"Innenperspektive", illustration from "Beiträge zur Analyse der Empfindungen", by Ernst Mach, 1886, G. Fischer
Your ability to draw what you see is limited by your ability to see. Vision is not simply a mechanical process that is naturally perfect. Seeing takes place more in the brain than in the eyes, and it can be transformed and expanded by serious practice, just like any other skill that involves the interaction of body and mind.
The complexities of human visual perception, and techniques for training or honing your vision, are a topic for a whole book. This post offers a collection of links and ideas as a very basic introduction.
If you’re up for an experiment, this link describes a “Selective Attention Test” involving counting basketball passes in a video. Read the description and then take the video test before reading further.
Part of learning to see is simply learning to notice things. Most people actually notice very little of what passes before their eyes. What they do see is what they have been taught or told to pay attention to. Stage magicians can make you not see something simply by directing your attention to something else. (Unfortunately marketers and politicians have also mastered such manipulations of attention.)
Cover of "Pilgrim at Tinker Creek" by Annie Dillard, first edition, 1974, Harper's Magazine Press
In the classic Pilgrim at Tinker Creek, Annie Dillard writes eloquently about learning to see in the natural world. Dillard is a poet, philosopher, artist, and keen observer of nature. Her words helped awaken me to the rich and strange mystery of seeing. Read chapter 2, titled “Seeing”, or better, get the book and treat yourself to one of the literary masterpieces of our time. Learning how to see more and better is a primary concern of the whole book.
Nearly any craft or specialty involves learning to see what most eyes would miss. For example, the ancient Polynesian navigators, who crossed thousands of miles of ocean in simple boats without any instruments, learned to see land beyond the horizon by observing light reflected on the bottoms of clouds. Noticing and naming the phenomenon awoke their vision to it.
Surface Anatomy of the Back, fig. 477 from "Applied Anatomy: The Construction of the Human Body", by Gwylim G. Davis, 1913, Lippincott
This is why figurative artists study anatomy. When you learn the names and locations of bones and muscles, you can see them because you know what they are. The subtle and sometimes confusing bumps and curves on the surface of the body are more clearly seen because you understand them as manifestations of an underlying structure.
But there’s a contrary principle. Sometimes what you know can actually make it hard to see what you see. For example, you know that the legs, for instance, are long shapes. But when they are foreshortened, that is, when they face you along their axis, they may not appear long at all. Thinking of the leg as a long shape may interfere with your ability to see it as a foreshortened, oval form. So there are cases in which you need to forget what you know in order to draw what you see.
"The Dead Christ" by Andrea Mantegna, c. 1480
The illustration at the top of this post is from The Analysis of Sensations and the Relation of the Physical to the Psychical, by Austrian physicist and philosopher Ernst Mach, whose name has become the scientific term for the speed of sound. Mach’s philosophy starts from the idea that all we can know, we know via the senses, so understanding how the senses work is fundamental to understanding anything. In the illustration, he is attempting to represent the view from inside his head, through his left eye. You can see his nose and mustache to the right of the eye socket. This is a pretty good representation of what you can see with one eye, sitting in one place, keeping the head still, but moving the eye around.
Everything in the Mach illustration is in sharp focus. If the eye does not move, only a tiny fraction of what it takes in is actually seen sharply. The fovea is a dense cluster of light-sensitive cells in the center of the retina, the image-receiving surface in the eye. The fovea sees in high-resolution and full color, but it only covers a very narrow spot of the complete field of view of the eye. The eye does take in close to a 180 degree view, but away from center it becomes increasingly lower-resolution and less sensitive to color. If you could capture a snapshot of sensor output from the retina for a single instant, it would look something like this simulation:
Rough Simulation of Foveal and Peripheral Vision, illustration by Fred Hatt derived from "Fisheye Domilise's", photo by Editor B
The eye provides a wide-field view, like a photographer’s fisheye lens, but not very sharp, superimposed with a very sharp narrow-angle view like that of a telephoto lens. The wide view, or peripheral vision, is useful for noticing movement coming from any direction, and for orientation and aiming of the foveal center of attention. Of course we’re just describing the raw data coming in from the eye. The eye scans about and the visual cortex, or image processing center of the brain, knits all of this moving data together into a seemingly sharp view of everything. But fix your eye on one word on the page of a book and see if you can read a word a few inches away without moving the eye, and you will see that the area of sharp vision is quite small.
In observational drawing, we’re using these eyes, a sharp foveal scanning element combined with an unsharp peripheral image. The foveal vision cannot see the whole shape or composition, just one small area at a time. The peripheral vision can see the whole shape but without much clarity.
Certain practices and exercises can train you to make better use of this dual data stream. Artists understand this instinctively. Often you’ll see artists squinting at their subject or at their work. Squinting is a way of partially disabling the foveal vision, throwing the whole visual field out-of-focus. Since foveal input usually dominates the processing functions of the visual cortex, disabling the fovea allows attention to take in more of the peripheral view. This can help you to see the whole general field at once, understanding it as a simplified and unified shape. If you are an artist trying to turn vision into a picture, that is just what you need. It helps you to see compositionally, and to maintain proper proportions and spatial relationships.
I do many practices to improve my visual perception, not just when I’m drawing but when I’m moving about in the world. For example, I squint or cross my eyes to bring awareness to my peripheral view when I’m walking down the street. It is not unsafe, as your peripheral perception, important for navigation and collision avoidance, is actually heightened when you’re doing these things. Still, I don’t advise doing it while crossing a street as the unfamiliarity of looking at the world this way could be disorienting.
I also use photography as a tool for honing perception. If you carry a camera with a single focal-length lens, not a zoom, you will learn to look for images that fit within the angle of view of that lens. Your brain will be composing your visual world into a rectangular frame as you look at it. You are learning to see the world in terms of compositions and patterns, another vital skill for an artist.
Whether you are an artist or not, exercises to improve your ability to perceive the world can open you up to more of the beauty the world has to offer, and can liberate you from some of the marketers’ attempts to manipulate what you notice.
Illustrations in this post link back to their original online sources.