The ‘Nifty Fifty’. The focal length of a lens is the distance between the optical centre of the lens and the point of focus. Wide angle lenses have a short focal length, e.g. 16mm, and make distant objects appear further away, as well as widening the gap between objects at different differences. They can provide a sense of space and tranquility, and are therefore often used for landscapes.
Telephoto lenses, e.g. 300mm, bring distance objects closer, and squeeze together objects at different distances. They are useful for making a shot appear crowded or ‘busy’, as well of course for when you can’t get close enough to your subject to shoot it otherwise.
50mm lenses are special and have special qualities, as 50mm is approximately the focal length of the human eye. As such they are neither telephoto nor wide angle, and are often called ‘standard’ lenses.
Photographs taken at 50mm connect more directly with the viewer, as the image looks as he or she would expect to see it, not compressed or expanded as is the case with telephoto or wide angle lenses respectively. 50mm shots have a sense of naturalism and immediacy, which can be exploited by the photographer to create engaging or pleasing images.