There is no such thing, for our purposes, as accuracy of vision. It is not so much that we don't all see alike. We don't. But nature is constantly moving and changing all the time. What we see rapidly alters from minute to minute.
All we can do is to compromise between the movement of life and the static nature of our rectangle of paper or canvas. We can only aim at a generalization, at most, of the scene before us, or a distillation of the character we can observe or feel. Nature is complex; never still, guarding her secrets closely. We won't be able to make her give those secrets up, as the Pre-Raphaelites wrongly thought, by copying her with minute accuracy. Instead, we must take her unawares — almost casually, in fact, and then some of her spirit will infuse our efforts.
What I have just said will again help you to understand what some modern artists are aiming at. When you see their apparently distorted visions, you will come to realize that they, too, are trying to find that exact equivalent between painting and reality. Through a study of nature, by drawing and painting yourself, you will begin to understand the problems involved and be able to assess the work of others better (Fig. 21).
It is an easy mistake to make, to think that accuracy, or getting things 'right' is one of the aims of an artist. A thing can only be 'right' according to you and how you see it. Accuracy under the conditions stated, of an ever-changing ever-moving, ever-complex nature is impossible. However clever you may be, you won't be able to compete. What is at stake is not being accurate but getting pleasure from observing these changes and movements in nature and trying to express them on paper in your own way.
One can write volumes about the problems of eye-levels, vanishing points and all the other paraphernalia concerned with perspective. Frankly, I think it is best ignored. It will only muddle your eyes and lead you into all sorts of misconceptions.
Perspective is at best a device for the use of architects who wish to impress their clients with their drawings and need not seriously concern an artist. Use your viewfinder to assess any sloping of angles on buildings or streets and roads. If you put down what you see, it will not only look in perspective, it will, in all probability, be in perspective. Get used to noting how angles change with a new viewpoint.
Note how things look different when you are high up and when you are down low. If you pay particular attention to these changes you will be understanding perspective and what happens without a lot of unnecessary theory.