Due to the almost non-existent description of the TTL system in the Panasonic manuals, I'm learning its TTL system by trial and error. So far, what I've found is a pretty robust and decent system, although sophisticated algorithm like Nikon's TTL-BL or the all-important FV-lock would really be handy. (Olympus and Panasonic should start to build those into the system if they want to attract more serious strobist.) In any event, I've been tinkering with the three TTL metering on Panasonic. (If I'm not mistaken, the chosen metering for ambient actually is applied to flash too. So, if you chose matrix for ambient metering, the TTL will also meter based on matrix evaluation, even if the camera's ambient exposure is manually set.) The spot metering definitely biases for the focus point, even if the focus point is not at the center of the screen. This is a quick fix for the lack of flash value lock. Since you don't have to get a flash exposure from the subject in the center and recompose, it is as convenient as FV lock in a different way. What about the center-weighted metering though? Does it have bias for the focus point too? I've been doing some experiment but I don't see any difference between center-weighted TTL shots and matrix-metered TTL shots. Nothing comes up on google search. Any body has definitive handle on this?