Angle of View

Why do lenses come in so many different sizes? It's not just so lens manufacturers will have more product to sell. It's because they are all tools in the cinematographer's toolbox. Just like a mechanic uses a wrench in some circumstances and a ratchet in others, a cinematographer will use the tool that best suits the needs of a given shot. Different lenses are used to tell a story based on their angle of view. 35mm lenses, such as those used in professional filmmaking, typically are a fixed focal length (such as 18mm or 100mm) are known as prime lenses. Lenses in digital video or HD cameras are variable in length (largely because it’s the best balance of cost and flexibility) are known as, well, zoom lenses!

The focal length of the lens directly affects the angle of view. The longer the focal length of a lens, the narrower the angle of view and the more it magnifies the image: The shorter the focal length, the wider the angle. Let's look at the examples below to see how this works.