AT the revival of the arts, some evil genius, who was determined to retard the progress of painting, dictated this rule. “A picture should always have its horizon the height of the eye that looks at it—in nature, the eye being always the height of the horizon; therefore a picture will be most like nature that has its horizon the height of the natural eye.” One of the falsest rules that ever was founded on a false principle! and this is the more lamentable, as it has spoiled, in point of perspective, three parts of the historical pictures that have ever been painted.
As it is very difficult to destroy a rooted error, and as this is a most pernicious one, it is necessary to be full and particular.
When I say eye and horizon—the natural eye and horizon are meant. When the terms artificial eye and artificial horizon are used, the eye and the horizon represented in painting are to be understood. We must be clear in this distinction, for it is the confounding of the ideas expressed by these terms which has occasioned the mischief.
The eye, and the horizon, are always of the same height—therefore
The artificial eye and the artificial horizon must always be so—but
There is no connection between the real eye, and the artificial horizon.
In every picture the artificial eye, or point of sight, is supposed to be at a certain height from the base-line; as high as a human figure would be, represented as standing there. To this point every thing in the picture tends, as every thing in a real view tends to the natural eye. The picture then, as far as this circumstance is concerned, is perfect, if the artificial eye and the artificial horizon go together; for these always bear the same relation to each other, let the picture be placed any where.
Let A be the eye, B the picture (in section) and c the horizon of the picture.—The eye is always the apex of the cone; there is constantly the same relation between the parts in every position. It must be observed that there is a defect in this illustration which it was impossible to avoid—for tho’ I have considered A as the eye, yet upon paper, it is artificial as well as the picture B. If you cannot make this distinction, I propose the following demonstration.——Take a landscape and stand it upon a table—hang it up the height of the eye—above the height—put it upon a chair—upon the floor—it still, perspectively considered, is seen equally well—for
The real eye is always the height of the artificial eye, whether the picture be fixed in the cieling or laid upon the floor.