On Mon, 15 Sep 2008 13:42:32 +0100, Paul wrote:

But, why have a 6 minute limit? What if for example you are shooting an
interview, a speech, a music/theatrical scene, etc. or even a 'special' home
movie? Why the restriction? Surely it's not to allow the sensor to cool
down if you can start recording again immediately?

I don't know how accurate it is, but I've read some accounts in
the DPR forums that at this point the file size reaches 2GB, the
maximum "safe" file size limit for many computers. Nikon could have
used common techniques such as continuing to shoot, using as many
2GB files as needed for a single video (the Zoom H2 does this for
large audio files), but maybe Nikon has that single file limit to
make the non-pro D90 "idiot proof", so an inexperienced user doesn't
completely fill their only 4GB or 8GB card with a single relatively
short video.

You're right about it probably not being a heat restriction, as
some there (DPR forums) that have measured sensor temperatures (one
buys sensors used in cameras that he's designed for other companies)
show that sensors don't significantly warm with extended use,
typically using only about 1/10 the energy used by the LCD display.