Nikon D5500 - Manual (Page 142)

118 P, S, A, and M Modes
Mode A (Aperture-Priority Auto)
In this mode, you can adjust aperture to control depth of field
(the distance in front of and behind the main subject that
appears to be in focus). The camera automatically adjusts
shutter speed for optimal exposure.
To choose an aperture:
1
Rotate the mode dial to A.
2
Choose an aperture.
Rotate the command dial left for larger apertures (lower f-
numbers), right for smaller apertures (higher f-numbers).
Large apertures (low f-numbers, e.g.
f/5.6) blur details in front of and
behind the main subject.
Small apertures (high f-numbers, e.g.
f/22) bring the foreground and
background into focus.
Mode dial
Command dial