The Sight-size Method
When using sight-size, the canvas is placed next to the sitter so that both appear the same size when viewed together from a given distance. In this way, shapes and proportions, colours and values can be evaluated to scale alongside nature. First documented by Roger de Piles in 1708, sight-size is primarily a portrait practice (Reynolds, Raeburn, Sargent etc.), but it is also the best way to train the eye and therefore fundamental in an educational context.
Roger de Piles ‘The Principles of Painting’ 1743:
The portrait being now supposed to be as much finish’d as you are able, nothing remains, but, at some reasonable distance, to view both the picture and the sitter together, in order to determine with certainty, whether there is anything still wanting to perfect the work.
Lady Burlington on Reynolds:
… he took quite a quantity of exercise while he painted, for he continually walked backward and forward. His plan was to walk away several feet, then take a long look at me and the picture as we stood side by side, then rush up to the portrait and dash at it in a kind of fury. I sometimes thought he would make a mistake, and paint on me instead of the picture.
On Henry Raeburn:
… and then having placed me in a chair on a platform at the end of his painting-room, in the posture required, he set up his easel beside me with a canvas ready to receive the colour. When he saw all was right, he took his palette and his brush, retreated back step by step, with his face toward me, till he was nigh the other end of the room; he stood and studied for a minute more, then came up to the canvas, and, without looking at me, wrought upon it with colour for some time.
William Rothenstein on John Singer Sargent:
Sargent, when he painted the size of life, placed his canvas on a level with the model, walked back until canvas and sitter were equal before his eye, and was thus able to estimate the construction and values of his representation.