I will be using the Lumix zooms to start with on the AF100. Can I simply zoom in for critical focus?

As far as Im aware most of them dont hold focus when you zoom in and then zoom out (not parfocal).

Steve

I have the 14-140 and it will electronically refocus as you zoom so you can use it by zooming in, focusing, and then zooming out and it will be good enough. It's not parfocal, and you can't really get a good shot while zooming because the focus jumps sometimes, but it works. (Using it with the focus set to activate with button push, not continuous AF.)

From experience I know the GX Vario PZ 45-175 holds the focus but the exposure drops noticeably from f4 to 5.6 if you are at full open and zoom in. It doesn't return to f4 when you back zoom out while in manual aperture. The new 12-35 zoom has reports that in addition to holding the exposure thru the zoom range, which is what it was built to do, it holds the focus as well.