Nikon D90 Getting Good Results with Autofocus, Example Subject is half in h the shade, Lens hood

AGetting Good Results with Autofocus

Autofocus does not perform well under the conditions listed below. The shutter release may be disabled if the camera is unable to focus under these conditions, or the in-focus indicator (J) may be displayed and the camera may sound a beep, allowing the shutter to be released even when the subject is not in focus. In these cases, rotate the focus mode selector to M and use manual focus (pg. 59), or use focus lock (pg. 57) to focus on another subject at the same distance and then recompose the photograph.

There is little or no contrast between the subject and the background.

Example: Subject is the same color as the background.

The focus point contains areas of sharply contrasting brightness.

Example: Subject is half in h the shade.

The focus point contains objects at different distances

from the camera. Example: Subject is inside a cage.

Background objects appear larger than the subject. Example: a building is in the frame behind the subject.

The subject is dominated by regular geometric patterns. Example: A row of windows in a skyscraper.

DThe AF-Assist Illuminator

The subject contains many fine details.

Example: A field of flowers or

other subjects that are small or lack variation in brightness.

If the subject is poorly lit, the AF-assist illuminator will light	AF-assist illuminator
automatically to assist the autofocus operation when the shutter-
release button is pressed halfway. The AF-assist illuminator will not
light in l, or m modes or if Off has been selected for Custom Setting
a3 (Built-inAF-assist illuminator; pg. 174). The illuminator has a
range of about 0.5–3.0 m (1 ft. 8 in.–9 ft. 10 in.); when using the
illuminator, use a lens with a focal length of 24–200 mm and remove
the lens hood.

ASee Also

Custom Setting d1 (Beep; pg. 180) can be used to turn the beep speaker on or off.

55