A Little Clarification Please!

[MR.FEESH]

So I'm comparing the Nikon D5000 and the D90 for a good entry level DSLR.  What I need some help on is regarding the placement of the auto focus motor.  
My understanding is that the D5000 requires lenses which have the motor built into the lens itself (Nikon labels those AF-S lenses if I'm not mistaken...?).  The D90 on the other hand has the auto focus motor in the body.  Because the technology used in the bodies is always changing (improving for the most part), I've heard it's always good to spend the real money on sharp/fast/etc glass, rather than jumping for the most expensive body because pretty soon another better one will be released.   If I were to get either the D90 or the D5000, I would be building two different lens catalogs depending on my decision-- if I went the D5000 route, all of my lenses would have motors in them, and if I went the D90 route they wouldn't.  So my impression is that if I ever upgraded to a nicer body down the road, it would most likely already have a motor in it, and if I go the D90 route, I would be able to use all of those lenses on the improved technology of a better body.  If I go the D5000 route, I would need to buy a whole new set of lenses when I upgraded to a nicer body (that presumably has a motor in it already)....is this correct?  If so then wouldn't it make the most sense for me to chose the D90 over the D5000 because the lenses I buy for it will fit perfectly on a nicer body if I decide to get one in the future?

One more question...

Third party lenses like sigma...where is the motor in most of them?  If I wanted to keep my options open I'd like to go with a the body that has the most selection outside of nikkor.

Thanks in advance for your help!!!

Elby

[Tony Beach]

Looks to me like you've done your homework as everything you wrote is correct.   As for Sigma, the HSM models have AF motors in them, and Tokina and Tamron are starting to add AF motors (usable on Nikon's consumer DSLRs) too.  We can expect many of Nikon's non-AFS lenses to update over the next few years to AFS versions, and if there is a successor to the D90 it may not even have an AF motor.  For higher end Nikon DSLRs it is very unlikely that Nikon will lose the built-in AF motor anytime soon, just as those cameras continue to be able to meter on older manual focus lenses.

[Gary Brown]

If I were to get either the D90 or the D5000, I would be building two different lens catalogs depending on my decision-- if I went the D5000 route, all of my lenses would have motors in them, and if I went the D90 route they wouldn't.

No, that's not correct; you wouldn't be building two different lens catalogs.

The only difference is that an autofocus lens without a focus motor (mostly older lenses) will autofocus on the D90, but not on the D5000 (you'd have to manually focus it).

OTOH, an autofocus lens with a focus motor (almost all newer lenses, designated AF-S or AF-I) will autofocus on both the D90 and D5000.

IOW, the cameras don't require different lenses. It's just that if you already have (or choose to buy) autofocus lenses that aren't AF-S or AF-I, then you might prefer the D90 because it can autofocus with them.

[MR.FEESH]

[quote name='Gary Brown' date='Jan 1 2010, 07:18 PM' post='336983']
No, that's not correct; you wouldn't be building two different lens catalogs.

The only difference is that an autofocus lens without a focus motor (mostly older lenses) will autofocus on the D90, but not on the D5000 (you'd have to manually focus it).

OTOH, an autofocus lens with a focus motor (almost all newer lenses, designated AF-S or AF-I) will autofocus on both the D90 and D5000.

IOW, the cameras don't require different lenses. It's just that if you already have (or choose to buy) autofocus lenses that aren't AF-S or AF-I, then you might prefer the D90 because it can autofocus with them.
[/quote

Hmm, sorry if I sound repetitive, but you're saying that an AF-S lens which already has an auto focus motor in it will still work on a D90 or any other body that also has a motor in it?

[Gary Brown]

Hmm, sorry if I sound repetitive, but you're saying that an AF-S lens which already has an auto focus motor in it will still work on a D90 or any other body that also has a motor in it?

Right, the AF-S lenses work on all of the camera bodies, both those that do and don't have focus motors.

[bjanes]

Because the technology used in the bodies is always changing (improving for the most part), I've heard it's always good to spend the real money on sharp/fast/etc glass, rather than jumping for the most expensive body because pretty soon another better one will be released.

Elby, what you say is quite true. In addition to the location of the focusing motor, you should also consider how the aperture diaphragm is controlled and the coverage of the lens, i.e. FX (full frame) vs DX (crop frame).

Currently full frame on Nikon is expensive, but the price may come down. You can use a FX lens on a DX camera, but not the reverse. The FX lenses can work quite well on the crop frame sensors.  The FX telephotos will have more reach on a crop frame camera, while the FX wide angles will not be so wide on the DX body.  I would advise against buying a professional grade DX lens if you think you might eventually migrate to full frame.

Many of the newer Nikon cameras require the use of a G type lens, where the aperture is set electronically by the camera rather than by  an aperture setting ring on the lens. The more expensive cameras can use either the G type lens or the older type with an aperture ring on the lens barrel.