Incidentally, Hugh's answer is also mistaken to the extent that it suggests that a Nikkor lens can be either a "D" lens or an "AF-S" lens, but not both.<p>

 

It's not an either/or proposition. For example, all of the newer G-type lenses are also D lenses, even though they don't contain the "D" initial in their names.<p>

 

For example, the <a href=http://www.nikonusa.com/template.php?cat=1&grp=5&productNr=2139> 70 - 200mm f/2.8 VR lens</a>, a pro-level lens, is all of the following: <p>

 

- a G lens <p>

 

- a VR lens <p>

 

- an AF-S lens <p>

 

- an ED lens <p>

 

- an IF lens <p>

 

- and finally, a D lens -- although as noted it lacks the initial "D" in its name <p>

 

Confusing, isn't it ? Nikon probably could've done a better job of explaining all of this, and naming the lenses so as to make the differences more apparent.

As soon as Nikon runs out of letters they will probably go to Japanese characters. (I have met some of those characters, too.)

A few people have already mentioned focus speed, but you also gain a decrease in noise, and most of the AFS lenses are also M/A which means that they have manual override of focus without having to switch on the camera body. I believe the 18-55 and 55-200 are the only AFS lenses which do NOT have this feature.

 

For the glossary of these lens-related the terms, check out the Nikon Imaging website.

If you have a D80, all other things being equal, I would think you would definitely prefer an AF-S lens. If it was a small lens it might not make much difference. If it was a large lens, it could make quite a bit of difference.

 

If you have an AF-S len, then your camera will focus in a manner similar to the D200, since they share the same autofocus module. If it is an AF-D lens, then the lens will be driven by the motor in your D80, which is one of the areas where Nikon cut corners to make the D80 cheaper than the D200. The auto-focus performance vs a D200 will be inferior. How much?

THAT depends on many factors.