Opinions vary greatly among sound engineers on the best method and equipment for recording audio with a DSLR. You've likely seen many videos that use a lavalier microphone — the small piece that clips below the collar of the talent's shirt. Lavaliers come in both wired and wireless options. However, lavaliers can be a bit obtrusive both for the talent (who has to have a wire threaded down his or her shirt) and for the viewer (who has to see a microphone for the whole video).
A note about shooting with two cameras: Your editor will need to sync the footage between the different views. To help them do this, clap your hands loudly in the view of both cameras right before you ask the first interview question … yes, just like an old fashion clapboard. Modern editing software has auto-sync features, but this loud clap will help you initially line up the clips.
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