Through the Looking Glass
You look through the viewfinder of your camera and see a magic world. The world you see is determined by how you look at it.
Depending on your selected focal length, the angle of view you see through the view finder may or may not resemble what you see with your naked eyes. Human vision is said to match a focal length of somewhere around 50mm but this can't be more than an approximation. Your visual field is a rendition stitched together from what each of your eyes sees. You likely have at least a vague sense that your vision is wider from side to side than it is in height, but there really aren't any clearly defined edges in any direction. If you look to the side to find how far your field of vision goes, that field moves with your eye movement. If you keep your eyes fixed, all you can really say is that the further off-axis you consider, the less sure you are just what you see, if anything. You can't probe for the edge of your vision without altering the direction you are looking. A camera lens sees a much more clearly defined slice of what is in front of it. Given the geometry of a lens, the image projected starts as a circle, but is typically cropped to a rectangle based on the shape of the sensor recording the image.
Lens focal lengths can vary, from extremely wide to extreme telephoto. So, are focal lengths outside of the "normal" 50mm range somehow not normal? In this context "normal" merely means "approximating human vision," but other focal lengths aren't really "abnormal" in any way, they're just different. Everything works exactly the same way, but the angle isn't what we're used to. People often say that wide angle lenses have a distorted perspective, but that isn't really so. It's just that we aren't used to seeing so much at one time, and that to make things look as big as we're used to, we have to get closer to them than normal. And it's this change of distance that creates an appearance of exaggerated perspective, not the focal length change in and of itself. It has been well established that a picture shot with a telephoto will look the same as one shot with a wide angle from the same spot and then cropped such that the two images have the same framing. "Normal" isn't a property of a lens's focal length. It's just a description of what we're used to.
But we don't think of our vision or that of a midrange 50mm lens as being at all strange. An extreme wide-angle lens seems to distort perspective when it really doesn't. And a standard 50mm lens seems "normal" when it's doing exactly the same thing as any other lens. All lenses present the world based on their focal length. Some take in wider fields of view, some narrower. But their all pretty much the same. Exposure, depth of field, and other photographic variables are equally hard to compare to human vision. The concepts are the same between the two, but they aren't exactly comparable. Look through a lens or don't. Either way, the world you see is influenced by the properties of the visual system involved.
Indeed, one of the most valuable things about the variety of camera lenses and focal lengths available is that they allow us to see things in a new way. When Alice went through the looking glass, she entered a new world filled with new sights. When you look through a camera, you too can see the world in a new way. By varying the focal length and other settings, a photographer can accentuate certain aspects while diminishing the relative importance of other aspects in an image.
I find that I take predominantly wide angle and some telephoto shots, but very few shots in the "normal" 50mm focal length region. Perhaps that's just me, but it seems to be true to some degree for many landscape photographers. Wide angles are certainly called for to encompass some vistas. But it strikes me as curious that so many landscape images get shot at focal lengths other than what purportedly passes for that of human vision. If the objective were to represent things as the average person would actually see it if they were there with you, then the standard landscape lens should be the 50mm, but such is not the case. Clearly, the objective involves more than just literal accuracy of representation. Again, speaking for myself, I want to convey not only what it looked like, but also what it felt like to be there in front of that expansive vista.
I want to convey as much as I can through my looking glass.