I've been using the older model ZS19 for a little over a year and have been pretty happy with the results generally. It's not great in low light, but besides that it has suited my personal needs as a beginner point and shoot to complement my audio.
Just to jump on your first question, the exposure settings can't be changed
during recording, but can obviously be changed any time in between. The camera has a nice 'preview' exposure rating if you press down the 'take picture button' half way (is that called something, because I feel very stupid right now not knowing what that is called edit: ah, shutter release. yahoo answers comes through again).
I have not researched much into the video world, but what I've found from basic information and trial and error is that
ISO,
f-stop and
shutter speed are the main components to control when recording. I set my ZS19 to manual control and change the f-stop and shutter speed to fit every show. I keep the ISO at 400.
The F-number (
http://en.wikipedia.org/wiki/F-number) controls aperture size. Basically the
smaller the F-number the
more light it lets in (like your pupil, see wiki diagram). The F-number also has something do with depth perception of the picture as well. The
higher the F-number the
more accentuated the 3-Dness of the video will be (I think).
The shutter speed is a fairly obvious one I feel. The longer the shutter stays open, the more light it lets in. I'm fairly certain it's measured it seconds and fractions of seconds, so the lower the fraction > the slower the shutter speed > the more light gets in.
My own personal clearly uneducated anecdote: I set the ISO to 400. Don't personally go lower than 1/60 on the shutter speed. F-number is usually somewhere in the middle. 5? Maybe? I don't know. Adjust for every show, every room, every different light rig.
http://electronics.howstuffworks.com/cameras-photography/tips/how-to-know-what-f-stop-to-use.htmFor whatever it's worth for, here are videos I've shot with the the ZS19 and the above knowledge (or lack there of):
https://www.youtube.com/channel/UC3K7-3LJds8BtTi1aIV68gA/videos