It is good to remember that a digital camera is a lot like a film camera, but it uses a sensor and a memory card in place of film. When you take a picture, a digital shutter opens and exposes the sensor to light. The sensor reacts to the light, and the memory card stores the resulting picture.
The light that hits the sensor determines virtually everything about the picture. Your camera may be able make some adjustments, but it has to work with the amount and type of light that it receives. You can control how the light hits the sensor with three settings:
- The focus adjusts the lens in relation to the sensor, making sure that the light converges on the sensor's surface. Most digital cameras have an automatic focus feature, but a few focus manually and have interchangeable lenses.
- The aperture, measured in f-stops, determines how wide the shutter opens. A wide opening lets in more light, and a narrow opening lets in less. Higher f-stops mean that the opening is smaller, and lower f-stops mean that it is larger. The aperture determines the picture's depth of field, or how much of the picture is in focus. At low f-stops, the foreground of the picture will be in focus while the background is out of focus. At high f-stops, objects in both the foreground and background are in focus.
- The shutter speed determines how long the shutter is open. The longer it's open, the more light will hit the sensor. If you or your subject is moving while the shutter is open, the image will be blurred.