Thu Oct 03, 2019 8:38 pm
I think most discussions about weak preamps can be explained.
If an audio signal is not very loud, it quickly becomes very difficult to capture usable audio. This applies to all audio recording technologies, be it analogue with tape or digital. This is just how it is. That's why there are Lavalier microphones close to the source, booms with enclosure around the shotgun mic, delicately placed microphones not seen from the camera, wind-shielding fur material, and vocal overdubs in the studio. In general the microphone should be as close as possible to the source, or shielded accordingly. You all know that, but in this discussion I felt it was worth repeating.
When watching movies I often wonder how they got the audio signals so perfectly recorded. This is a science by itself. It is not trivial, these audio guys know their art extremely well.
It is very important that BMD cameras (or any camera with internal microphones) do not amplify the incoming signal too much. If they did, users would complain about distorted audio, which is completely unusable. They would complain about noise. One can boost the signal in post, but then there is still the choice available to re-record in studio environment, or apply noise reduction and noise gate.
Most of us will know well that with analogue gear there is some tolerance because tape allows some over-saturation, while digital recording has no tolerance at all. When the signal is clipped, it is clipped. That's why there are very complicated and sophisticated limiting processing going on in digital recording cameras to prevent going over 0dB. But this is only a help for the (digital) cameraman, in general it is better to record at levels that have some headroom below 0dB.
Capturing good audio is a very complicated thing. Just like capturing images. One can use internal microphones, but one shouldn't expect too much. The same applies to external microphones, one slight mistake and your audio is useless. Know your enemy (the physical laws of sound transmission though a medium, and the limits of digital recording), and it will become your friend.