What is focal length?

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In the field of photography, focal length is one of many terms that is commonly used among expert photographers and enthusiasts.  Many people may also encounter this term when reading labels for digital or SLR cameras.  Focal length is basically the length or distance from the camera’s lens to its focal point.  In technical terms, the focal point is where the parallel rays of light will meet and this point will determine the distance of camera focus which is the focal length.  This distance is typically measured in mm or millimetres.  Depending on what is the preferred outcome of the photo, the focal length may be adjusted using different types of lenses.

When compared to normal human vision, normal focal length is said to be at 50mm.  This simply means that digital cameras that are equipped with lenses that have 50mm focal length can basically capture pictures or views that are similar to the naked eye.  When a person needs to have an image captured up close, the focal length must be adjusted to a lower value.  This is simply due to the fact that the distance of the focal point or subject from the camera lens must literally be shorter in order to get a close-up or macro type of shot. When the desire is to capture wide angles, the appropriate focal length is also lower.  Focal lengths lower than 35mm for example can be used to capture landscapes and wide views.

For people who wish to capture images that are farther away, the focal length must also be adjusted to make it longer.  For this particular purpose, lenses to be used must be able to focus at higher focal lengths like 200 mm for example.  Lenses at these focal lengths are referred to as zoom or telephoto lenses.  At this focal length, subjects or focal lengths that are far away may be focused for great clarity and exposure.

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