A 450mm telephoto lens is a lens with a long focal length that allows you to capture distant subjects. The specifications of a 450mm telephoto lens may vary depending on the type, brand, and mount of the lens. Some common specifications are:

• Focal length: This is the distance between the lens and the image sensor when the subject is in focus. A 450mm telephoto lens has a focal length of 450mm, or equivalent to 450mm on a full-frame camera. Some telephoto lenses have a variable focal length, such as a zoom lens that can change from 150mm to 450mm.
• Aperture: This is the opening in the lens that controls how much light passes through to the image sensor. A 450mm telephoto lens may have a fixed or variable aperture, such as f/4.5 or f/4.5-5.6. The lower the f-number, the larger the aperture and the more light it can gather. A larger aperture also creates a shallower depth of field, which blurs the background and isolates the subject.
• Image stabilization: This is a feature that reduces camera shake and blur when shooting handheld or in low-light conditions. A 450mm telephoto lens may have an optical or digital image stabilization system, such as DC or OIS. Some lenses rely on the camera body to provide image stabilization, such as Pentax lenses that use SR (Shake Reduction).
• Autofocus: This is a feature that automatically adjusts the focus of the lens to achieve sharp images of the subject. A 450mm telephoto lens may have an internal or external autofocus system, such as USM or HSM. Some lenses have a manual focus override or a focus limiter switch to fine-tune the focus or speed up the autofocus performance.