and observation, even to the most accomplished artist. "The finish of inconceivable minuteness," he says, "disturbs in no respect the repose of the masses, nor impairs in any way the general effect. The correctness of the lines, the precision of the forms in the designs of M. Daguerre, are as perfect as it is possible they can be, and yet, at the same time, we discover in them a broad and energetic manner, and a whole equally rich in hue and in effect. The painter will obtain by this process a quick method of making collections of studies, which he could not otherwise procure without much time and labour, and in a style very far inferior, whatever might be his talents in other respects." In the same spirit, Mr. Ruskin1 considers "the art of photography as enabling us to obtain as many memoranda of the facts of nature as we need ;" and long before Mr. Talbot taught us to fix upon paper the pictures of the camera obscura, the Rev. John Thomson, one of the most distinguished of our Scottish landscape painters, studied, in one of these instruments, the forms and colours of the scenes which he was to represent. Other artists, both in portrait and in landscape, now avail themselves of photography, both as an auxiliary and a guide in their profession; but there are certain difficulties and imperfections in the art itself, and so many precautions required in its right application, whether we use its pictures single, as representations on a plane, or take them binocularly, to be raised into relief by the stereoscope, that we must draw from the principles of optics the only rules which can be of real services to the arts of design.

In painting a landscape, a building, a figure, or a group

1 Modern Painters, vol. iii., Preface, pp. 11, 12.

of figures, the object of the artist is to represent it on his canvas just as he sees it, having previously selected the best point of view, and marked for omission or improvement what is not beautiful, or what would interfere with the effect of his picture as a work of high art. His first step, therefore, is to fix upon the size of his canvas, or the distance at which the picture is to be seen, which determines its size. His own eye is a camera obscura, and the relation between the picture or image on its retina is such, that if we could view it from the centre of curvature of the retina, (the centre of visible direction,) a distance of half an inch, it would have precisely the same apparent magnitude as the object of which it is the image. Let us now suppose that the artist wishes to avail himself of the picture in the camera obscura as received either on paper or ground glass, or of a photograph of the scene he is to paint. He must make use of a camera whose focal length is equal to the distance at which his picture is to be seen, and when the picture thus taken is viewed at this distance (suppose two feet) it will, as a whole, and in all its parts, have the same apparent magnitude as the original object. This will be understood from Fig. 47, in which we may suppose H to be the lens of the camera, RB the object, and Hy' the distance at which it is to be viewed. The size of the picture taken with a lens at H, whose focal length is Hy, will be b'r, and an eye placed at H will see the picture b'r under an angle b'H', equal to the angle RHB, under which the real object RB was seen by the artist from н. In like manner, a larger picture, byr, taken by a camera the focal distance of whose lens at H is Hy, will be an accurate representation of the object RB, when viewed from H, and of

the same apparent magnitude. If either of these pictures, b'r or br, are viewed from greater or less distances than Hy, or нy, they will not be correct representations of the

object RB, either in apparent magnitude or form. That they will be of a different apparent magnitude, greater when viewed at less distances than нy', Hу, and less when viewed at greater distances, is too obvious to require any illustration. That they will differ in form, or in the relative apparent size of their parts, has, so far as I know, not been conjectured. In order to shew this, let us suppose a man six feet high to occupy the foreground, and another of the same size to be placed in the middle distance, the distance of the two from the artist being ten and twenty feet. The apparent magnitudes of these two men on the photograph will be as two to one; and if we look at it at any distance greater or less than the focal length Hy' of the lens, the same proportion of two to one will be preserved, whereas if we look at the original figures at a greater or less distance from them than the place of the artist, the

ratio of their apparent magnitudes will be altered. If the artist, for example, advances five feet, the nearest man will be five feet distant and the other fifteen feet, so that their apparent magnitude will now be as three to one.

The same observations apply to a portrait of the human face. In looking at a human profile let us suppose the breadth of the nose to be one inch, that of the ear one inch, and that we view this profile at the distance of three feet from the ear, which is two inches nearer the observer than the nose. The apparent magnitude of the ear and nose will be as thirty-eight to thirty-six inches, whereas if we view the profile from the distance of one foot the ratio will be as fourteen to twelve, that is, the ear will be increased in apparent size more than the nose. Hence it follows that all pictures should be viewed under the same angle of apparent magnitude under which they were seen by the artist as taken photographically, for if we view them at a greater or less angle than this we do not see the same picture as when we looked at the original landscape or portrait, under the same angle of apparent magnitude.

From the observations made in the preceding Chapter on photographic and stereoscopic portraiture, the reader must have already drawn the inference that the same landscape or building, seen at different distances, varies essentially in its character,-beauties disclosing themselves and defects disappearing as we approach or recede from them. The picture in the camera, therefore, as used by Mr. Thomson, or, what is still better, with the exception of colour, the photograph obtained by the same instrument, will supply the artist with all the general materials for his picture.

The photograph will differ considerably from any

sketch which the artist may have himself made, owing to certain optical illusions to which his eye is subject. The hills and other vertical lines in the distance will be lower in the photograph than in his sketch.1 The vertical lines of buildings will converge upwards in the photograph, as they ought to do, in receding from the eye; and in the same picture there will be a confusion, as we shall afterwards shew, in the delineation of near and minute objects in the foreground, increasing with the size of the lens which he has employed.

In his admirable chapter "On Finish," Mr. Ruskin has established, beyond a doubt, the most important principle in the art of painting. "The finishing of nature," he states, "consists not in the smoothing of surface, but the filling of space, and the multiplication of life and thought;" and hence he draws the conclusion, that "finishing means, in art, simply telling more truth." Titian, Tintoret, Bellini, and Veronese have, as he has shewn, wrought upon this principle, delineating vein by vein in the leaf of the vine, petal by petal in the borage-blossoms, the very snail-shells on the ground, the stripe of black bark in the birch-tree, and the clusters of the ivy-leaved toad-flax in the rents of their walls; and we have seen that a modern artist, Delaroche, considers a finish of inconceivable minuteness as

1 Sir Francis Chantrey, the celebrated sculptor, shewed me, many years ago, a Sketch-Book, containing numerous drawings which he had made with the Camera Lucida, while travelling from London to Edinburgh by the Lakes. He pointed out to me the flatness, or rather lowness, of hills, which to his own eye appeared much higher, but which, notwithstanding, gave to him the idea of a greater elevation. In order to put this opinion to the test of experiment, I had drawings made by a skilful artist of the three Eildon hills opposite my residence on the Tweed, and was surprised to obtain, by comparing them with their true perspective outlines, a striking confirmation of the observation made by Sir Francis Chantrey.