There does not seem to be much information available on the D80's Multi-Cam 1000 sensor. I have had a few pictures that are out of focus, even though the focus point is where it should be. At first I blamed the Sigma 18-50mm lens, but now I am beginning to think, it is the AF sensor.
The first issue is that the focus points that are to the left and right of the central area can only detect horizontal lines. I tested this, and found that they simply don't detect vertical lines.
Secondly, the focus central focus area itself is slightly bigger than the bracket displayed on screen. If multiple objects appear inside the area covered, then the camera can end up focusing on the wrong thing.
An out of focus picture is a real disappointment as it is not always evident until you look at the picture at 100% magnification. By then it is too late to fix it. Hopefully as I learn more about how the D80 focuses, I will be able to get more pictures in perfect focus.
I am surprised that none of the D80 reviews really look at its auto-focusing abilities in depth.
Update: I asked Nikon Support about the layout of the AF sensors. The answer I got was this:
The centre AF area is a cross type area. The 2 AF areas above and below the centre area are horizontal AF sensors and all the rest are vertical AF sensors.
This means that the 2 sensors above and below the central sensor can only detect vertical lines, and the rest of the sensors, apart from the central one, can only detect horizontal lines. I have to see if I use this knowledge to get perfect focus each time.