Ever notice how buildings don’t appear to be falling over when you look at them? They should. Look at a picture of a building taken from ground level, an image that shows the whole building from first to last floor. You’ll probably see a building that is leaning, appearing in danger of laying down on the street below.
But that isn’t what we see, is it? Our brains have this marvelous ability to correct for perspective. We “know” the building goes straight up from the ground so our brain interprets the image from the eyes to show us that. Keeps us from dodging apparently falling buildings during a downtown stroll.
Philosophically it’s an interesting discussion about the nature of reality. Buildings do actually go straight up in the air (normal ones, that is) to minimize the effect of gravity. So that is reality. But our eyes, behaving as a camera does, really captures an image of tilting perspectives. To our mechanical eye-system leaning buildings are a reality. Then our brain, armed with learning and knowledge, corrects the image before it reaches our consciousness, adjusting the eye’s version of reality into the real version of reality.
And people complain about photographers manipulating their images….
Speaking of which, there are a couple of ways to deal with leaning buildings in photographs (assuming you want them to look “normal”). The first is to buy a view camera, or any camera where you can adjust the plane of the film/sensor separate from the plane of the lens. It’s not something you usually worry about because the vast majority of cameras the typical person uses has these two planes fixed and parallel to each other. And if all you do is shoot straight ahead with your camera parallel to the ground that’s not a problem but you’ll find all your buildings will have their tops chopped off. They’ll be straight but headless.
A view camera enables you to keep the film/sensor plane (essentially the back of the camera) parallel to the object you want to be straight, while allowing you to move the lens plane upward until you get the whole building to show upon the film/sensor. Very cool trick, but there’s that view camera thing to deal with. Not very user friendly in our digital, snap-and-go society.
Fortunately there’s a software solution that will work much of the time. Photoshop has a Lens Correction tool that enables you to mimic the action of a view camera – sort of. You can adjust your image as if you’re tilting the lens plane up or down, or side to side. For example, here’s an image I “corrected” using this tool.
It’s not a perfect adjustment nor an actual mimic of a view camera. For example, in the corrected version the tall building has gotten “fatter” a bit. With a true view camera the building would retain the same proportions, it would just lean forward and straighten up. At least this way the image mostly matches what our brain is telling us reality ought to look like!