zoomlens

A zoom lens is a camera lens with a variable focal length, allowing the photographer to change the magnification and angle of view without moving the camera. The range is described by the smallest and largest focal lengths, such as 24-70mm. On full-frame bodies, wide-angle zooms typically run roughly 16-35mm, standard zooms around 24-70mm, and telephoto zooms 70mm and above. This contrasts with prime lenses, which have a fixed focal length.

Optical design and features vary, but most zooms use multiple glass elements with coatings to reduce aberrations and flare. Many incorporate aspherical or low-dispersion elements to improve sharpness. Some employ internal focusing or internal zoom to keep the lens length constant during use. Aperture behavior also varies: many consumer zooms have a variable maximum aperture (for example f/3.5-5.6); professional models often maintain a constant maximum aperture such as f/2.8 or f/4. Image stabilization is common to compensate for camera shake, and autofocus is provided by motors inside the lens communicating with the camera body.

Types and use cases include standard zooms (e.g., 24-70mm), wide-angle zooms (e.g., 16-35mm), telephoto zooms (e.g., 70-200mm), and superzooms that cover a broad range (e.g., 18-300mm). Advantages include flexibility and rapid framing; drawbacks can be bulk, weight, higher cost, and occasional optical compromises compared with prime lenses. For video, some zooms are parfocal (maintain focus during zoom), though many stills-oriented zooms are not.

History and impact: Zoom lenses became practical in the mid-20th century and improved with advances in coatings and computer-aided design. They are now ubiquitous in photography and filmmaking, providing versatile framing options across varied shooting scenarios.