When you’re starting out, you’ll hear the term “focal length” get thrown around a lot. So what is it? Are people just talking about the number on the lens that you zoom to? In this lesson, I’m going to go over focal length, and how you can really change your photos by zooming in/out to a different focal length.

Part 1: Zoom

To start out, focal length is the distance between the point of convergence in your lens to the sensor. To see this, check out the Expert Photography website for a more in depth explanation as well as a diagram. When you first start out, you’re most likely going to have your normal 18mm to 55mm lens. The numbers represent the focal length. Simply turning the lens from 18mm to 55mm will zoom in to where ever you have your camera pointed. Below, I’ll show you a photo taken at 18mm.

In this shot, the car looks fairly small (and clean which will change in the next few photos). Since this was taken at 18mm, you’re at a wider field of view so you can see the road leading up to the car, a lot of the background, and you have a decent amount of sky. Let’s zoom in a little bit and see what this does.

Now I’m zoomed in to 55mm. I haven’t changed the position my camera is at all. As you can see, the car takes up a lot more of the photo. You can see less of the road, background, and sky in this shot.

Above, I’ve jumped to 210mm. You are unable to see anything other than the car and a little bit of the road. Again, I haven’t changed the position of my camera at all. I’m only zooming in. This is a very brief overview on using different focal lengths to zoom into what you’re shooting. It’s a way to get closer to your subject without getting closer.

Part 2: Perspective

You might have noticed I made a point to let you know that I hadn’t changed the position of my camera in the photos taken above. Why? Focal length can be used in two different ways. Below, I’m going to go over a few more shots taken at different focal lengths. I tried to position the car exactly the same to show how the background changes.

Above you can see a photo taken at 210mm and my car filling the frame. For those who don’t understand the phrase filling the frame I just mean that the car is going from one edge to the other edge of the photo. You can also see the background is compressed which will make a little more sense when you see the following photos. Essentially, compressing the background means everything behind the subject will be a lot closer. It can be a great way to separate the subject from the background if you’re using a large aperture like f/2.8 which I talked about in Lesson 2.

This shot was taken at 99mm. It was a failed attempt at 100mm, BUT it’ll still work fine for explanation purposes! You can see that the car is taking up roughly the same amount of space in the photo, but the key difference is what you see everywhere else. There’s not a lot of detail in the road, but you’ll notice in this photo you can actually see the sky. The difference between 210mm and ~100mm is not much, but it is noticeable.

Now I’m shooting at 55mm. Compared to the first photo at 210mm, you can see a drastic change between the two. You’re able to see a lot more of the sky whereas you couldn’t see anything before. There are also some changes in the car. Below I’ll post side by sides comparing 210mm to the wider angle shots. Pay attention to the front of the car.

210mm 35mm

The photo on the left is 210mm and the one on the right is 35mm. Changing the focal length by 175mm makes the photo look completely different! On the left, you can see both headlights (albeit not fully), you can see the fence, and the car looks a little taller in the photo on the right taken 35mm.

210mm 18mm

Remember how I said the 210mm and the 35mm photos look completely different? Shooting at 18mm or wider angles can really distort what you are taking a photo of. I tried to fill the frame the same way in both photos and they look nothing alike. You’re able to see a lot of the treeline, but the car doesn’t look right. This is just a photo of a car, but this distortion can happen if you’re photographing people, or anything else.

To conclude this lesson, remember that “zooming” your lens has more than one use. You can get closer to your subject, or you can use your focal length to completely change the look of the photo and subject. Next time you’re out shooting, even if you’re using your 18mm-55mm kit lens, try taking a photo at 18mm and the “same” photo at 55mm and see for yourself!