A 135mm lens is a type of telephoto lens commonly used in photography. It has a focal length of 135 millimeters, which allows it to capture subjects from a distance while maintaining a narrow field of view. This makes it ideal for portrait photography, as it can create a pleasing background blur, known as bokeh, while keeping the subject in sharp focus. These lenses are often favored for their ability to compress space and create a sense of intimacy in images. They are compatible with various camera systems, including DSLRs and mirrorless cameras, making them versatile tools for both amateur and professional photographers.