Does the AF speed on the D7000 and up matter for most lenses?

[kcjb]

I assume that when you are using a lens with built-in AF (which appears to be the vast majority), the lens AF motor is used and the camera's is just idle. Is that correct?

I'm looking for compelling reasons to spend the extra $500 to move from a D5100 to a D7000. This particular reason doesn't seem terribly compelling.

 

[n.hubb22]

^^^ I'm curious as well.

 

[KmH]

I assume that when you are using a lens with built-in AF (which appears to be the vast majority), the lens AF motor is used and the camera's is just idle. Is that correct?

Yes, when an AF-S lens is mounted, the focus motor in the lens is used, not the focus motor in the camera body.

I'm looking for compelling reasons to spend the extra $500 to move from a D5100 to a D7000. This particular reason doesn't seem terribly compelling.

Other worth $500 more, compeling reasons to get a D7000:
To just hit the high points

• Multi-CAM 4800DX auto focus module with 39 focus points, 9 of them cross-type focus points
• 2,016 pixel, RGB, TTL exposure metering sensor
• Pentaprism viewfinder w/approx 100% view
• EXPEED 2 Image Processor
• CLS Commander mode
• 12 or 14-bit lossless, or lossless compressed Raw
• Up to 6 frames per second in shutter burst mode.
• Supports legacy Nikon AI and AI-S lenses
• 2 - SD card slots
• Depth-of-field preview
• 1/8000 maximum shutter speed
• many more external controls to minimize menu diving

 

[kcjb]

Thanks!

 

[mjhoward]

KmH made excellent points. I'll add that the bottleneck for AF speed isn't just the AF motor speed. You can take the 24-70 2.8 and put it on a D5100 and it will still focus slower than if you put the same lens on a D3s. Not only do higher end bodies have more focus points and more cross-type focus points, but they have more focus points that are sensitive to smaller apertures.

Understanding Camera Autofocus

If you scroll down to the AF array diagrams, you can wave over the f-stop to see which AF points and what type are active at each aperture. An array like the one depicted for the higher end body means less hunting (especially in low light) and faster subject lock.