# AF tracking - 11/39/51 points - real world differences



## Caps (Feb 19, 2013)

hi all, 

   I'm wondering what the real-world differences are between the 39 point focus and 51 point focus for action/sports. I've read conflicting opinions about the two - some saying the 39 point (D7000) is just as fast or faster than the 51 point (D300s). 

   Has anyone here used both and can you comment on the actual differences seen from shooting both.


Thanks....


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## kundalini (Feb 19, 2013)

Caps said:


> I'm wondering what the real-world differences are between the 39 point focus and 51 point focus for action/sports. ....


12 points.


My Nikon bodies have 9, 21 & 51 AF points, but 99% of the time I have it set to 21.  I don't shoot a lot of action / sports, but the times I have 21 seems to be fine for me and have set it to 9 just to reduce the amount of AF point adjustment.  Anticipation of the action is the key, methinks.  51 point might be okay with the dynamic tracking.  The best bet is to try them all out and see which one fits you better.


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## Caps (Feb 19, 2013)

_12 points. 
_
Maybe I'm not asking the question correctly. Is there a difference between the different tracking systems in terms of quality? I'm sure it's possible to make different quality tracking systems with missles (the old man was a scientist), so surely its possible with a camera range finder.


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## TheLost (Feb 19, 2013)

The simple answer is:

For Auto Focusing... It gives the camera more choices to focus on.
For User Select Focusing... It gives the human (you) more choices to focus on.

The more complex answer:

Its not about how many points, its about the entire auto focus system.  The Multi-CAM 3500FX system in the D4/D800 is faster and more robust then the Multi-CAM 4800DX in the D7000.  The 51 point system also gives you 15 cross type sensors while the 39 point system only gives you 9.

In real-world-shooting i hit the limits of the D7000's focus system all the time.  Its why LOTS of people have stayed with the D300/D300s and it's Multi-CAM 3500DX AF system (faster and more accurate).



In a nutshell... its the system as a whole and not just the number of points


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## KmH (Feb 19, 2013)

The D7000 Multi-CAM 4800 AF module is newer but only has 9 cross-type focus points, and has a lower light limit of -1 EV.

The older Multi-CAM 3500 AF module has 15 cross-type focus sensors, and also has a lower light limit of -1 EV. Note that Nikon's flagship, pro grade D4, and the prosumer grade D800, both use the newer version of the Multi-CAM 3500 AF module that has a lower low light limit at -2 EV.

Both are phase-detection systems whose speed is limited by the lens focus motor, not the electronics of the focus module. Many of Nikon's fastest focusing lenses are the older screw-drive, AF designated lenses, that rely on the auto focus motor in the camera body.

AF-S lenses don't have a physical connection to that in the camera screw-drive focusing system, and can only use the AF motor in an AF-S lens.


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## Caps (Feb 19, 2013)

Great info guys....thanks.

   I wasn't sure about upgrading to a used D300 (like buying an older outdated computer) but now I'm okay with it.


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