The following is more likely to be US-specific.
[...]
Any joint copyright holder can grant a non-exclusive
license
(such as CC-BY-SA or the GFDL) to anyone, for any reason, but
the joint copyright holders must share any financial gain they
derive from exclusive use of the work.
In case common sense and a US-specific answer do not satisfy, you can appeal to
the Berne convention, in force in pretty much everywhere. If your cameraman has
any claim at all (!) he is an unidentifiable author. You are deemed to represent
him.
But some Wikipedians like to cross their Ts and dot
their Is, and they
even like to force other Wikipedians to do so. So in some sense it is
useful to think about this for the case of those Wikipedians, just to
get them off our backs.
Vigilance against copyvio is good, but I would have some concerns about
excessiveness in this respect. I guess this follows the same pattern as
vigilance against vandalism.
Regards,
Dan