Heeft vooral met contrast te maken. De AF sensoren werken vooral als een contrasterende lijn haaks op de sensor staat. Door nu sensorvelden samen te voegen ontstaan grotere velden die sneller die contrastverschillen zien. Een bewegende contrasterende lijn blijft langere tijd in een (groter) sensorgebied.
In this pic, only sensor 1 would provide useful focus info by virtue of having some pixels in sharp contrast.
Remember that the sensor only sees a straight line. It is one-dimensional.
Sensor 2 in the pic would see all white.
Sensor 3 would see all grey.
Sensor 4 would see all black.
BRON :
http://www.focustestchart.com/chart.html
Normal Zone 11 Area Focus mode
Wide Zone 7 Area Focus mode
The D200 has two AF area modes; Normal Zone (11 area) and Wide Zone (7 area), as shown in the diagrams below. In Normal Zone mode you can select from any one of the eleven areas and the camera will focus on the center of the selected area, this mode is generally used for mostly static subjects. In Wide Zone mode you can select from any one of seven areas which cover a wider area of the frame, this mode is more useful to focus on the general area of a moving subject.
BRON :
http://www.dpreview.com/reviews/nikond200/page4.asp
! Moet je wel eerst 10 keer (her)lezen voordat je snapt wat er staat en wat de toepasbaarheid is.
