Buying a digital camera Part Two - Glossary of terms

Aperture

An adjustable opening through which light enters through the camera’s lens. The larger the aperture is, the greater the camera's photosensitivity. A smaller aperture, however, gives greater depth of field to a picture. The aperture setting is called the f-stop. A small aperture has a relatively high f-number, such as f8 or f11, and a larger aperture has a smaller number, such as f2.8. The aperture setting must be balanced against the shutter speed. The faster the shutter speed, the larger the aperture must be, and vice versa, to admit the right amount of light to the image sensor for proper exposure. These adjustments are done automatically by the camera or manually by the operator.

Compression

A process that reduces the amount of data representing an image so that the file takes up less space in your camera, memory card, or computer. Smaller files are quicker to use for e-mail and on the Web. When a file is too compressed, however, image quality can seriously suffer.

Depth of field

Indicates how much of a scene will be sharp and in focus. A greater depth of field implies an increased distance between well-focused background and foreground, with everything in between properly focused. A narrow depth of field concentrates the area of sharp focus within a small range, based on the main subject's distance from the camera.

For instance, if your subject is standing in an open field, using a narrow depth of field will make most of the scene in front and behind look blurry; only the main subject will be focused. This effect is achieved when using long zoom lens. Using a wide-angle lens will produce a greater depth of field, thereby keeping the whole scene in focus.

Image sensor

The semiconductor chip or Image Sensor is what captures the photographic image. It collects the light of a scene or subject, which it turns into digital data that we see as a photo in the camera or on the computer. There are two main types of image sensors CCD (charge-coupled device) and CMOS (complementary metal-oxide semiconductor). The CCD is the most popular. CMOS is used in very low and high end cameras.

Interpolation

A process that increases image file size and can take place either in the camera or by computer software. Interpolation is used to magnify a picture but does not improve image quality and in fact it can decrease sharpness.

LCD viewfinder

A small screen on the back of a camera that displays what the lens sees. It is used to compose the picture, choose settings, focus and frame an image in macro mode. It is also used to view photos stored on the memory card.

Mega pixel

A measure of a digital camera's resolution. A three-mega pixel rating means that the camera can capture up to 3 million pixels, or points of data.

Memory card

A removable storage device that holds the images a digital camera captures. It is a good idea to have an extra one on hand so that when one card is full it can be swapped for another allowing you to continue shooting.

Pixel

A point of data in a digital image; the word is short for picture element. A digital camera's resolution is a measure of the number of pixels it can capture on its image sensor.

Shutter speed

A measure of how long a camera allows light to fall on the image sensor (expressed as a fraction of a second). Though some digital cameras have both electronic and mechanical shutters, inexpensive models will utilize an electronic shutter to turn off the photosensitivity of the image sensors.