Lenses & optics - fhe basics

Lenses & optics - fhe basics

Apart from the CCD in a digicam, the lens is the most important element to ensure a quality image. Most digicams have zoom lenses which allow you to vary their focal length from wide-angle to telephoto. Focal lengths are indicated in millimetres.

On conventional 35mm cameras, lenses shorter than 50mm are considered wide-angle while longer focal lengths are telephotos. A 50mm lens is considered “normal” because it sees the scene in the same proportions as the human eye does. Although some DSLRs have full frame sensors, the equivalent on most digicams would be a 6 or 7mm lens, as most CCDs are much smaller than 35mm film. For clarity purposes however, we will refer to focal lengths as compared to 35mm because CCDs on digicams are not uniform in size and their focal lengths and angle of view vary widely.

Your choice of lens depends on the subject in your image. Wide-angle lenses have a wide angle of view and greater depth of field which is perfect for sweeping landscapes.

Portraits or close ups would require a telephoto. Their angle of view is narrower and objects in a scene appear larger. Should you want to get very close, macro mode on your camera greatly magnifies the subject but depth of field will be limited.

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