Focusing with the center AF sensor only and recomposing will generally put the plane of focus behind the intended subject (assuming the lens does not have an ex

Focusing with the center AF sensor only and recomposing will generally put the plane of focus behind the intended subject (assuming the lens does not have an extraordinary degree of field curvature). The geometry is easy to see if you remember that your focus distance is the distance from the sensor/film plane to the subject, not the distance from the lens to the subject. The problem is more noticeable with a wider lens, a larger aperture setting and a closer subject, but it's always there. That's why Hasselblad (who only offer one AF point in the H4D camera system) has incorporated positional sensors and focus correction in their latest models. If your camera offers the option, choose a focusing composition that will put your subject as close as possible to its final position in the picture and use the focus point closest to that position.