Some days ago I had to help a friend to interface several microphones to a Canon camcorder microphone input. I had interfaced earlier years ago microphones to several prosumer and professional video cameras, but I though it would be a good idea to do a Google search to check what is said on interfacing to Canon cameras.
When I did a search I found a good web page on camera microphone interfacing: Microphone Adapters for consumer camcorders (I know would be able to trust the information on that page because I had earlier good experience on ComClone2 project from same designer). Microphone Adapters for consumer camcorders has this nice plan for interfacing XLR microphones to video camera:
The capacitor should have capacitance something between 1 to 5 microfarads. This looked like a good plan. The question mark was if the dynamic mics had enough output signal to be useable with the camera mic input that was designed for electret capsules (which have typically considerably higher output level than dynamic microphones). It was impossible to test because at the moment I did not have access to that camera. There seems to be commercial adapters for adapting microphones to video cameras that include also amplifiers like ones shown in this video:
I ended up planning an approach which could be easily adjusted on the field when all equipment are there. The approach is quite traditional audio application where the microphones are connected to a small mixer, and the output from audio mixer is connected to video camera input. I made the connection from the mixer main output to camera mic input using a pair of DI unit boxes: those convert line level audio signal from 6.3 mm plug output on mixer to mic level output on XLR connector plus provide transformer isolation for the signal (very often needed to avoid ground loop humming).
I wired the mic signal from XLR outputs directly to 3.5 mm plug (I had such cable already made). In this specific application I could live without the capacitors, because the specific DIY DI unit could handle few mA of DC on it’s output without a problem to sound quality (not all DIs can do this, but my my old trusty DI box with heavy transformer can do that). I tested this approach without video camera by connecting the output to PC mic input (close enough to video came mic input characteristics on many cases). I expect the things go smoothly with the real camera.