The iris control on these cameras is very hit and miss, in my experience. I've even returned one camera to the repair centre and they replaced it with another camera. I mainly use the Panasonic Lumix G Vario 7 mm to 14 mm f4 on the camera. The only exposure control is by pressing the 'IRIS' button on the back of the camera. This sets an entirely random aperture setting on the lens that relies on the exposure metering system built into the camera body. Getting the exposure correct is very much a 'hit or miss' experience. The viewing screen cannot be relied on as a tool with which to judge the exposure as the brightness can be adjusted to suit the ambient lighting conditions.
Focussing is also problematic with this (and other auto) lenses. Pressing the 'FOCUS' button is very 'hit or miss'.
I've been so disenchanted by this camera that it will have to go in the bin soon - after waiting 7 months for it to arrive after ordering it on the first day it was announced. Image quality may be good - but only if you can set-up the camera correctly! Everything is just guess work with this camera.
Apart from using fully manual lenses (I don't know of any that are as wide as the 7 mm of this lens), how does everyone else get round these two problems?