fixedfocallength

Fixed focal length, commonly referred to as a prime lens, is a camera lens with a single, non-variable focal length. Unlike zoom lenses, which provide a range of focal lengths, fixed focal length lenses offer a fixed angle of view for a given sensor size. To change composition, the photographer must move the camera closer or farther from the subject, rather than rotating a zoom ring. The term fixedfocallength is often used interchangeably with prime lens in photography and cinematography.

Advantages of fixed focal length lenses include a wider maximum aperture, which allows brighter images and shallower depth of field. They are often noted for high optical sharpness and lower distortion, and they tend to be more compact, lighter, and sometimes more affordable per unit of image quality than zooms. With fewer moving parts, primes can also be more robust and reliable in certain conditions.

Limitations include a lack of zoom versatility, requiring the photographer to physically change lens or spacing to frame a scene. This can be less convenient for dynamic shooting situations. On some camera bodies, especially smaller ones, using a prime lens may result in a narrower effective field of view, requiring additional lenses to cover wide and telephoto needs.

Common focal lengths used in fixed focal length lenses span wide to short telephoto, for example 24–28mm, 35mm, 50mm, and 85mm. These are favored for street and documentary work (35mm, 50mm), portraits (85mm), or landscapes (24mm). Prime lenses are valued for their optical characteristics, compact form, and low-light performance.