Photography terms: Focal length

This term is not so known to those who use non SLR cameras, because to be understandable for non SLR cameras is used term zoom and marked with a number. That number (for example 5x) shows how many times can the angle of view be shortened in the maximal zoom than in the minimal. And the angle of view is determined by a the focal length which actually shows the distance between the first optical surface of the lens and the image sensor or a film in earlier times. Real focal length is marked in millimeters and since the fixed focal length lenses are rare, most common are zoom lenses. For example 28-135 mm lenses have almost 5x zoom (135/28). Wide angle lenses have a focal length until 50 mm, from 50 to 65 are standard lenses, from 70 to 135 are telephoto lenses and those above 135 mm are super-telephoto lenses. Wide angle lenses make deformations to the objects on a picture, those ultra wide lenses are called Fish eye lenses and their angle of view can be up to 180 degrees. That is possible with focal length of 7.5 mm, so because of that for making portraits (photographing people) is recommended to use telephoto lenses so the person on the picture would actually look like the photographed person. For you who don’t have an SLR camera and are unable to see the real focal length, when photographing portraits we recommend to use at least 3x zoom. Take the camera, and try to see the difference.