Nikon D40 Guide User Manual page 39

Getling Good Results wilh Aulofocus
Autofocus does not perform well under the conditions listed below. If the camera is unable to focus
using autofocus, use manual focus (_ 28) or use focus lock (_ 26) to focus on another subject at the
same distance and then recompose the photograph.
The focus area contains
objects at different distances
from the camc>m (_W.,the sub-
ject is inside a _-oge).
ground).
The subject is dominated by
rc>gular geometric pattems I_1 I _F_
(e.g., a row of windows in a
skyscraper).
The subject appears smaller
than the> focus area (e.g., focus
area contains both fore-
ground subject and distant
buildings).
Th_ "_fOCUS area contains areas
of sharply contrasting briqht-
ness (e.g., the subject i_ half in
file shade).
The subject contains many
fine details (fW., a field of flow-
ers or other subjects that am
small or lack variation in
brightness).
Reference:Moreon Photography(AllModes)/Focus 27