Exposure modes: M, A, S and P
In short
- In M (manual) you set aperture, shutter speed and ISO yourself.
- In A or Av you pick the aperture; the camera picks the shutter speed.
- In S or Tv you pick the shutter speed; the camera picks the aperture.
- Exposure compensation (+/–) tells the camera to make the next photo brighter or darker.
The mode dial
Most cameras have a dial or menu with letters on it. Each mode decides which settings you control and which ones the camera controls for you. Brand names differ: Canon writes Av and Tv, while Nikon, Sony and Fujifilm use A and S.
P: program
The camera chooses both aperture and shutter speed. You can still change ISO, and on most cameras you can turn a dial to shift the pair (a wider aperture with a faster shutter, or the reverse) while the brightness stays the same. Good for quick snapshots.
A / Av: aperture priority
You choose the aperture, the camera sets the shutter speed. This is the most popular mode for portraits and landscapes, because aperture controls depth of field. Keep an eye on the shutter speed it picks: in dim light it may get too slow to hold steady.
S / Tv: shutter priority
You choose the shutter speed, the camera sets the aperture. Use it when motion matters: sports, pets, moving water. If there is not enough light, the camera may hit its widest aperture and the photo will come out dark.
M: manual
You set everything. It takes a little longer but gives the same result every time, which is useful for night scenes, studio flash, panoramas and anything the meter could misjudge. With Auto ISO switched on, manual becomes a flexible “choose aperture and shutter, let ISO follow” mode.
Exposure compensation
The camera's meter tries to make every scene medium grey. That works for most scenes but fails on very bright or very dark ones: snow comes out grey, a black cat comes out dull. Dial in +1 or +2 for bright scenes, –1 for dark ones. In P, A and S modes, compensation is the quickest way to correct brightness.