When a circle is seen from above or below your line of sight, the shape that you see is an ellipse. Ellipses look like flattened ovals. Correctly drawn ellipses can greatly enhance the illusion of reality in your paintings. Though it’s possible to draw them free-hand, I’ve found that it works better to construct them using this string and push-pin method.
The first step is to figure out what angle your ellipse is. In other words, how many degrees above or below your eye-level the circle you are drawing is. I use a home-made device using a stand, a string and a protractor. I describe it here Portfolio and Jewelry: Drawing. Next, determine the length of your ellipse (or the diameter of the circle). This is called the major axis of the ellipse. (The minor axis will be the height of the ellipse. We’ll determine that later.) Here, in my demo, I want a 25 degree ellipse whose major axis is 4 inches.
On a piece of paper, draw two intersecting lines, perpendicular to each other, and at least twice as long as your ellipse. Using a protractor, make a tic mark at 25 degrees, using the point where your lines cross as the center point.
Draw the line connecting the center point to your tic-mark.
I next mark the 4 inch major axis on my horizontal line, centering it on the vertical line. See below.
Next, using a compass, strike an arc from the center point to the end of the major axis (the circle’s radius), through the line showing the angle of your ellipse.
Measure the vertical distance from the intersection of these two lines to your horizontal line. Below, you can see it measure a little less than 7/8. “
Mark this same distance on your vertical line, both above and below the horizontal line. This total vertical distance is called the minor axis of the ellipse.
Now, using one of these marks, and keeping your compass set as it was to the circle’s radius, strike two arcs on the horizontal line. Where these arcs intersect the horizontal, will be your foci of the ellipse. This is where you’ll stick your pins.
Stick two push-pins into the drawing at the two foci. It helps if you have your drawing on top of a board so that you can stick the pins in firmly.
Cut a piece of string about 3 times longer than the length of the circle. Tie it around the base of the pushpins, as I am doing below. Your goal is to tie the string tightly enough that when pulled up tautly, the string will just touch either of the tic-marks you made on the vertical line.
The final step is to insert a pencil into the loop you made , and draw your ellipse while pushing to the outside, keeping the string taught. It can take a bit of tying and re-tying to get the string the correct length. Some string is a bit stretchy, so it might take some experimentation.
As you get close to the pins, it can be harder to draw accurately, but you can always correct free-hand!
Below is the finished ellipse, ready o be transferred to your canvas.
This same method works whatever the angle or size of the ellipse. It the ellipse is very small, it’s probably not worth the effort, and can be difficult to manage, but for most sizes, this works very well.