WHAT IS PRESSURE COMPRESSION AND HOW TO USE IT IN PHOTO
Have you ever heard someone say that a telephoto lens “compresses” the background or “smoothes” the image? We will understand what is meant.
The perceived distance between the subject and the rest of the scene depends on two things: the location of the photographer relative to his subject and the focal length of the lens. We will discuss this type of perspective distortion and how it can be used to create interesting photos.
What is not a compression perspective
Photographers say that pictures taken with a telephoto lens will have a shorter distance from the object to the background than pictures taken with a wide-angle lens. But this is not entirely true. If you take two photos from the same place, one with a wide-angle lens and the other with a telephoto lens, both pictures will have the same perceived distance from front to back — this is because the perspective has not changed. Now trim the image taken with the wide-angle lens to the same field of view as the telephoto shot. And yes, the quality will be terrible, but this is not the main thing. But it is necessary that the framing of both pictures looked identical.
Look at these two images. The first photo was taken with a focal length of 24 mm, and the second with a focal length of 70 mm. Both shots were taken from the same place, using a tripod, and the photographer focused on the bridge in the center of the frame.
Now we frame a wide frame so that the composition is the same as that of the photograph taken with a telephoto lens. In order to compare the pictures, it was necessary to increase the crop by about 285%, which is usually not recommended. Pay attention to the frame after cropping looked the same as a picture taken at 70 mm.
In the picture, the bridge is not distorted and the railing of the fishing pier on the right side of the frame is in the same place. In other words, when using a longer focal length, there was no distortion or “compression.”
The only difference is in the depth of field. In the photo taken at 70 mm, the foreground is not so sharp. A certain depth of field depends not only on the opening of the aperture, but also on the focal length, the distance from the camera to the object and the size of the sensor (matrix). But this is a topic for another article.
It is important to understand that in the example above, the distance from the camera to the object has not changed. As a result, the proportions in the image have not changed. If the photographer does not move, then the effect that the telephoto lens gives is exactly the same as cropping, but without loss of detail and sharpness.
Compression perspective occurs when you take a picture with a telephoto lens, but this is not due to the lens or its focal length. The reason is that we try to stay away from subjects when using a long-focus lens. This combination of a long-focus lens and the distance from the camera to the object gives the viewer the impression that distant objects are larger than they really are. As a result, the background seems to come close to the object.
The opposite effect occurs when using a wide-angle lens. When using a wide-angle lens, the photographer tries to stand much closer to the subjects compared to a telephoto lens. Because of this, close objects will look proportionally larger than distant objects. As a result, the background elements become much smaller and appear farther.
Below are two examples. The first shot used a long-focus lens. Note the illusion that the freighter is next to a flock of birds. In fact, between them there was a distance of about a kilometer.