Basic questions re using an external mic

[holmes2]

Hello, I recently bought a used Rode Videomic (with Rycote and deadcat) to play around with and see how it differs to the built in mic. I'm new to audio, and have a few quick questions.

1. This Videomic has 3 levels, 0db, -10 and -20db. Unless videoing in a noisy environment like a club or something, I should generally always just use 0db, is that right?

2. What settings in my Canon M should I use to best match with this mic? Sound recording manual or auto? If manual, how far do I set the slider bar from min to max? Should wind filter be off? Attenuator off or on?

3. Do I need to install magic lantern on my Canon M to access some key feature for audio that it doesn't have natively? I'm hoping not, but can do it if I must.

I'm going to a wedding in some weeks time, and would like to do a trial there (I'm not the photographer or anything, but would like to just have the camera on a tripod to capture the event, and give to the bride and groom.) I'm assuming the external mic will do a better job than the built in one? Do the settings I use above depend on how far away I am located, or will the settings work fine whether I am close or at the back? I'm very comfortable setting up the camera for the video with lenses etc, and I know photography but don't know anything about external audio. I don't really want to record separately and combine it in post.

Thank you.

[smrpix]

Every situation is different.

Generally, use manual settings. You want to record as full a signal as you can without over modulating.

Test out the gain settings on your mic and camera in various scenarios.
Listen back to your tests on good speakers or headphones so you know what you are really getting.
Keep an eye on your levels during recording.
Try not to put yourself into a situation where you have to make sudden drastic changes.

Using an external recorder is fine because it usually gives you better options for mic placement. If you're recording a wedding start both recorders and don't turn the camera on and off even if you're resetting. That way you only have to find a sync point once.