Nikon D5300 - Manual (Page 111)

91 P, S, A, and M Modes
Autoexposure Lock
Use autoexposure lock to recompose photographs after using M (Center-weighted
metering) and N (Spot metering) to meter exposure; note that autoexposure lock is
not available in i or j mode.
1
Meter exposure.
Press the shutter-release button halfway.
2
Lock exposure.
With the shutter-release button pressed halfway
(q) and the subject positioned in the focus point,
press the
A (L) button (w) to lock exposure.
While exposure lock is in effect, an AE-L indicator
will appear in the viewfinder.
3
Recompose the photograph.
Keeping the A (L) button pressed, recompose
the photograph and shoot.
A
Adjusting Shutter Speed and Aperture
While exposure lock is in effect, the following settings can be adjusted without altering the
metered value for exposure:
Mode Setting
Programmed auto Shutter speed and aperture (flexible program; 0 84)
Shutter-priority auto Shutter speed
Aperture-priority auto Aperture
The metering method itself can not be changed while exposure lock is in effect.
Shutter-release
button
A (L) button