In both effects the treatment is extremely simple, yet in the one, when the light comes from behind, simplicity and directness are the more strictly necessary; indeed, in painting a subject with the light from the back, the energy of the painter should principally be directed to the gradation of the shadows from misty distance to direct foreground, having as few lights as can be dispensed with for the sake of form.
In the other, the time of day must be considered with the direction of the light, so that it may pass directly and consistently throughout all parts of the picture.
There is one strict rule I would have you bear in mind when sketching outside; remember that the whole of your picture only represents a second of time, the flapping of a drop-shutter over an instantaneous plate. It will never be like nature if the light upon one part falls half an hour before the light falls on another portion; so in planning out the dispositions of your light you must do as the photographic camera does. Fix one second upon the plate of your memory all over the scene, and try to work up to this second.
The mechanical worker, who thinks he is a much more conscientious artist and lover of nature than the impressionist, because he sits down with his palette and canvas to his easel before nature six or ten hours at a stretch, is much more unfaithful, even to the image he so patiently tries to copy, than the impressionist, who, glancing rapidly and comprehensively round, makes a few swift notes, catches the spirit of the effect, and depends upon his memory, or a faithful photograph of his image, for his detail afterwards. We may blink at this as much as we choose, yet pre-Raphaelitism must come to its proper place in good time, and be shut in with the antique casts of the schoolroom, with the young men and women student days, shut in along with their cross-hatchings and point-stipplings, to be laid carefully in their boxes along with their gold, silver, and bronze medals, and other school prizes, when they come out to face flesh and blood, broad daylight, and the world that will not wait upon the crochet-meshes of meaningless patience.
I would not have a painter work a single line without having a direct meaning for that line—not only a direct meaning, but a very potent intention, which cannot be laid aside without injuring all the other parts of the composition; so in lighting, I wish to impress upon all the necessity for the strictest economy in the placing of the lights and shadows; too much protestation will ever weaken an assurance, so also too many lights will destroy the effect of light.
The other day I passed along a road when the sun was shining, a broad daylighty forenoon sun-effect, and yet that stretch of road only received the full force of it on one portion; silver-grey it spread from my feet into distance; in mid-distance it took the gleam of quicksilver upon it, growing blue-grey as it receded, and fawn-coloured as it neared me, darkening with the ruts and markings of the foreground—detail always produces darkness unless the light shines full and nearly upon it, and then it will be full of acute shadow and strong light.