When it comes to telephoto lenses, most people think the main use is to take photos in situations where you can't get close to the subject, things like being stuck at the back of the chapel during a wedding ceremony. And while this reason is valid, there are more uses than just that.
When using a zoom lens, it's easy to get tied up in the fact that you can make your subject appear larger in the frame from farther away. And while this is useful in situations where you simply can't get closer to your subject, I find myself reaching for my zoom lens for many different reasons.
Reason One: Making The Background Appear Larger and Closer
When you are taking images inside a chapel with a zoom lens, it’s really hard to see this element of zoom lenses come into play. That's because usually, the background is pretty close to the subject. But using a zoom lens outside is when you will really see this element come into play. If I take a photo of a subject with my Tamron 70-180mm f/2.8 G2 lens at 70mm, below is what that result might look like.
Now, using my zoom lens, if I get farther away from my subject and make them around the same size in the frame, but now at 180mm, below is the result I get.
What’s happening here is known as compression. And while most people think this is a quality of the optics in a zoom lens, it is actually just a result of being able to get farther away from the subject. You see, at 70mm, the subject is maybe 10 feet away from me and the background element is at 20 feet away. But if I double the distance between me and the subject, I’ve only added a smaller fraction of the distance between me and the background element. So the subject gets smaller at a quicker pace than the background element. The distance ratio between camera, subject, and background is what causes the compression. From here, the zoom lens simply allows us to take the image from farther away. Below are some more examples of using this technique to make background elements appear closer to the subject. Below are some more examples where I used compression.
Reason Two: More Bokeh!
Another great use for a telephoto zoom lens is to create amazing background bokeh, which is something most people associate with larger apertures, like f/1.4. And yes, a large aperture will give you a more shallow depth of field, but the amount of bokeh in an image is also related to the distance between the subject and the background. For example, if you take an image at 35mm f/1.4 of a subject standing in front of a wall, the wall won't be that nice out-of-focus blur because it’s so close to the subject.
Now, step the subject farther away from the wall, and the wall will become more out of focus.
Keep going, and the wall will get way out of focus, but eventually, the wall will become smaller and smaller in the frame to the point that it's no longer a usable background.
But, similar to the idea of compression, we can use a zoom lens to get our subject even further from a background element while still making that background element appear larger in the frame. Because of this fact, we can have background elements fill the frame while being even farther away from the subject, causing it to blur to that nice creamy bokeh.
But one thing to keep in mind is that some lenses have what’s called a variable aperture. This means as you zoom in, the widest available aperture actually gets smaller. So, you could be starting at f/2.8 and then end up at f/4 as you zoom in, which sort of defeats some of the purpose of this technique. This is why I prefer lenses like my Tamron 70-180 f/2.8 G2 because the aperture remains a constant f/2.8 no matter what focal length I choose. Below are some more examples where I used a telephoto lens to create more bokeh.
Conclusion
Though using a zoom lens in order to take photos of faraway subjects is absolutely a good reason, don’t get stuck on just that single use. By using something like the Tamron 70-180mm f/2.8 G2, you can also use compression to your advantage in order to make background elements appear larger in the frame relative to your subject. You can also use these same principles to get images with a more out-of-focus, bokeh-filled background.
