What are the benefits of using a microphone on a boom vs a lav vs on the camera? What are the differences between single and dual-system recording?
Using a mic on a camera is useful when it comes to situations like filming documentary-styled, b-roll, or for a scratch track because it doesn't require syncing and the only set up is turning the camera on, which is important for those types of recording as you may not have the time to set up any other types of microphones. However, doing this usually leads to worse quality audio because the camera operator needs to be closer to pick up good sound, meaning that for shots that are further, the sound will be sacrificed. Using a lav is really good for its subtlety as it is small and can be effectively hidden whilst still picking up good quality sound. For instance, lavs can be attached to people, hidden in their clothes, or planted in the environment in props or when shooting in a car. This means that lavs are very good for narrative filmmaking because it prevents the microphone from being seen and breaking the immersion. However, some downsides are that lavs are very sensitive to clothing rustle so any movement from a laved up actor risks ruining the lav audio. Lavs can also be clipped onto the outside of clothing, eliminating the rustle, which is good for interviews, field reporting, documentaries, and shots with a tripod. Using a boom mic is usually what gets the best sounding audio with much less risks of poor quality compared to the other kinds. As the mic is somewhat directional, it can eliminate some of the background and isolate the subject, making the audio much clearer. The boom pole itself allows for the mic to be as close to the subject as possible, without coming into frame, meaning that you don't have to worry as much about distance to the camera. Some downsides is the fact the boom pole can be quite obtrusive as you have to worry about the shadow, reflections, and if you're in the shot. It's also much harder to move around with making on-the-go shooting much harder. Thus, this is best for stationary settings and narrative filmmaking.
Single-stystem recording is when you connect the mic directly to the camera and dual-system is where you use a separate recording device. Single-system is much simpler and cheaper as you won't have to purchase a recorder and the audio will already be synced in post. However, it is much more limited in the mixing capabilities and sound quality. On the other hand, dual-system recording can give you much more freedom to adjust the audio and also give you better quality sound. The drawbacks come with the cost of buying a preamp/recorder, the added setup, and having to sync up the audio in post.