Most of us have probably heard about the whole right brain, left brain thing. You know: the left brain is the coldly analytical, number-crunching, science-and-math whiz, and the right brain is your spacey, boho flower child, full of creativity, emotion, and bright colors; good with language, drama and art. And when most of us conjure up a visual for the term 'artist', the flower child, or maybe the angst-ridden, black-garbed nihilist, suffering for the art, oh, lawdy, pops up. Not to say these stereotypes aren't out there walking the art community (I probably roomed with a few in art school), but what do you do if you'd really like to learn to draw, but you are, oh, a rocket scientist, or an accountant? Are you slap out of luck?
Why no, of course not. One of the most famous artists in history, Leonardo da Vinci, was very much in touch with his left brain, designing extremely advanced technological gizmos, like tanks, and even a helicopter! Leonardo was no slouch in the art department, obviously, but one of the strengths of his draftsmanship (drawing skill) was his rather scientific observation of his subjects, most specifically the human figure.
See, Leonardo figured out that human beings, while varying greatly in size, shape, appearance and character, still adhere to some very standard rues of proportion, and he left us a famous drawing, "Vitruvian Man", to illustrate clearly what he'd hit upon. Take a look at Vitruvian Man: an adult male figure is shown standing with arms extended in different positions, and with legs similarly shown in different positions. He is shown inside two basic geometric shapes, a circle and a square, and his major joints are indicated with bisecting lines. This illustration depicts what I like to call "wacky secrets of proportion", which your formula-following left brain will appreciate, as you can apply these mathematical principles to all of your drawings of people.
Why did Leonardo draw Vitruvian Man inside a circle? This one is pretty easy; as you may note from the different arm and leg positions shown in the drawing, the rotation of our limbs describe a perfect arc (I call this the "Snow Angel Principle"). This is interesting, but might not help so much with the drawing, so let's move along to the next question: Why did Leonardo draw our friend inside a square? Well, now, here's an interesting fact: Notice that Vitruvian Man's head and feet touch the top and bottom of the square, and that his fingertips touch each side. Remember, a square is an equilateral shape: all sides measure the same. That means, kids, that the distance from fingertip to fingertip is the same as from head to foot. Yeah, that's right: your wingspan is the same as your height, you big square, you!
There are other equal proportions on the human body, as well. Look at the major joints of the arm-shoulder, elbow, wrist. The elbow falls exactly between the shoulder and the wrist, which means that the upper arm is the same length as the lower arm (don't count the hand). Same thing goes for your lower limbs: with the knee at the exact midpoint, the upper and lower legs (don't count the feet) are the same length. Wacky, huh? Another interesting fact is that when your arms are hanging loosely at your sides, your elbows hit exactly at your natural waist. Many people draw the elbows too high. Furthermore, you can check the proportion of the head to the rest of body using the knowledge that the average adult is 7 ½ heads tall (including the head itself). Children, whose heads are proportionately larger, are fewer heads tall, varying with age. If you think your drawing of a child looks too old to be your subject, check to make sure you didn't make the head too small in proportion to the body.
One more thing about body proportions: Hands and feet are bigger than you think. Your hand can pretty much cover your entire face, and your feet have to hold your whole body up, so you'd better be happy about your big ol' gunboats, because they're keeping you from doing a face-plant. Here's a wacky secret of proportion that might win you some bar bets: Your foot is the same length as your arm from wrist to elbow (and hence, from elbow to shoulder, but it's a lot easier to check against your lower arm). Seriously! Go ahead and check for yourself; I'll wait.
And wacky secrets of proportion aren't just for the body; there are plenty of things going on in your face and head, too! For example, on a person who is looking forward with his head straight up and down, you can divide the face evenly with a vertical midline and a horizontal midline; a plus sign, more or less, except the head is taller than it is wide, of course. The typical (unbroken) nose will run right down the vertical midline, which will evenly bisect eyes, brows, nose, mouth and chin. The eyes will sit right on, not above, the horizontal midline. That's right: your eyes are exactly halfway up your head. It's a very typical mistake to draw the eyes too far up. Don't forget, you need a lot of skull space to hold your big ol' brain! For kids, the cranium (brain case) is even bigger in proportion to the face (their eyes are bigger, too).
For adults, the eyes are exactly one eye-width apart, the pupils when looking straight ahead generally line up right over the corners of the mouth, the inner corners of the eyes tend to be right above the nostrils, and even your ears get a wacky rule: They are the exact length, from tip to lobe, as your nose, from brow to tip.
So, left-brainers, never fear; even though you should try to tap into your right hemisphere when you cozy up to your drawing board (to do this, try stimulating other senses besides the visual: burn a nice-smelling candle, sip some fragrant tea, listen to some music you like), you can still rest knowing that even a complicated subject like the human body still has to fit a set of guidelines that's actually pretty easy to learn. So go ahead, you doctors, lawyers, and IRS agents! You, too, can have art in your lives! Get to sketchin'!
Here is another article you may enjoy on figure drawing: http://allsortsartbyali.blogspot.com/2015/03/i-have-been-professional-portrait.html