What is a prime lens?
(Why the heck should I use prime lenses?)

Today's simple answer to the question of "what is a prime lens" is that a prime lens has only one focal length. In other words it doesn't have a zoom. It is a fixed focal length lens.

When I was first learning photography in the 1970s, the term prime lens meant a normal lens of about 50mm for a 35mm SLR camera. That focal length would give you a similar perspective that we get with our eyes.

The commonly used (but technically incorrect) answer to the question of what is a prime lens is what I will be discussing in this article.

Why would anyone use a prime lens? Zoom lenses are very popular and all point and shoot and most DSLRs come standard with zoom lenses.

You may have heard someone compare camera lenses and say that a prime lens is faster and sharper.

By "faster" we mean it has a larger aperture and is capable of shooting with less light needed for a proper exposure.

I love the results I get with my Canon 85mm f-1.8 prime lens, pictured above.

I like fast lenses because I shoot a lot of portraits and I like blurred, out of focus backgrounds.

Shooting wide-open with a large aperture gives you very narrow depth of field, so the background falls out of focus quickly.

The grass blades that were behind my model were not that far away, but were nicely blurred because I shot the photos at a wide aperture.

Prime lenses are also lighter than zoom lenses because of their simpler construction with not as many lens elements inside.

This means its easier to carry and easier to hold steady for a sharp photo. What about the cost of a prime lens?

In general, a prime lens can be more affordable than a zoom lens, because of its simpler construction. Prime lenses don't all necessarily come as super fast. You can buy Canon 50mm lenses with a maximum aperture of either f1.8, f1.4 or f1.2.

The corresponding differences in price are $125, $400 or $1600.

Yes you read the right. The fastest lens, the f 1.2 is very large and requires much more glass in its construction.

Perhaps another benefit not thought of when using a prime lens is that it forces you to physically move to change the composition of your photo.

Photographers can get lazy by relying on their zoom lenses too much. Using a prime lens with only one focal length can be a good way to challenge yourself to get more creative.

The last characteristic of prime lenses is their superior sharpness. Again due to a simpler lens design than zoom lenses, sharpness is not sacrificed like it can be when compromises are made during the design and manufacturing processes of zoom lenses.

This has never been much of an issue for me. I've never had sharpness issues with my high quality zoom lenses.

There are certain distortions, such as pincushion and barrel that are present to varying degrees with zoom lenses that I find objectionable. Prime lenses have very little distortion.

So, if someone asks you "What is a prime lens for?," now you know all the answers.

Photography Definitions. For more explanation of other terms and photography definitions.

Happy Shooting
Photo TipMan

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