These tone values are only to be perceived in their true relationship by the eye contemplating a wide field of vision.  With the ordinary habit of looking only at individual parts of nature, the general impression being but dimly felt, they are not observed.  The artist has to acquire the habit of generalising his visual attention over a wide field if he would perceive the true relation of the parts to this scale of values.  Half closing the eyes, which is the usual method of doing this, destroys the perception of a great deal of colour.  Another method of throwing the eyes out of focus and enabling one to judge of large relationships, is to dilate them widely.  This rather increases than diminishes the colour, but is not so safe a method of judging subtle tone relationships.

It is easier in approaching this study out of doors to begin with quiet effects of light.  Some of those soft grey days in this country are very beautiful in tone, and change so little that careful studies can be made.  And with indoor work, place your subject rather away from the direct light and avoid much light and shade; let the light come from behind you.

If very strong light effects, such as sunlight, or a dark interior lit by one brilliant window, are attempted, the values will be found to be much simpler and more harsh, often resolving themselves into two masses, a brilliant light contrasted with a dark shadow.  This tone arrangement of strong light in contrast with dark shadow was a favourite formula with many schools of the past, since Leonardo da Vinci first used it.  Great breadth and splendour is given by it to design, and it is one of the most impressive of tone arrangements.  Leonardo da Vinci’s “Our Lady of the Rocks,” in the National Gallery, is an early example of this treatment.  And Correggio’s “Venus, Mercury, and Cupid,” here reproduced, is another particularly fine example.  Reynolds and many of the eighteenth-century men used this scheme in their work almost entirely.  This strong light and shade, by eliminating to a large extent the half tones, helps to preserve in highly complete work a simplicity and directness of statement that is very powerful.  For certain impressions it probably will never be bettered, but it is a very well-worn convention.  Manet among the moderns has given new life to this formula, although he did not derive his inspiration directly from Correggio but through the Spanish school.  By working in a strong, rather glaring, direct light, he eliminated still further the half tones, and got rid to a great extent of light and shade.  Coming at a time when the realistic and plain air movements were destroying simple directness, his work was of great value, bringing back, as it did with its insistence on large, simple masses, a sense of frank design.  His influence has been very great in recent years, as artists have felt that it offered a new formula for design and colour.  Light and shade and half tone are the