Sketching Drawing - How to Obtain Correct Proportions

Realistic drawing relies on obtaining the correct proportions of a scene or subject in your drawing. This is especially true of portraiture where a good likeness is the main aim. Let's look at a method for obtaining correct proportions in your drawings.

What are proportions?

Proportions are about size relationships. When we compare the size of one object to the size of another object we are checking the difference in the sizes of the two objects. This difference in size can be expressed as a proportion, e.g. one of the objects may be twice the size of the other. Proportions can be expressed in different ways; we can use percentages 'Object A is 50% bigger than object B', or numbers 'Object C is twice as big as object A', or ratios 'Object D has a 3:1 ratio to object B'. In drawing it is usually easiest to use the numbers system (which may include fractions i.e. Object B is one half the size of object A).

Proportional relationships

From any given viewpoint, the sizes of the objects in the scene are normally fixed. If, from your chosen viewpoint, object A appears to be twice the size of object B then this relationship will usually remain fixed. From the same viewpoint, another object, object C, may appear to be one half the size of object B, in which case we know for sure that object C must be one quarter the size of object A. These are the proportional relationships and for a realistic rendition of the scene these relationships must be transferred accurately to the drawing paper. The proportional relationships in a scene are actually a visual phenomenon based on your viewpoint and are not necessarily related to the actual sizes of the physical objects in the scene. For example, it is quite possible for a tennis ball to be visually larger than a football if the viewpoint is sufficiently close to the tennis ball and the distance to the football is great enough. Remember: proportional relationships are firstly dictated by the viewpoint in relation to the scene and secondly by the physical size of the objects in the scene.

Getting the proportions right

The key to obtaining correct proportion in your drawing is to choose one measure (the length, width or height of something) in the scene, or on the subject, and use this to measure everything else in the scene. This first measure is your subject basic unit (the SBU) and you find the size relationships of other objects in the scene by comparing them to your SBU. For example, if you choose the width of a door as the SBU you can find the correct proportion of the door width to the door height by counting how many times the SBU goes into the height. For example, you may find that the height of the door is two and one half SBUs high; this tells you that the proportional relationship of the height of the door is two and one half times its width.

If we correctly draw the width of the door on our drawing paper at the size we need and in the correct position in the drawing format, we have produced a drawing basic unit (the DBU) that matches the SBU. We can then use the proportional relationship from the scene with our DBU to correctly assess the height of the door in the drawing. We then continue to use the SBU to measure all of the other important sizes in the actual scene and transfer them to our drawing paper using the DBU. In this way we maintain the proportional relationships of the scene in our drawing; the result will be a very accurate rendition.

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