A friend asked me to record an event for him recently and gave me an external mic to use. When looking at the level adjustments on my EM1, I saw there's an option for external and line in, in addition to the built in mic. What's the difference between external and line in? The external mic I was using was plugged into the mic jack and was registering on the "line in" option. Also, is there any way to monitor audio levels while recording video? I would like to be able to see of it's peaking or too quiet and adjust manually.