Digital photography, digital cameras and pictures.

Lenses for digital cameras

There are two major components of digital cameras that play a big part in image quality – the image sensor and the lens. Get the best you can afford -- good quality lenses are essential for getting the most out of digital photography.

Lenses are available in various focal lengths which determine field of view and depth of focus. As they become longer they can focus on smaller areas but require more precise focusing to obtain a sharp image. Longer lenses are also more susceptible to movement and will likely blur images if the camera is moved during a shot.

Long lenses are sometimes called telephoto lenses. Because of their reduced field of view, the images shot with telephoto lenses are magnified compared with shorter lenses. Similarly, shorter lenses give a wider field of view, so very short lenses are called wide-angle lenses.

A 'normal' lens is one that produces an image similar to what the human eye sees. There is no standard length for a normal lens because field of view is directly connected with the size of the image sensor that captures the photo. A 50mm lens is considered normal for traditional 35mm cameras but digital image sensors are much smaller than a frame of 35mm film, so shorter lenses on digital cameras will capture the same field of view as the 50mm lens on a 35mm camera. The specifications of a digital camera lens will often include a reference to how the focal length compares to a 35mm camera.

Almost every digital camera has an optical zoom function that changes the focal length of the lens. They are rated as a multiplier – a 3X zoom will enlarge or reduce an image by 3 times from the longest to the shortest setting.

Some cameras are also equipped with a digital zoom. These work by cropping the image digitally and then spreading the result over all the photosites on the image sensor. This is inferior to optical zoom and should not be used. Better results can be obtained by editing the photo using computer software.

Most digital cameras in the mid-range and better have the ability to add lens converters. These give you more options for digital photography by allowing you to attach various types of lenses and filters.

In addition, many digital cameras can accept lenses made for film cameras. Because of the difference in size between film and image sensors, however, these lenses do not produce the same results as with film cameras. A telephoto lens designed for film will have a larger magnifying effect, and a wide angle lens will have less effect on a digital camera.

Lenses are quite expensive. They should be kept in cases and covered with caps when not in use. Most lenses come with caps but you may have to buy extras in case they are lost. They are widely available and fairly inexpensive.

Lens hoods are useful for controlling the amount of light entering the lens. They result in images that have less contrast – useful for some outdoor situations.

Lens cleaning kits are available but should be used as infrequently as possible. Avoid touching the lens with your fingers as the oils in your skin can cause permanent damage to the lens coating. Wipe fingerprints with a soft cloth but first remove dust particles with a blower. Larger dust can be removed with a soft brush.

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