Turner and Mulready : the effect of certain faults of vision on painting, with especial reference to their works. The real and ideal in portraiture. The deterioration of oil paintings : three lectures / by R. Liebreich.

  • Richard Liebreich
Date:
1888
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Licence: Public Domain Mark

Credit: Turner and Mulready : the effect of certain faults of vision on painting, with especial reference to their works. The real and ideal in portraiture. The deterioration of oil paintings : three lectures / by R. Liebreich. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    white lines I make the experiment with coloured lines, it will show the mixing of colours produced by astigmatism; and if I now turn the axis of the lens, you will observe the effect of different forms of astigmatism. I show you here a square (Fig. 6) : if I added a cylindrical concave glass, with its axis placed horizontally, the square becomes an oblong. In order to show you how it is possible that the same eye may see an object at too great a distance elongated in a vertical direction, and, on the contrary, one that is too near enlarged in a horizontal direction, I need only place this cylindrical glass before or behind the focus of the apparatus without turning 1he axis, and you will then see the square, first elongated in a vertical direction (Fig. 7), and then enlarged in a horizontal direction. Fig. 6. Fig. 7. Lastly, I show you a portrait. Imagine to yourself that it repre- sents the person whom the astigmatical painter is painting ; then, by aid of the cylindrical glass you can form an idea how the painter sees this person. If I alter the position of the glass, the portrait assumes the form in which the painter sees his own painting on the canvas. This will explain to you why he paints the portrait still longer than he sees the person. With regard to an anomaly of sight, which seems almost foreign to the subject of painting—I mean colour-blindness—I will also say a few words here, as the subject seems to be regarded with particular interest in England. What we call colour-blindness is a congenital defect of vision, which is characterized by the absence of one of the three primary sensations of colour. The primary sensations of colour are red, green, and violet, according to Thomas Young and Helmholtz; or
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