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