Prime lens

The term prime has come to mean the opposite of zoom—a fixed-focal-length, or unifocal lens.

These advantages stem from having fewer moving parts, optical elements optimized for one particular focal length, and a less complicated lens formula that creates fewer optical aberration issues.

Larger maximum aperture (smaller f-number) facilitates photography in lower light, and a shallower depth of field.

Lens manufacturers such as ARRI Media,[5] ISCO Precision Optics,[6] Schneider,[7] Carl Zeiss AG,[8] Canon[9] and others still make variable focal length cine and video lenses regularly catalogued as variable prime lenses.

A variable prime is sometimes distinguished from a "true zoom" in that the latter maintains focus as the focal length is varied.

A 29 mm prime lens accompanied by a diagram of its internal lens elements.
Prime lenses have large apertures, compared with zoom lenses. These 85 mm lenses have maximum apertures of f /1.8 (left) and f /1.2 (right).
The Canon EF 50 mm f/1.8 II .
Three 50 mm prime lenses from Minolta with different design parameters. The left lens with lens speed 3.5 is for macro photography , where lens speed is of less concern. The middle one has lens speed 1.7, such a type comes as standard with many SLRs. The right lens has lens speed 1.2 and thus enables shorter shutter speeds in the same light situation.
Not all prime lens are physically small; those with internal autofocus stepping motors , such as this 85mm f /1.4 prime lens, are larger in overall size compared to motorless counterparts.