This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Drawing; has been called the science of art, but artists have rarely approved the introduction of scientific methods in the study of drawing, fearing lest the use of formulas should lead to dull mechanical results. Students are left to discover methods and formulas of their own. It is true that every successful draftsman or artist has a method which he has worked out for himself, but he usually feels it to be so much a matter of his own individuality, that he is reluctant to impose it on students, who are likely to confound what is a vital principle with a personal mannerism, and by imitation of the latter injure the quality of personal expression which is so important in all creative work. So there is an inclination among drawing teachers to distrust anything which tends even to formulate the principles of drawing. Recently there has been, however, a distinct advance in the study of these principles, under the leadership of Dr. Denman W. Ross, of Harvard University, who has made it possible for the first time to speak with exactness of colors and values. As Dr. Ross has permitted the use of his valuable scale in this text book, it will greatly assist in making tangible and clear, what would otherwise be obscure and difficult to explain.
The word values as used in the text book refers entirely to relations of light and dark. For instance, the value of a given color, is represented by a tone of gray which has the same density or degree of light and dark that the color has. The value of a spot of red paint on a white ground is expressed by a spot of gray paint which appears as dark on the white ground as does the red paint. but from which the color principle has been omitted. A good photograph of a colored picture gives the values of the picture. A poor photograph, on the contrary, distorts the values and blues are often found too light, while reds and yellows will be too dark to truthfully express the values of the original color.