Prime lens

Started 1 month ago | Questions thread
A Marcus Forum Member • Posts: 50
Re: Prime lens

A prime lens is one that has a fixed focal length. Camera lenses act much like a projector lens in that they project an image of the outside world onto the surface of photographic film or a digital image sensor. The location of this projected image is called the image plane. The focal length is the distance lens-to-image plane when the camera is imaging a distant object. The focal length is a value that tells us if the angle of view will be wide-angle, normal, or a magnified telephoto view.

Historically most camera lenses were made to a specific unchangeable focal length. Serious photographers always carried a gadget bag chuck full of different focal length lenses. When we took pictures, we would reach in the gadget bag and select a lens that we felt best suited for the task at hand.

Don’t get me wrong, some early camera lenses were what we called convertible. We could unscrew some of the lens elements and replace them with others and thus make some adjustments as to focal length. It was the motion picture and TV industry that first experimented, in earnest. This began in the 1950’s. We are taking about camera lenses that you could zoom. Zooming means you could turn a knob or work a leaver or turn the lens barrel and change the view from wide-angle thru telephoto.

The zoom lens matured over time and for many applications, replaced the fixed focus lens. Now the fixed focus lens is optimized to image at just one magnification. As a result, these can be quite superior as to image quality. Thus in the jargon of photography, the fixed focus is often called a “prime”.

To answer your question, prime lenses are available in most every power (focal length). You could elect to forgo buying a zoom and return to an arsenal of primes in a gadget bag. I for one elect to use a modern zoom. However, I still keep a prime or two handy for special situations.

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