We all know what a zoom lens is. A prime lens is one that does not zoom. It has a fixed focal length. Both zoom and prime lenses offer huge advantages to your photography, so don't think you have to stay in one camp or the other.

But in comparing zooms to primes, you'll find that prime lenses are smaller, lighter, faster, sharper, and cheaper than zoom lenses. Is it obvious where my preference lies?

Size

Most primes, especially in the normal range of 20mm through 60mm, are very compact and light. They protrude maybe two inches from the camera body, rather than the several inches in length of most zooms. Primes are also noticeably lighter than zooms. You will have to carry one or two extra lenses in your bag to recreate the versatility of a zoom, but if you know what you need for any given shoot you might still end up with a lighter load. The photo above shows a Canon 24-70mm zoom lens next to its tiny brother, the 50mm.

Speed

The speed of a lens indicates the amount of light it lets in through its maximum aperture. A fast zoom lens has a maximum aperture of f2.8. A normal prime has an aperture of f2.0, which lets in twice as much light as the f2.8 zoom. And primes are often available with ultra-fast f stops like f1.4 and even f1.2 and f1.0 for extreme low-light/shallow depth of field photography. Zoom lenses with such fast apertures simply don't exist.

Sharpness

While a zoom is designed to accommodate various focal lengths through slight compromises in quality, a prime lens is designed for one specific length and optimized for that length alone. To be fair, some zooms are so good that the difference in quality is so slight that you can't really see it. Still, primes still win in virtually every category other than convenience.

Cost

Primes of all lengths are almost always less expensive than zooms. You may have to buy two or three primes to cover the range of one zoom, but the benefits may be enough to convince you.

Where Primes Win

I've listed a lot of quality and convenience reasons why I think prime lenses are so wonderful when compared to zooms. But there's another reason, and it comes into play when you're learning photography. It's how you learn to see through each lens. When I started in photography, I didn't have the money to buy an entire bag of lenses right at the start. I had to scrape together the money to buy each new lens. So every few months I'd buy a new prime lens. The great part of what seemed like depravation was that I had the time to learn what each lens did. I learned to choose lenses for a the look they brought to my work. Sometimes we use zooms just for their convenience, and we forget that the focal length we're shooting at makes a difference in our photos.

Where Zooms Win

One zoom lens on your camera can do the job of several prime lenses. And with a zoom, you rarely waste time changing lenses. Photography is unpredictable and there will be times when you're just reacting to what's in front of you. Using a zoom lens allows you to stay focused on what you're shooting and not worry about having to change a lens as the situation changes. If your subject moves in close or puts their arms up in a victorious cheer, you can simply zoom out and re-compose on the fly.  Especially when photographing moving subjects, action, and candids, a zoom lens can be essential.