What Is Perspective?
Both literally and figuratively, perspective is point of view.
Figuratively, as in “What is your point of view on Russia’s annexation of Crimea?”
Literally, as in “Where did you stand when you took that photograph?”
In a photograph, we interpret perspective by looking at the size relationships between objects.
The principle is simple: distance between camera and object (known as object distance) controls image size. The closer the camera, the bigger the image: image size is directly proportional to object distance.
Let’s say you have two people, Jane and John, standing in front of your camera. Jane is six feet from the camera, and John is 12 feet from the camera. In this photograph, John is going to be half the size of Jane, because he is twice as far from the camera.
Our Brain Has Two Choices
Presented with this two-dimensional image, our brain has two choices. Either John really is half Jane’s size, or John is standing farther from the camera than Jane.
Most of the time, our brain makes the right choice, except when it is fooled by an optical illusion—such as someone appearing to hold the Washington Monument in the palm of their hand.
When we see big Jane and small John, we say the space between foreground and background is expanded, and the photograph has a sense of depth—even though we know a photograph is two dimensional.
For our next photograph, let’s simply move the camera back so it is 60 feet from Jane. We’ll keep the distance between Jane and John the same as it was for the first photograph—six feet.
Move the Camera, Change the Perspective
What will the second photograph look like? We know image size is directly proportional to object distance. Jane is 60 feet from the camera, whereas John is 66 feet from the camera. Therefore, John is going to appear 10 percent smaller than Jane—because he is 10 percent farther from the camera.
How will our brain interpret this slight reduction in size between Jane and John? In this case, we will perceive Jane and John being relatively close together. The space between them will appear to have been compressed in comparison to the first photograph, and the image will appear flattened.
Notice that this compression effect was caused simply by moving the camera—by changing perspective. Nothing else in the scene changed. Notice too that we haven’t even mentioned lens focal length yet.
The So-Called Telephoto Effect
Photographers and photographic books often attribute the expansion or compression effect to lens choice: a wide-angle lens expands space, whereas a telephoto compresses space. In other words, lens focal length affects perspective. This is a fallacy.
As we have just learned, perspective is controlled solely by where you place the camera. So how did this fallacy come to be?
Simply put, when photographers are very close to their subjects, they tend to use a wide-angle lens, to take in a larger field of view. And when they are very far from their subject, they tend to use telephoto lenses, to magnify the image—image size is directly proportional to focal length.
Correlation, Not Causation
This correlation of lens focal length, distance from subject, and expansion or compression of space has led photographers to assume that it is the lens choice that is determining the perspective, when in reality it is camera placement.
You can easily prove this to yourself by making two photographs of the same scene from the same vantage point—the first using a telephoto lens, and the second using a lens with a much shorter focal length.
Crop and enlarge the second photograph so it matches the first, and you’ll see no difference between the two in terms of perspective. The compression of space, i.e., the “telephoto effect,” will be present in both images—even though one was taken with a non-telephoto lens.
Of course, when you enlarge a photograph, you risk losing image quality. So I’m not saying get rid of your telephoto lenses! They are great for getting high-quality images of far away subjects. But they don’t magically compress space—it’s the distance between camera and subjects that does that.
The photographs below were all taken from the same spot. I used three settings on my zoom lens: 80mm, 230mm, and 400mm. (Because my Nikon D70s has a 1.5x-crop sensor, these focal lengths have a 35mm equivalent of 120mm, 345mm, and 600mm.)
I used the photograph taken at 80mm and cropped it in Photoshop to match as closely as possible the photographs taken at 230mm and 400mm.
As you can see, the “telephoto effect,” or compression of space, is apparent in the cropped photographs, demonstrating that this effect is not caused by lens focal length but by camera position.