First of all we will get focusing out of the way. With focusing you have two choices, autofocus (AF) or manual focus.There are different types of autofocus systems but basically you either have it turned on or you don't. Although autofocus is pretty standard on new 35mm/APS cameras these days not having this feature isn't really a drawback. AF can be quick, convenient and fairly reliable but is by no means essential.
The area where you will find most automation is in the control of exposure. More specifically the control of the aperture and shutter. These different types of automation are usually referred to as 'modes'. Most modern cameras are 'multi mode'. Basically there are four modes you can work in.
- Manual.(M) You set the aperture and shutter yourself.
- Aperture Priority.(A) You set the aperture and the camera will automatically select the corresponding shutter speed.
- Shutter Priority.(S) You set the shutter speed and the camera will automatically select the corresponding aperture.
- Program.(P) You point the camera and it will select a suitable aperture and shutter combination.
- Action mode.
- Landscape mode.
- Portrait mode.
- Close-up mode.
- Fill-in Flash mode.
- Night mode.
An auto camera may simply select a shutter speed to match a pre-set aperture value or it may perform a complex decision making task involving information regarding the type of subject , lens attached and other data you may input. After all this calculation the camera will then adjust the shutter and aperture. And that,basically, is all they do.