The viewfinder is located at the top of the back of digital cameras, and you look through it to compose a scene.
Keep in mind that not all digital cameras have a viewfinder. Some point and shoot, compact cameras don't include a viewfinder, meaning you must use the LCD screen to frame a photo.
With cameras that include a viewfinder, you almost always have the option of using the viewfinder or the LCD to frame your photos. The viewfinder drains less power and allows for better stability than using the LCD.
There are three different types of camera viewfinders.
- Optical viewfinder (on a digital compact camera). This is a relatively simple system where the optical viewfinder zooms at the same time as the main lens. Its optical path runs parallel to the lens.
Viewfinders on compact, point and shoot cameras tend to be quite small, and they often only display around 90% of what the sensor will actually capture. This is known as the "parallax error," and it is most obvious when subjects are close to the camera. In these situations, it is more accurate to use the LCD screen.
- Optical viewfinder (on a DSLR). Because DSLRs use a mirror and a prism, there is no parallax error and the viewfinder displays what will be projected on to the sensor. This is called "through the lens" technology, or TTL.
The viewfinder also displays a status bar along the bottom, which shows exposure and camera setting information.
- Electronic viewfinder (on a digital compact camera). The electronic viewfinder, often shortened to EVF, is also a TTL technology.
It functions in a similar fashion to the LCD on a compact camera, and it shows the image being projected onto the sensor by the lens. This is shown in real time. Technically, it is a small LCD, but it replicates the effect of the viewfinders found on DSLRs. An EVF doesn't suffer from parallax errors.