It has been said that what you see depends on where you stand. This is quite literally true in photography. In my pre-photographic training (in other words when I was, like Pumba, a young warthog) I would tilt my head to look at things up close. Walking through the halls of my elementary school I would lean my head toward the wall, close one eye, and examine the wall's texture and paint as I pretended I was flying above the surface of a pocked and cratered planet, soaring to a higher altitude when approaching fire hydrants, doorways and water fountains. When I played with toys, I lay on the floor to get the best view of the rockets I sent into space as they lifted off and broke free from the constraints of gravity with a mighty roar and glorious plume of fire. I looked at the sky a lot as well, as I lay on my back in open grassy places, until it would occur to me that if gravity were to fail there was nothing nearby to grab hold of as I floated off into the sky. That's when I would find a tree to lie under.
In my adulthood I have continued these practices (when other adults aren't looking) just to see what familiar things look like from unfamiliar angles. Once, when giving blood for some sort of something-or-other, I leaned my head down onto my arm to catch a closer and different angle on that precious red stuff bubbling up into the tube. My attendant, thinking I was fainting (never done that, though), became alarmed.
"I'm just getting a different viewing angle," I replied. "It looks really cool from down here." I managed to talk her out of giving me a mental exam.
Photographing an object from a close vantage point versus a far vantage point creates a very different view of that same object (and the surrounding areas) when that object is captured at the same size in the photo. Here's an example of a wide shot:
The photo above, taken up close to the marker with a wide angle lens, shows a lot of the cemetery behind the marker, including the mausoleum it denotes. When I want to show an object in its context (such as the #30 marker with the mausoleum behind it) I use a wide angle lens. When, on the other hand, I want to separate an object from its background, I use a longer focal length lens. In the photo below, I backed away from the tour marker and used a 90mm telephoto lens, being careful to keep the marker the same size in the viewfinder.
As you can see, in photography what you see depends not only on where you stand, but also on the focal length of the lens you are using. The photos below, taken in some mysterious place somewhere on a planet orbiting our sun, demonstrate again that an object shown roughly the same size in the photograph, but taken with extremes of wide angle and telephoto, will be rendered with dramatically different perspective.
Let's get an even greater insight into perspective: when you're far from objects, it's hard to gauge their relative positions. Many are the times I've been driving up my street thinking from a distance that someone has parked too close to my driveway, only to see, when I actually arrive, there is plenty of space for me to pull into the driveway. Many people think that a powerful telephoto lens compresses the apparent distance between far-away objects, when in reality it is our distance from those objects that makes them appear to be closer than they are. Here are two photos of the premier city of the midwest taken from the same vantage point but with different lenses. These illustrate the point just made:
One last thing; a perspective control lens (now commonly called a tilt/shift lens) allows you to get rid of the "falling over backwards" phenomenon caused by tilting the camera up or down to get everything into the photo. We call what you see in the photo below "converging parallels" or "converging verticals".
Both Nikon and Canon make a variety of tilt/shift lenses for their DSLR lines, and anyone who wishes to do architectural photography should own a couple of these great lenses. Here are two more photographs that were taken with a tilt/shift lens that show how distance from the subject affects perspective:
Note on the lower photo how much more of the drum of the dome is visible. Moving the vantage point further from the building allows us to see more of the building. Our perspective has changed.
What you see depends on where you stand.