Why measuring angles is a good idea

Why should you measure angles instead of distances or proportions? Here are a couple of common methods of taking measurements for a life drawing. We'll discuss their properties and see why measuring angles instead might be a good idea.

1) Proportional measuring.

The most common method. First choose some distance as a unit, say, the size of the head. Then measure how many units there are from, say, the head to the navel. As all students have found, even with considerable practice this doesn't work all that well. Some problems are:

a) All measurements are only precise up to about half the size of the unit you chose. Every measurement will be "oh, a little bit more than 2 heads", or "about 3 and a half heads". A little bit more here and a little bit less there and soon nothing fits together.

b) As Robert Fawcett (a proponent of sight-size) pointed out, you don't want to do algebra in your head while drawing. You want to use your eyes and compare what you draw to what you see. Since you have to make a conversion of your unit in order to fit the drawing on the paper, you are constantly doing distracting translating work: "So, it's (about) three units...and a bit more than a half... on the model, and each unit on my paper is the size of this reference here, so I'll draw this reference size three times...(and about a half and a bit more)"

c) This more or less works when the measuring is on the same (vertical or horizontal) axis. But few things will be on that axis. Either you will have to measure angles anyway and distances along those angles (and , then why measure distances at all, since, as we shall see, angles are enough) or you will effectively have to draw in an imaginary grid, in order to relate horizontal to vertical distances. Failure to do this properly results in squashed up or elongated figures (a commonly observed problem).

2) Sight-Size.

In the sight-size method you set things up so that the model looks the same size as the picture, so all you have to do is compare by eyesight and make alignments. Sightsize solves most of the problems of the proportional method. One common objection to sight-size is the fact that most setups look cumbersome and slow (and boring!) to use, but that is an accidental feature of a certain atelier culture usually associated with sightsize. Such cumbersome setups are a type of (very accurate) sightsize, but you can use very useful and light setups for sightsize, the choice is yours. There still remains a real objection, though:

a) Sight-size is nice...when you can have it! Which outside of the studio isn't always the case. You have to place the paper vertically, place the subject at the right distance for the size of the drawing you want. Sometimes that is just impossible or requires you to do a lot of walking (or driving) to get closer or further away from a big target (and then you lost the spot you wanted) or if you want to draw a head life-size you have to place the drawing next to it and walk back and forth all day long to make changes and spot differences. You can always spot a sight-sizer by the tracks he leaves on the carpet. Sorry, not for me. Sight-size substitutes a lot of thought-work for a lot of footwork. :) I want to draw from whatever spot I choose, I want to draw spontaneously, in any scale, with no complicated setups, and with accuracy.

3) ANGLES: Here is the beautiful thing about angles:

a) Angles are always sightsize! From any distance! This is beacause angles are invariant for a change of scale.
Take a rectangle, for instance. Suppose the angle along the diagonal is 80 degrees (a tall rectangle, maybe a building seen head-on). Now move away from it, or move closer. The rectangle will look twice as big, or twice as small, or two thirds ("and a bit!") bigger, but what happens to that angle? It stays the same! Angles are always sight-size! All you have to do, at any scale you choose to draw, is check visually if your angles are equal to the ones on the model. You get the advantages of sight-size mehtods but you can stand at any spot!

b) No need to relate measurements in two different axis as a special problem. Just check angles to the vertical and obtain the distance measurements automatically. (How? Triangulation does it. With a simple drawing method, not by calculation. We'll see how ahead)

c) Measuring angles is easy to do (after some required training), requires no special apparatus, and no special limiting set-up. This is the hardest part, actually, but there are many tricks that I've developed over time and that I'll try to teach in this series of posts, after dealing with triangulation itself. Some of the ways of measuring angles can be used to draw on a vertical plane, some can be used to draw on your lap (great for drawing impromptu on the field and so on) and some are memory/observation based, not requiring any visible act of measurement (great for drawing without calling attention to yourself - you don't want to raise an arm to take measurement when drawing someone on the subway!)

d) Measuring angles does not have the "and a bit more" problem of the proportional method. The error you make in each angle measurement is not a fraction of some arbitrary unit of measurement taken from the model, it is a fixed error that only depends on your ability at angle measurement - so, it should become smaller with training, and has no arbitrary, model-dependent lower bound. Judicious choosing of the angles to measure should improve it even more (as surveyors well know).