Prime Lens is a lens for DSLR cameras whose focal length is limited by the fixed design. Compared to a fixed focal length Prime Lens, a zoom lens is usually easier and cheaper to develop and produce. The lens inside our eye is actually a Prime Lens whose focal length within a limited range can be changed by the biological mechanism but it is never a zoom lens.
Terminologies associated with Prime Lens
Prime Lens is designed to be mounted on a Traditional SLR or newer DSLR cameras. A motor mechanism can exist within the Prime Lens (like USM), can be aspherical or L lens. Prime Lens usually produces a better resolution and better imaging performance and a higher light intensity. This makes Prime Lens ideal for staged or planned situations – like professional photography or Video Photography. This one of the reason is why the long shots and close shots of a movie are taken separately and edited later.
The other name used for a Prime Lens are – FFL or Fixed Focal Length Lens, Primary Focal Length Lens etc.
Technology behind and usage of Prime Lens
Probably the least costly and most popular Prime Lens is of Canon – a 50 mm Lens known as Nifty Fifty. Prime Lenses usually have a big aperture (that means a small f number) than a zoom lens of closer focal length. This property of Prime Lens creates a signature effect – shallower depth of field and bokeh, when taken in low ambient light.
Other points about Prime Lens
New users must be aware of the fact that, newer entry or mid level DSLRs mostly are not compatible with older Prime Lens of even the same manufacturer. The price of a Prime Lens is dependent on f number and the manufacturer. Carl Zeiss has brand specific Models of Prime Lens, even of same f number. These are important to look for while buying a second hand or used Prime Lens.