There are two kinds of perspective, linear and aËrial. The former has to do with the manner in which horizontal lines appear to converge as they recede from the foreground, and so produce the effect of distance. The latter has to do with the effect of distance, which is due to the successive gradations of gray in color noticeable in objects farther and farther away from the observer.

AËrial Perspective.—To the student, aËrial is color perspective, because of the modifications which colors undergo when removed to a distance. Modifications of tone are largely due to varying distance, and so aËrial perspective is largely a matter of values. That they are due to the greater or less thickness of the atmosphere is only a matter of interest, not of importance, to the artist; the important thing to him is that the careful study of values is necessary to relief, perspective, and particularly, atmosphere and envelopment in a picture.

To the student, aËrial perspective should be only a matter of observation and of the study of relations of color and value. There are no rules. The effect depends on greater or less density of atmosphere. Near objects are seen through a thin stratum of air, and farther objects through a thicker one. All you have to do to express it is to recognize the relative tones of color. Paint the colors as they are, as you see them in nature, and you need have no trouble with aËrial perspective.

But though I say "this is all you have to do," don't imagine that I mean that it is always easy, or that it can be done without thought and study. You will have to use all your powers of perception if you wish to do good work in this direction. Especially on clear days, or in those climates where the air is so rare that objects at great distances seem near, you will find that atmospheric perspective is simply another name for close values. And close values, you remember, are the most subtle of relations of light and shade and color.

The only rule for aËrial perspective is to use your eyes, and do nothing without a previous careful study of nature.

Linear Perspective.—For most kinds of painting, a technical knowledge of linear perspective is not necessary, although every painter should understand the general principles of it. In most cases all the exactness needed can be obtained by comparing all lines carefully with the pencil or brush handle held horizontally or vertically, and studying the angle any line makes with it. Apply to all objects in perspective the same observation that you do in any other kind of drawing, and you will have little trouble, as long as you are drawing from an object before you. But if you go into perspective at all, go into it thoroughly. A little perspective is a dangerous thing, and more likely to mix you up by suggesting all sorts of half-understood things than to be of any real help.

There are some kinds of subjects, however, which require a complete knowledge of all the rules and processes of perspective. Whenever you have to construct a picture from details stated but not seen; when you have a complicated architectural interior or exterior; when figures are to be placed at certain distances or in definite positions, and they are too numerous or the conditions are otherwise such that you cannot pose your models for this purpose; then you may have to make most elaborate perspective plans, and lay out your picture with great exactness, or the drawing which is fundamental to such a picture will not be true.

Such men as GÉrÔme and Alma-Tadema plan their pictures most carefully, and so did Paul Veronese, and it requires a thorough and practical knowledge of perspective. But this is not the place to teach you perspective. It is a subject which requires special study, and whole volumes are given to the elucidation of it. In a work of this kind anything more than a mention of the bearings of perspective on painting would be out of place. If you do not care to take up seriously the study of perspective, avoid attempting to paint any subjects which call for it; or, if you do care to study it, get a special work on that subject, give plenty of time to it, and study it thoroughly.

Foreshortening.—In this connection I may speak of something which is akin to perspective, yet the very reverse of it. As its name implies, foreshortening means the way in which anything seems shortened or in modified drawing as it projects towards you; while perspective is the manner in which lines appear as they recede from you. Like aËrial perspective, the best way to study foreshortening is to study nature, not rules.

Perspective can be worked out by rule, foreshortening cannot. Pose your model, or if it be a branch of a tree, or anything of that sort, place yourself in the proper position with reference to it, and then study the drawing as it appears, thinking nothing of how it is; make your measurements, and place your lines as if there were no problem of foreshortening at all, but study the relations of lines, of size, and of values, and the foreshortening will take care of itself.

After all, foreshortening is only good drawing, and a good draughtsman will foreshorten well, while a bad draughtsman will not. Therefore, learn to draw, and don't worry about the foreshortening.