another way to do that is via a DI box. like this:

Behringer ULTRA-DI DI100 at DV247.COM

Plug the line-level output from your desk into the line in on the DI and then take the XLR out which is at mic level and plug it into your camera mic in. (You will need to get a cable that does XLR to whatever the camera mic in is)

It also has a couple of PAD buttons in case your line out is really hot.