The greatest value in the illusion of relief lies in its assistance to recognition, for with the forms rounded by shading and separated with the appearance of relief which they have in nature, details of the work are less likely to complicate the design to the eye, than if the flat surface of the canvas be emphasized by the avoidance of relief. For the eye has to be considered before the mind, and it is of immense importance that the brain should have the least possible work to do in assisting the eye to interpret a thing of art. It would appear then that the minimum extent to which relief should be given in a painting is that point below which the things painted do not seem to have their three dimensions indicated. Beyond this the painter is at liberty to proceed as he pleases. Some great artists, notably Lionardo, were inclined to think that it is impossible to give too much relief to a figure, and this may be so theoretically, but practically there is a line to be drawn because life is limited, and after a certain point is reached, the work of shading for relief is so tedious an operation, that half a lifetime would be required to execute a picture of three or four figures if the artist wished to produce the strongest illusion in his power to give. A Russian artist of high merit who essayed the task, spent an average time of five years in ceaseless toil on each figure he completed, and even then frequently remarked that he had not given to his figures the full relief he desired to exhibit. It is well known that Lionardo gave long and close attention to this matter in his pictures, and he produced some extraordinary examples of relief, of which the finest is, perhaps, the Litta Madonna,[a] but one cannot help regretting that he did not rest satisfied with a lower point of excellence in respect of the illusion, so that he could spend more time in general design.

Apart from the relief given by shading in painting, there is an important mechanical method of improving the illusion, though this can only be occasionally adopted. The figures in any well painted picture will appear to stand out in high relief if we lose sight of the frame and other surroundings which distinctly inform us that the work is a flat surface. This is why a painting invariably seems to improve if seen through a tube of such diameter that the frame is excluded from the vision. Advantage of this fact has been many times taken in the exhibition of single pictures, when, by the exclusion of the frame, the concealment of the edges of the work by curtain arrangements, and the concentration of all the available light upon the canvas, such perfect relief has been obtained that observers have been sometimes unable to distinguish the art from the life. It was the effect of the surroundings of a picture upon the sight, that led to a practice in design resulting in the exclusion of these surroundings to some extent when the eye is directed towards the centre of the work where the principal figure is commonly stationed. This practice is to avoid accessories as far as possible near the figure, and to provide considerable open space above it, and also at the sides when the composition allows, so that the observing eye has not of necessity to range close to the frame of the picture. In a good design of this kind the central figure or figures come out in strong relief, the attraction of the work being consequently much enhanced. Obviously the painted figures should be of life size, or nearly so, for the illusion of relief to be strikingly marked, and the conditions necessarily prevent the adoption of the scheme in a design of many figures. It is most successful with a single figure, and has been carried out with two figures, but never with more than two except in a few pictures of great size.

The number of artists who have taken advantage of this mechanical device is not large, but it includes some of the first masters. The plan may be used in both exterior and interior scenes. In the former the figures must be thrown against the sky, and it is a distinct advantage if there be no trees or other objects on either side of the figures, which also stand out above the horizon, though this is immaterial if the figure be set in a confined space, as an arch, or between the columns of a loggia, and the foliage is not seen through this space.

The most famous pictures where the scheme is used in exterior work are amongst the finest portraits known to us, namely, Lionardo's Mona Lisa, and Raphael's Maddalena Doni and Angelo Doni.[b] In 1504 or thereabouts, Lionardo painted a portrait of Mona Lisa sitting in a loggia, the wall of which reached to a third of the height of the canvas.[c] On the wall at each side of the design is a column divided down the centre by the edge of the canvas. There is a landscape setting, in which the middle distance is hidden by rising ground, and only part of the head appears above the horizon. In 1505 Raphael made a study from this picture in which he retained the columns, but raised the wall, and threw the whole head of the figure against the sky. He used this study for the portrait of Maddalena Doni, but in this he still further improved the design by removing the columns, and extending to the shoulders that part of the figure above the horizon, the line of which divides the picture in equal halves, instead of being drawn at two thirds of the height as in the first Mona Lisa. When Lionardo executed the Louvre portrait of this lady, he removed the columns, but slightly reduced the portion of the head seen against the sky. Raphael's plan, which was also used in the portrait of Angelo Doni, is obviously far superior to that in the Mona Lisa design, for the relief is necessarily better marked. The scheme was not new to Raphael at the time, except in portraiture, for it is exhibited in three of his very early sacred works.[d]

One of the best examples in existence of this method of securing relief is Tintoretto's Presentation of the Virgin.[e] On the right of the picture is a wide flight of stairs, curving round as they ascend. The Virgin is moving up these steps in advance of some attendants, and the curved stairway enables all the figures to stand out in fine relief against the sky. If well managed some considerable space above the figures is sufficient for the illusion even if the sides are partly closed, as in Albertinelli's beautiful Salutation.[f] Where only a small portion of the figure can be shown above the horizon, the use of a faint far distance helps in the scheme of relief. Thus, in Marco Basaiti's Christ on the Mount of Olives,[g] where Christ stands on the top of a rock which hides the middle distance, His head only is above the horizon, but the rest of the figure is thrown against a faint far distance, the relief being excellent. A modification of this plan is observable in Lionardo's Virgin and Child with St. Anne.[h]

So far as the writer has been able to ascertain, the first known painting where a crucifix is thrown against the sky is by Antonella da Messina.[i] The Cross is fixed in the foreground and extends to the top of the picture, being cut half-way up and just below the feet of Christ by the line of the horizon. The relief is very fine. This scheme was imitated with more or less success but never quite so perfectly, till Titian produced his magnificent Cross. Here the Crucifix is cast against a sombre evening sky, with the Virgin and two imploring Saints at the foot.[j] Rubens improved upon this design with several variations. In one he hid the foot of the Cross, though the tops of buildings are seen in the middle distance[k]; and in another, which is still finer, the time of the scene is late evening, and dark vague outlines suggest a landscape. But all these examples are cast into the shade by Van Dyck's Antwerp picture, than which there is certainly no more impressive painted Crucifixion in existence. In this the foot of the Cross is not shown, nor is there any ground to be seen, and the figure stands out against a dark forbidding sky, awful, but sublimely real, as if set in boundless space for all eternity.[l]

There are many variations of the above designs, particularly among the Works of Venetian artists, but those quoted may be regarded as typical. How easy it is to hinder the illusion is seen in Sodoma's Sacrifice of Abraham,[m] where both figures are set against the sky, but trees behind them and at the side destroy the relief, though the foliage is by no means thick. In Girolami da Libri's Madonna and Child with St. Anne, a pomegranate tree interposes[n]; and a curtain falls at the back of a group by Bernadino da Conti,[o] the illusion in both cases being consequently robbed of its effect.

Some of the Dutch artists of the seventeenth century used a clear sky for the purpose of enhancing the relief of their figures, but as these are usually of a comparatively small size, the result is only partially effective. Albert Cuyp and Philip Wouverman painted many pictures with men and animals silhouetted above the horizon, and Paul Potter executed a few of the kind, but of all Dutch painters, Jan Steen secured the best relief with his Terrace Scene.[p] In more recent times the scheme has seldom been adopted for the purpose of relief, but a few Scottish painters practised it in the early nineteenth century. Simson followed Cuyp's plan,[q] and Dyce in a sacred piece equalled the best of the old masters in his manner of producing the illusion.[r] Grant also painted a fine example.[s] Some portrait painters of the English school of the eighteenth century used the scheme in a partial way, but they commonly placed clouds behind the figures thrown against the sky, thus disturbing the illusion.

There is only one method of using this device for assisting in the production of relief in interiors. This is to throw the figure against a high wall which is undecorated or nearly so. The figure must be some little distance in front of the wall, and it is observable that the best effect is obtained when the light throughout the room is equal, but in any case the wall should not have less light than the figure. Inasmuch as the figure has to be of life size or nearly so, to produce the desired result, a very large picture would be necessary for the representation of a standing adult; hence the plan is not attempted with a life-size figure, except with a sitting adult or a standing child. Before this scheme was used for the human figure, that master of relief, M. A. Caravaggio, adopted it for a simple still-life work.[t] A basket of fruit on a plain table, with a high bare wall at the back—the canvas now sombre and darkened, like the soul of the artist, but still remarkable for the relief: this was the first application to interiors of a plan which had been used in exteriors by some of the greatest masters for more than a century.

So far as can be gathered from existing works, thirty or forty years elapsed after the picture of Caravaggio was painted before the scheme was brought into use for the human figure in interiors. In 1630, or thereabouts, Velasquez produced his Christ at the Column.[u] Here the wall is not actually high, but Christ is shown seated on the floor, and hence there is ample wall space over which the eye may rove. It is possible that the adoption of the plan in this instance was the result of accident, but the very unusual pose of Christ hardly warrants the suggestion. Velasquez painted no more pictures of the kind till a quarter of a century later, when he produced Las Meninas. In this the relief is excellent, but it would have been still better without the picture on the wall, and the open door in the background, though the figure seen on the steps through the doorway lends assistance to the illusion.

Towards the middle of the seventeenth century, some followers of the Neapolitan school used the plan occasionally, but the best existing Italian works of the time where it is seen are from the hand of Evaristo Baschenis, a Bergamese monk. He was an excellent painter of still-life, and produced several pictures, each with a boy or a woman seated in the middle of a room near a plain table on which rests a dish of fruit or a gathering of various articles, while at the back there is a high bare wall. In all of these works a fine relief is exhibited, though they are now considerably marred by darkened shadows. A few years later the plan was adopted by some Dutch artists, and later still in France and Germany. Chardin, who in more ways than one seems to have been a French Baschenis, used it in several pictures. In recent times since the study of Velasquez has become a vogue, many artists have successfully followed the plan, and one of the finest examples of it in existence—Lydia Emmet's Patricia[v]—dates as late as 1915.

There are several minor mechanical ways of enhancing relief, most of them providing a setting which acts as a kind of inner frame to the design, the object being to reduce the effect of the actual frame in disturbing the illusion. Portrait painters of the Dutch, Flemish, and English schools, have often placed half length figures in painted ovals on canvas rectangles, and in the case of Hals he sometimes further improved the illusion by extending a hand of the subject over the oval. Hanneman used this oval in a most exceptional way. On a large canvas he painted the bust portraits of Constantine Huygens and his six children, each in a separate oval, the father being in the centre.[w] The scheme is strangely effective, for the attention of the observer is involuntarily confined to one portrait at a time. In genre pictures a doorway may act as the inner frame, but this is only of material value if the picture be of considerable size. The Dutch painters, notably Gerard Dow, loved to paint figures leaning over window-sills, this method usually enhancing the relief, because the eye is apt to be confined for a time to the window-frame. Perhaps the best use of a window for the purpose of relief is Rembrandt's Samson Menacing His Father-in-law, where the old man's head and hands, of life size, are seen protruding from a small window.[x]