Perspective is an important part of composition. But having a through understanding of different possibilities of perspective is important. For this discussion we should stick to some basic mechanics.
There are two…
When it comes to perception in relation to photography there are two factors, perspective and magnification. Perspective is the location and angle of the camera in relation to the subject and it’s background. Magnification is the size of the subjects within the frame. We must distinguish between these two concepts for this discussion. This is because you can change the magnification without a change in perspective, as well as the reverse. Let’s play a little bit of a game for this discussion. Take a hand, make a peace sign and hold it a little ways away from your face, close an eye. You can clearly see your hand and whatever is falling between your fingers. Now close that eye and open another, there should be something else visible between your fingers now. This is a shift in perspective, the distance between your eyes has effected the angle of viewing. Now with one eye move your head side to side. The hand should be moving rapidly and the background less so, this is another perspective on perspective. Now if you were to use your other hand to hold a magnifying glass and held your hand steady and magnified it, everything in the field of view would be magnified equally. There is no change in the relation of angles between you, the hand, or the background it is all simply larger. So take that and chew on it for a little bit.
Something, something, darkside……
So lets relate that mess back to photography. If you chewed your way through my thought experiment and didn’t get too confused we shall continue. Go find your tripod, if you do not have one then smack yourself and go and buy one.
Take the tripod and set it up where you have a foreground and background objects. The background needs to be a good distance off such as a mountain, sand dune, or distant barn. The foreground object should be something like a tree and within the range of 30 feet or so. Using a short lens (short lenses are those that have a shorter focal length than a “normal lens” which is usually about 50mm, or the diagonal of the photosensitive medium) photograph both two objects, switch lenses to one that is double the focal length, and then again to one that is double that focal length. Now repeat this process 1/2 the distance to the foreground object, and 50 feet to both sides of your original position. In all cases keep the tree in roughly the same location in the frame. Now find something else to photograph for a while or go home.
Download, develop, or print your photographs and examine them all. Set them up if you printed them in a way so that you can see their positions and the differences. Whenever you double the focal length of the lens a 2x magnification occurs of the entire frame, so your tree and background will all be magnified. When you change position the tree will appear to move, and the background will remain fairly unchanged. Distant objects will barely change perspective, remember that. So in the case where you moved 1/2 the distance to the tree, it will appear larger and the background will still remain the same. With the side to side shift there will be different angles on the tree, and yet again the background will barely change. You will notice this same thing when driving a car, the trees will fly by but that large distant object barely seems to move. This is because the further the object is, the less of an viewing angle you have on it.
It probably exist, somewhere…
I imaging that somewhere there is a formula that can relate distance and the perspective shift, and it probably involves geometry and calculus. But in the interest of keeping this simple I shall create some sort of mathematical relation on the spot. The percentage of the distance to the subject that change your position by is equivalent to the shift in perspective. Therefore if you are 100 yards from the subject and you move 5 yards to the side, that is a 20% shift of your position relative to the distance to the subject, therefore you can expect a 20% shift in perspective. This is more than likely no where near numerically accurate, but it will keep your mind engaged when shooting which is good enough for me. I shall develop a formula at some point, or find one. Using this “formula” it is easy to understand that the mountain range that is 10 miles away dose not shift perspective when you move 50 feet to the side, but the tree that is 30 feet away has an immense shift. This would be a 0.117% shift for the mountains, and a 167% shift for the tree. This is an easy to remember rule that is accurate enough for this purpose, so use it.
Get out there and shoot, play with perspective. Fiddle with the manual settings, buy a fraking tripod! Question everything! Shoot only what is interesting!
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