I've heard people question before whether or not the GH2 has a fan inside.
After hearing the sound I'm pretty sure I know what it is.
There is a speaker inside, i think behind the panel that the screen lays against when it is closed.
It plays the audio back when you play your video clips.
The sound is crosstalk from the processors etc being amplified and you are hearing it come from that speaker.
You can check this by putting your ear up to the back of the camera in a quiet setting and turning the focus on a fly by wire lens (I'm using the 14-140). You will notice that some positions of focus make more noise than others. It's likely that the audio won't appear in the audio track unless your signal is really low and unlikely that the sound would make it to any mic further than a foot away, so I don't think it's an issue.
However listening to the noise and how it changes, I could see how this might be the same kind of thing leaking into certain iso settings and causing the blue band. Maybe it's just that certain settings emit more crosstalk type noise for whatever technical reasons have to do with the magic that goes on in that processor. (like the way different settings on the focus emit different amounts of sound and are not really linked to where you are on the focus throw.)
Anyhow, just my observations and a guess at what the sound is.
After hearing the sound I'm pretty sure I know what it is.
There is a speaker inside, i think behind the panel that the screen lays against when it is closed.
It plays the audio back when you play your video clips.
The sound is crosstalk from the processors etc being amplified and you are hearing it come from that speaker.
You can check this by putting your ear up to the back of the camera in a quiet setting and turning the focus on a fly by wire lens (I'm using the 14-140). You will notice that some positions of focus make more noise than others. It's likely that the audio won't appear in the audio track unless your signal is really low and unlikely that the sound would make it to any mic further than a foot away, so I don't think it's an issue.
However listening to the noise and how it changes, I could see how this might be the same kind of thing leaking into certain iso settings and causing the blue band. Maybe it's just that certain settings emit more crosstalk type noise for whatever technical reasons have to do with the magic that goes on in that processor. (like the way different settings on the focus emit different amounts of sound and are not really linked to where you are on the focus throw.)
Anyhow, just my observations and a guess at what the sound is.
)