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The laws of contrast of colour cover

The laws of contrast of colour

Chapter 7: CHAPTER II.
By M. E. Chevreul
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ArtScience - Physics

About This Book

A scientific and practical examination of colour contrast begins by defining simultaneous contrast and demonstrating it through systematic experiments and a representative formula, distinguishing simultaneous, successive, and mixed effects. It analyzes how colours alter one another when set beside white, black, grey, or related hues, presents chromatic diagrams, tones, scales, and rules of harmony, and offers detailed applications across painting, tapestry, dyeing, printing, dress, military clothing, illumination, and gardening. Practical rules for mixture and weaving — binary primary mixing, complementary mixtures, and three-colour combinations — accompany illustrative plates and guidance for achieving consistent colour relationships in decorative and pictorial work.

CHAPTER II.

The Law of the Simultaneous Contrast of Colours,
and the Formula which represents it.

16. After I had assured myself that the preceding phenomena were constant for my sight when it was not fatigued, and that many persons, accustomed to judge of colours, saw them as I did, I sought to reduce them to an expression sufficiently general to render it possible to predicate the effect which would be produced upon the organ of vision by the juxtaposition of two given colours. All the phenomena that I have observed seem to depend upon a very simple law, which in its most general sense may be enunciated in these terms: When two contiguous colours are seen at the same time, they appear as dissimilar as possible, both with regard to their optical composition and their depth of tone. Therefore there may be at once simultaneous contrast of colour, properly so called, and simultaneous contrast of tone.

17. Now two colours in juxtaposition, o and p, will differ from each other in the greatest possible degree when the complementary of o is added to p, and the complementary of p is added to o; indeed by the juxtaposition of o and p, the rays of the colour p, which o reflects when it is seen alone, and which are active in that case, cease to be so when o and p are in juxtaposition. Now under these circumstances, each of the two colours, losing what it has analogous to the other, must be so much more different from it.

18. The following formulæ will illustrate this:—

Let us represent—

The colour of the stripe O by the colour a plus white B,
”” P ” aʹ plus white Bʹ,
the complementary colour of a by C,
”” aʹ ” cʹ,

the colours of the two stripes seen separately are—

Colour of O = a + B; colour of P = aʹ + Bʹ;

by juxtaposition they become—

Colour of O = a + B + cʹ,
  P = aʹ + Bʹ + c.

We will now show that this expression amounts to taking away the rays of aʹ from the colour a of O (15), and to taking away the rays of the colour a from aʹ of P.

For let us suppose—

B reduced into two portions, white = b + white = (aʹ + cʹ),

Bʹ reduced into two portions, white = bʹ + white = (a + c).

The colours of the two stripes seen separately are—

The Colour of O = a + b + aʹ + cʹ, and the colour of
  P = aʹ + bʹ + a + c.

By juxtaposition they become—

The colour of O = a + b + cʹ, and the colour of
  P = aʹ + bʹ + c.

An expression which is evidently the same as the former, except for the values of B and Bʹ.

19. I have said that simultaneous contrast may at the same time affect the optical composition of colours, and the depth of their tone; consequently, when colours are not of the same depth, that which is deep appears deeper, and that which is light appears lighter; that is to say, the former appears to lose white light, while the latter seems to reflect more of it. Thus there may be, in looking at two contiguous colours, simultaneous contrast of colours and simultaneous contrast of tone.