ON THE DISTINCTION BETWEEN SIMULTANEOUS, SUCCESSIVE, AND MIXED CONTRAST OF COLOURS, AND ON THE CONNEXION BETWEEN THE EXPERIMENTS MADE BY THE AUTHOR, AND THOSE PREVIOUSLY MADE BY OTHER OBSERVERS. DISTINCTION BETWEEN SIMULTANEOUS, SUCCESSIVE, AND MIXED CONTRAST OF COLOURS.
77. Before speaking of the relation of my experiments to those made by others on the contrast of colours, we must distinguish three classes of contrast. The first includes those relating to the contrast which I term simultaneous; the second to that which I term successive; and the third to that which I term mixed.
78. Simultaneous contrast of colours includes that phenomena of modification which objects variously coloured seem to undergo in physical composition, and in the depth of tone of their respective colours, when seen at the same time.
79. Successive contrast of colours includes the phenomena observed when the eyes having looked for some time at one or more coloured objects, perceive, after having ceased to look at them, images of those objects, presenting the colour complementary to that of the actual object.
80. This distinction also facilitates the understanding of the phenomena which maybe called mixed contrast; for, the retina having seen a certain colour for some time, has an aptitude to see for a further time the complementary of that colour, as well as any new colour presented by an external object; the sensation perceived being the result of this new colour, and the complementary of the first.
For want of this distinction, one of the branches of optics most fertile in applications, has not been treated with the clearness and precision which are necessary to show its importance to those who have not experimented upon it.
81. The following is a simple mode of observing mixed contrast:—Having closed one eye, the right for example, look steadily with the left at a sheet of paper of a colour A; when this colour seems to become dull, look immediately at a sheet of paper of the colour B, the eye then has the impression produced by the mixture of this colour B with the complementary (C) of the colour A.
82. To be convinced of this mixed sensation, it is only necessary to shut the left eye, and to look at the colour B with the right eye; when the sensation perceived is not only that of the colour B, but it may appear modified in the contrary way to that of the mixed sensation C + B, or what is the same, it appears to be rather A + B.
83. Upon shutting the right eye, and looking again at the colour B with the left eye, and that many times in succession, different sensations are successively perceived, but more and more feebly, until at length the left eye returns to its normal state.
84. I advise any person who thinks that one of his eyes is more able to perceive colours than the other, to look at a sheet of paper alternately with the right and left eye; if the sensations of each are identical, he may conclude that he has deceived himself. And even if the sensations be different, the experiment should be repeated several times, successively, for the difference observed in a single experiment might be occasioned by one of the eyes having been previously modified or fatigued.
85. This practice appears to me especially useful to painters. I now give some examples of mixed contrast.
86. The left eye, having looked for some time at red, has an aptitude to see afterwards green, the complementary of red. If then it be attracted by yellow, it perceives a sensation resulting from the mixture of green and yellow. The left eye being shut, and the right eye, which has not been modified by the sight of red, being opened, it sees yellow, and it is possible that this yellow may appear more orange than it is really.
| 87. | If the left eye had first seen |
and had afterwards seen |
the latter would have seemed |
| Yellow | Red | Violet. | |
| 88. | Red | Blue | Greenish. |
| 89. | Blue | Red | Orange-red. |
| 90. | Yellow | Blue | Blue-violet. |
| 91. | Blue | Yellow | Orange-yellow. |
| 92. | Red | Orange | Yellow. |
| 93. | Orange | Red | Red-violet. |
| 94. | Red | Violet | Deep blue. |
| 95. | Violet | Red | Orange-red. |
| 96. | Yellow | Orange | Red. |
| 97. | Orange | Yellow | Greenish-yellow. |
| 98. | Yellow | Green | Bluish-green. |
| 99. | Green | Yellow | Orange-yellow. |
| 100. | Blue | Green | Yellow-green. |
| 101. | Green | Blue | Blue-violet. |
| 102. | Blue | Violet | Reddish-violet. |
| 103. | Violet | Blue | Greenish-blue. |
| 104. | Orange | Green | Bluish-green. |
| 105. | Green | Orange | Reddish-orange. |
| 106. | Orange | Violet | Bluish-violet. |
| 107. | Violet | Orange | Yellowish-orange. |
| 108. | Green | Violet | Red-violet. |
| 109. | Violet | Green | Yellow-green. |
| 110. | Red | Green | Bluer. |
| 111. | Green | Red | Tinted-violet. |
| 112. | Yellow | Violet | A little bluer. |
| 113. | Violet | Yellow | Greenish. |
| 114. | Blue | Orange | Yellower. |
| 115. | Orange | Blue | More violet. |
116. I should observe that all these colours, at least to my eyes, did not undergo equally intense or equally continuous modifications. For instance, the modification produced by the successive view of yellow and violet, or of violet and yellow, is stronger and more durable than that produced by the successive view of blue and orange, and still more than that of orange and blue. The modification produced by the successive view of red and green, of green and red, is but slight, and not enduring.
I may also add that the depth of tone exercises some influence on the modification; for, if after looking at orange, we look at dark-blue, the latter will appear greenish rather than violet, a result contrary to that afforded by a light blue.
117. I have thought it the more necessary to mention under a special name the phenomenon which I call mixed contrast, as it explains certain facts remarked by dealers in coloured fabrics, as well as the inconvenience felt by painters, who, wishing to produce an exact imitation of their models, look at them so long as to be unable to perceive their tones and modifications. I will mention two facts which have been communicated to me by manufacturers, referring the reader to Part II. for the application of the study of mixed contrast to painting.
118. First Fact. When a purchaser has looked a long time at a yellow cloth, and he is then shown an orange, orange-red, or scarlet one, he finds it dull, and judges it to be a dark or crimson-red; because the retina affected by the yellow has a tendency to see violet; and hence all the yellow of the orange colour disappears, and the eye sees it as a red, or a red inclining to violet.
119. Second Fact. If there be presented to a purchaser, one after another, fourteen pieces of a red fabric, he judges the six or seven last pieces to be less beautiful than the first, although they may be all identical. What is the reason of this false judgment? It is, that the eyes which have seen six or eight red pieces in succession, are in the same condition as if they had looked steadily for the same length of time at a single red stuff,—having a tendency to see the complementary of red, that is green. This tendency necessarily enfeebles the brilliancy of the red of the last pieces. The dealer, therefore, that he may not be a sufferer from the fatigued eyes of his customer, after showing him a few red pieces, should present some green ones, to restore the eyes to their normal state. If the view of the green were sufficiently prolonged to pass the normal state, the eyes would acquire a tendency to see red, and then the pieces seen last would appear more beautiful than the rest.