D800 AF during video ?? Any threads/tutorials

In the first month with my D800...and first time shooting video with a DSLR. So far my AF in picture mode seems fine, pretty much what I have worked with with my D2X. The AF during video is more problematic...with my old lenses anyway. Especially with my 600MM (non VR), it seems very rare that the focus "locks on" and stays on...seems to drift and then re-search every 2-3 seconds...which mades for noisy audio and shimmering blurry video. With my other lenses it seems not quite as bad...mostly because the focus is not so critical...but still too much searching.

A search does not turn up a thread on this. Anyone have any suggestions? Are there any tutorials or other info sources on the D800 AF in video mode?

Thanks.
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Peter Patricelli
http://www.flyfishingfotography.com