A telephoto lens is a specific type of long-focus lens used in photography and cinematography. It allows photographers to utilize a focal length that is shorter than the lens physical length. Telephoto lenses are sometimes broken down into sub-types of short telephoto (85–135 mm in 35 mm film format), medium telephoto (135–300 mm in 35 mm film format), and super telephoto (over 300 mm in 35 mm film format) .

Telephoto lenses make far-away objects appear closer to the camera, but they can also be used creatively to capture unique shots. They are often used in wildlife photography to capture images of animals from a distance. Telephoto lenses have a focal length longer than the diagonal size of the image it takes, and they need many pieces of glass inside to bring subjects up close to the camera. This often makes them large, heavy, and expensive.

Telephoto lenses can be zoom lenses, such as 70-300mm, or prime lenses, such as 200mm. They are also used in telephoto mode on some mobile devices, allowing users to zoom in on a scene or a single subject. The telephoto look refers to a visual effect created by telephoto lenses, where whatever is in the background seems to be visually closer.

In summary, a telephoto lens is a type of long-focus lens used in photography and cinematography that allows photographers to capture far-away objects up close. They are often used in wildlife photography and can be expensive due to the many pieces of glass inside. Telephoto lenses can be zoom lenses or prime lenses, and they are also used in telephoto mode on some mobile devices.