Have you ever heard someone say that a telephoto lens “compresses” the background or “flattens” an image? What exactly does this mean? The perceived distance between your subject and the rest of the scene is dependent on two things: where you stand relative to your subject to take the photo and the focal length of the lens you choose. In this short article, I want to discuss this type of perspective distortion, and how to use it to compose exciting photographs.
What Lens Compression Isn’t!
I have often heard photographers say that images taken with a telephoto lens will appear to have a shorter subject-to-background distance than those taken with a wide angle lens. This isn’t completely true. If you take two photos from exactly the same place, one with a wide angle lens and one with a telephoto lens, they will have the same perceived distance from front to back – that’s because the perspective has not changed! To see this, crop an image taken with a wide lens down to the same field of view as a telephoto lens. And yes, the quality of the crop will be horrible, but that’s not the point! The point is that the crop will look identical to the telephoto shot.
Take a look at these two images. The first was taken at a focal length of 24 mm, while the second was taken at a focal length of 70 mm. Both shots were taken from exactly the same place, on a tripod, and I focused on the bridge at the center of the images.
NIKON D800 + 24-70mm f/2.8 @ 24mm, ISO 100, 1/500, f/8.0
NIKON D800 + 24-70mm f/2.8 @ 70mm, ISO 100, 1/320, f/8.0
Now I am going to crop the wide shot so that the composition is the same as the telephoto shot. To compare the shots, I had to enlarge the crop approximately 285%, not something I would normally recommend doing! Notice how this crop looks the same as the shot taken at 70 mm. The bridge has not become distorted and the railing of the fishing pier (on the right side) is in the same location. In other words, there was no distortion or “compression” using the longer focal length.
NIKON D800 + 24-70mm f/2.8 @ 24mm, ISO 100, 1/500, f/8.0
The only difference is their depth of field. The foreground is not as sharp in the photo taken at 70 mm. It turns out that depth of field is a property, not only of aperture, but also of focal length, camera to subject distance and sensor size. However, that’s a discussion for another article!
The important thing to realize in the above example is that the distance from the camera to the subject did not change. As a result, the proportions in the image did not change. If your feet don’t move when you take a shot, then the effect that a telephoto lens gives is exactly the same as cropping, although without the loss of detail and sharpness that you would find in a crop.
What is Lens Compression?
So what is lens compression then? Lens compression does occur when you take a picture with a telephoto lens, but it is not because of the lens or its focal length. It is because we tend to stand farther away from our subjects when we use a long lens. This combination of long lens and camera-to-subject distance gives the viewer the impression that distant objects are larger than they actually are. As a result, it gives the appearance that the background has pulled in closer to the subject. The opposite effect occurs when you use a wide angle lens. When we use a wide lens, we tend to stand much closer to our subjects compared to a telephoto lens. Because of this relative closeness, near objects will look proportionally larger than objects in the distance. As a result, the background elements become much smaller and seem farther away.
Here are two examples. In this first shot I was using a long lens. Notice how close the freighter seems to the birds. In actual fact, they were probably about a kilometre away from each other.
NIKON D7100 + 200-400mm f/4 @ 380mm, ISO 800, 1/1250, f/5.6
In this photo of a goat I used a very wide angle lens. Notice how large the goat’s head appears relative to his body.
NIKON D7000 + 10.5mm f/2.8, ISO 400, 1/640, f/8.0
The important thing here is not that I used different lenses, but the fact that my subject to camera distance was drastically different in each picture. For the picture of the birds and freighter my camera-to-subject (birds) distance was probably 100 metres. In the goat picture, my camera was literally inches away from his nose!
These last two examples don’t exactly explain lens compression though, especially since they are of two different subjects. To clarify why compression happens, lets look at a series of photographs. These images were taken so that the subject (my very cooperative and patient daughter) appears relatively the same size in each photo. To do this, I had to move the camera farther away from her each time I increased the focal length. This is worth repeating. I had to adjust the distance between her and the camera to keep her the same size in the frame. Pay close attention to the background. Also, just a quick note, I am not a portrait photographer, so no harsh comments about the lighting and posing please!
The first image is taken at 24mm. Look at the wide expanse of background; it gives the viewer a sense of place. Notice the flag and how far away the flower planters appear. Also, because I was standing so close to my daughter, her nose is unfortunately looking rather large!
NIKON D800 + 24-70mm f/2.8 @ 24mm, ISO 100, 1/500, f/5.6
This next shot was taken at a focal length of 70mm. The flag appears larger. Also notice what is happening to the trees in the background. They seem closer, as do the planters.
NIKON D800 + 24-70mm f/2.8 @ 70mm, ISO 100, 1/400, f/5.6
105mm. You can no longer see the flag. The cherry blossom trees are becoming more prominent.
NIKON D800 + 80-400mm f/4.0 @ 105mm, ISO 100, 1/400, f/5.6
My focal length is now 200mm. The background is getting even closer still. It is very hard to get a feel for distances now.
NIKON D800 + 80-400mm f/4.0 @ 200mm, ISO 100, 1/320, f/5.6
This final image is taken at 300mm. The planters were about 10m apart in reality, but look how close together they appear now.
NIKON D800 + 80-400mm f/4.0 @ 300mm, ISO 100, 1/320, f/5.6
Compression is actually due to the distance between the camera and the subject. With longer focal lengths (which have a narrow field of view), you have to step back to keep your subject the same size in the frame. A wide angle lens has a much wider field of view. To keep your subject the same size in a wide angle image, you need to get very close to your subject. In the shots above, the distance from my daughter to the background didn’t change; it was the distance from the camera to her that was changing as I changed focal lengths.
Think of it this way. If an object is close to you, it appears relatively large. Double the distance between you and the object and its size is halved. Increase that distance by ten times, and the object is one-tenth the size. In the wide angle cases, the distance between the camera and my daughter is short compared to the distance between my daughter and the background. Thus, Lisa is relatively large compared to the trees (as objects appear smaller with distance).
In the telephoto cases, Lisa and the background appear closer in size because they are both relatively far away from the camera. The distance between her and the background is becoming less significant as I increase the distance between her and my camera.
Lens Compression and Composition
You can use lens compression to your advantage once you understand that it is the distance between the camera and your subject that causes this distortion. For example, if you are trying to take a portrait, and there are a lot of distracting elements in the background, try using a long lens and standing back from your subject. By stepping back, you can isolate your subject against a single element in the background instead of all the clutter.
NIKON D800 + 80-400mm f/4.0-5.6 @ 200mm, ISO 400, 1/500, f/7.1
By using a longer lens, not only could I stay a safe distance from the horse and rider, but I was able to isolate them from a very busy background
NIKON D7000 + 200-400mm f/4.0 @ 2100mm, ISO 400, 1/800, f/4
I set up so that when the hummingbird hovered after drinking from the feeder, he was in front of a pink and green bush in the background
If you are trying to show the vastness of a landscape, get close to a foreground element with a wide angle lens. This will give the impression that the distant features are even grander.
NIKON D90 + 18-200mm f/3.5-5.6 @ 18mm, ISO 400, 1/90, f/9.5
NIKON D7000 + 14-24mm f/2.8 @ 14mm, ISO 800, 1/320, f/11.0
Conclusion
So to summarize, the closer your camera is to the subject, the farther away the background will appear. This will exaggerate the relative subject and background sizes and distance. As you move your camera farther away from the subject, the foreground and background will appear closer together. Use this to create intimacy between your subject and a distant background.
When you are composing your photos, think about your camera-to-subject distance. Instead of just zooming your lens in and out, try moving your feet! Get close to your subject with a wide lens or farther away with a telephoto. Experiment with this technique and see how the dynamics of your photographs are impacted! Have fun shooting!
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from Photography Life https://photographylife.com/what-is-lens-compression
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