What is focal length?

It happens to most dSLR owners. You get the camera, and you’re thrilled with it, but you’re also awed and a wee bit afraid because the whole thing is just so confusing. It doesn’t take very long before someone tells you that the kit lens, the lens that usually comes with the camera, is a piece of garbage. This sends you off to the web to find a better lens, but there are all sorts of complicated and cryptic numbers and letters and symbols and the like. The whole thing is so bewildering that you just want to go to the drugstore and buy a disposable film camera.

Don’t fear! The cryptic numbers and letters that are used to describe lenses are really (mostly) pretty straightforward. If you’ve been reading this blog, you’ll probably find that you’re already familiar with most of the terms, so this won’t be too hard.

Before we start looking at lenses, there’s on term that I may not have explained yet– focal length. In a nutshell focal length is how long the lens is. It’s a little bit more complicated than that, of course, and the technical definition isn’t all that interesting, but there is really only one thing you need to know, and it’s really easy. The longer your lens is, the more the image is magnified.

Let’s say that you’re taking a picture of the tree in your yard, and there’s a bird perched on a branch. If you use a short lens, you’ll get the whole tree into the picture, and the bird will be a tiny little blob. If you use a long lens, you’ll just get the bird and the branch that he’s sitting on, and you’ll be able to tell that he’s a blue jay. If you have a really long lens, you’ll be able to see the worm in his mouth. Cool!

If you have a zoom lens, and you probably do, you’re probably already familiar with this concept. Zoom in and everything gets closer. Zoom out and you get more of the area in the picture.

Polar Bear by Joe DeckerLong lenses are called telephoto lenses. The prefix tele- means distant, so telephoto lenses let you take pictures of distant things. This amazing shot of a polar bear, taken by award-winning nature photographer Joe Decker, was taken with a telephoto lens. Joe’s a smart guy, and he knows if he gets too close to a bear he runs the risk of being dinner.

Bryce Canyon Sunrise by Joe DeckerShort lenses are called wide-angle lenses, because they let you get a really wide view of your surroundings. Again, I’ll use one of Joe’s photos, this one a sweeping view of sunrise in Bryce Canyon. I honestly don’t know what lens was used for this shot, but the only way to get such a grand vista is to use a wide-angle lens.

Here’s what you should remember about focal length: using a wide-angle lens is like stepping back from the picture so that you can see more of the action, while using a telephoto lens is like walking over to the subject so you can get a closer look. That’s really all you need to know for now.

Once again, I’d like to thank Joe Decker for giving me permission to use his images as examples. I highly recommend checking out his work, especially some of his recent images from Iceland and Greenland.

In the next lesson, I’ll take a closer look at a couple of lenses and explain what all of the numbers mean.


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