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This might be a stupid question, but what is the difference?

I use AF-area mode "dynamic area" ... and then i select middle AF point and lock it with the lock switch (above the delete button.) I do this so that on the odd occasion I can unlok and change AF point.

What is the point of having the "single area" AF area? (when it can be done by simply selecting the middle AF point in dynamic)

I only thought of this question as Ive read that the firmware 2.0 speeds up AF in dynamic area mode, but apparently not in single area AF mode.

Have never used the third "closest subject" mode, but thats self explantory.

In Dynamic Area AF, the D70 will track moving objects and continually refocus. It will start focusing using the sensor you have selected, but may move to another. You can also release the shutter at any time, whether the camera has achieved a focus or not. I don't think that the focus lock will alter this behaviour.
In Single Area AF, focus will only use the selected focus sensor. You will not be able to depress shutter unless the camera has achieved focus.

Even in dynamic mode AND in AF-C focus tracking, it strictly obeys whcihever AF point i have selected, never seems to use any other AF points

Or perhaps you mean that in AF-C mode, and with dynamic mode, it will initially lock on middle AF, but then intelligently track a subject across other AF points? ... have never seen it do that.

IN AF-S and dynamic mode, with a point selected (doesnt have to be locked, the lock switch just prevents you accidently changing your AF point.) ... it still ignores all other AF points.

http://forums.dpreview.com/forums/read. ... e=13519350

This thread shows a good example.

The dog wandered from the camera's centre AF point into one of the side AF points. The camera realised this and switched AF points to track the dog. This dynamic shifting of AF point to guess the position of the moving subject was what Nikon documented as having improved in version 2 firmware. However, there has been many reports of users having experienced better AF acquisition overall - far too many IMHO to coincide with placebo or other 'imagined' improvements.

yeah so its kinda like auto-invoking of AF-C even when in AF-S mode (ie, ive selected middle AF point, but if it things my 'subject' has walked to the left of frame it will refocus on that AF point, which may well be closer to me if its walking toward me and to my left.)

Yeah, sorry, misread your original question.
But, my answer was still partly correct, even if I had the bull by the t%t!

D70 manual, Page 67:
Dynamic - Camera uses information from multiple focus areas to determine focus. If subject leaves selected focus area even briefly, camera will still be able to focus.
Single - Camera focuses on subject in selected area only.

Your method may have some advantages, especially if subject is not static.

cool cheers , ive never seen it actually do it (regardless of AF-S vs AF-C) .. nice to know it has some smarts if the right situation arises i guess.