Before introducing camera lenses, we should know what is “focal length”? The most fundamental characteristic of a camera lens is its focal length, which is typically expressed in millimeters (mm). It is not a measurement of the length of a lens. Instead, it is a calculation of the optical distance from the point where light rays converge to form a sharp image of an object to the digital sensor or 35mm film at the focal plane in the camera. When a lens is focused to infinity, the focal length of the lens can be measured accurately.

The focal length of the lens gives information about the angle of view, or how much how much of the scene will be caught. When the focal length is longer, the angle of view is smaller and the magnification is greater. When the focal length is shorter, the angle of view is wider and the magnification is lower.

Now, we can understand better main types of camera lenses. The focal length of a lens is its most distinguishing characteristic; the bigger the number, the longer the lens. Use a longer lens with a long focal length when your subject is far away and you want to pull it in closer in the frame. This will allow you to get a better sense of scale. When you use a lens with a long focal length, you are able to focus in on a specific location in the landscape. On the other hand, when you use a lens with a shorter focal length, you are able to capture a greater portion of the globe and present a more panoramic picture. We can classify lenses into the following categories: prime, zoom, telephoto, wide angle, fish eye, and macro lenses.