FYI, I also notice ABL (or something very similar). It's most annoying when the amount of light in an image changes, e.g. panning across an ice hockey rink and bringing more (dark-clothed) spectators into the image. As the overall luminosity of the image goes down, it looks like more power is put into the whites, and they noticeably change hue from a grey to a white. When there's any fast action going on, it can be very disruptive, because it ends up as flickering
There is also the issue of a full screen of what should be white (some commercials which are a white background with a small amount of text) which ends up grey.
It's very frustrating because the picture quality is otherwise outstanding.
Am just plucking up the courage and willpower to contact Panasonic and go through a lengthy process which will probably result in having to go through the process of researching a new TV. Again.