Nikon D40 Guide User Manual page 58

Autoexposure Lock _ AE-L/_ ]
if tile subject is not in tile metered area when center weighted or spot metering is used,
exposure will be based on lighting conditions in the background and the main subject may
not be correctly exposed. This can be prevented by using autoexposure lock.
1 Select mode P, S ,or Aand choose center-weighted or spot metering (exposure lock has
no effect in mode ivl).
2 Position the subject in the selected focus area (when using
center weighted metering, position the subject in the center --
focus area). Pressthe shutter release button halfway and con _ lr
firm that the in focus indicator (o) appears in the viewfinder.
Then, keeping the shutter release button pressed halfway and _w_ _,
the subject positioned in the selected focus area, press the AE-
L!AF-L button to lock exposure.
While exposure lock is in effect, an ELindicator will appear in E@ .
the viewfi nder:
Keeping the AE-L!AF-L button pressed, recompose the photo
graph and shoot.
46
Adjusting Shutter Speedand Aperture
While exposure lock is in effect, the following settings car/be adjusted without altering the metered
value for exposure.
Mode Setting
Programmed auto Shutter speed and aperture {flexible program; _ 40)
Shutter-priority auto Shutter speed
Aperture priority auto Aperture
The new values can be confirmed in the viewfinder and shooting irfformation display. Note that the
metering method can not be changed while exposure lock is in effect (changes to metering take
effect when the lock is released.
This option controls the behavior of the AE-L/AF-L button.
_ 13iAE Lock ( _ 77)
This option controls whether the shutter-release button locks exposure.
Reference: P ,S,A, and M Modes/Exposure