painters gained color at the expense of light and therefore lowered the
scale of color in their representations of nature. It is interesting to
see how increasing knowledge, as centuries passed, directed painters as it
did others onward toward the truth. Turner was one of the first to abandon
the older methods in an attempt to raise the scale of his paintings toward
a brilliance more resembling nature. By doing this he was able to put
color in shadows as well as in lights. Gradually paintings became more
brilliant. Monet, Claude, and others worked toward this goal until the
brightnesses of paintings reached the limits of pigments. The
impressionists, in their desire to paint nature's light, introduced
something which was nothing more nor less than science. All this time the
true creative artist was introducing science--in fact, illusions--to
produce the perfect illusion which was his goal. A survey of any
representative paintings' gallery shows the result of the application of
more and more knowledge, as the art of painting progressed through the
centuries. Surely we cannot go back to the brown shadows and sombre
landscapes of the past.
In the earliest art, in the efforts of children, in the wall-paintings of
the Egyptians, and in Japanese representation of nature, the process is
selective and not imitative. Certain things are chosen and everything else
is discarded. In such art selection is carried to the extreme. Much of
this simplicity was due to a lack of knowledge. Light and shade, or
shading, was not introduced until science discovered and organized its
facts. Quite in the same manner linear and aerial perspective made their
appearances until in our present art the process of selection is complex.
In our paintings of today objects are modeled by light and shade; they are
related by perspective; backgrounds and surroundings are carefully
considered; the proper emphasis of light, shade and color are given to
certain details. The present complexity provides unprecedented
opportunities for the application of knowledge pertaining to illusions but
it should be understood that this application tends only toward realism of
external things. Idealism in art and realism of character and expression
are accomplished by the same tools--pigments and brushes--as realism of
objective details is attained and there is nothing mysterious in the
masterpieces of this kind. Mystery in art as in other activities is merely
lack of understanding due to inadequate knowledge. Mysteries of today
become facts tomorrow. Science moves with certainty into the unknown,
reaping and binding the facts and dropping them behind where they may be
utilized by those who will.
The painter can imitate aerial perspective although many centuries elapsed
before mankind was keen enough to note its presence in nature. The
atmospheric haze diminishes the brightness of very bright objects and
increases that of dark objects. It blurs the distant details and adds a
tinge of blue or violet to the distance. In painting it is a powerful
illusion which the painter has learned to employ.
The painter can accurately imitate mathematical or linear perspective but
the art of early centuries does not exhibit this feature. In a painting a
tremendously powerful illusion of the third dimension is obtained by
diminishing the size of objects as they are represented in the distance.
Converging lines and the other manifold details of perspective are aiding
the artist in his efforts toward the production of the great illusion of
painting.
The painter cannot imitate focal perspective or binocular perspective. He
can try to imitate the definition in the central portion of the visual
field and the increased blurring toward the periphery. Focal perspective
is not of much importance in painting, because it is scarcely perceptible
at the distances at which paintings are usually viewed. However the
absence of binocular perspective in painting does decrease the
effectiveness of the illusion very markedly. For this reason a painting is
a more successful illusion when viewed with one eye than with two eyes. Of
course, in one of nature's scenes the converse is true because when
viewing it with both eyes all the forms of perspective cooeperate to the
final end--the true impression of three dimensions.
The painter may imitate the light and shade of solid forms and thereby
apparently model them. In this respect a remarkable illusion of solid form
or of depth may be obtained. For example, a painted column may be made to
appear circular in cross-section or a circle when properly shaded will
appear to be a sphere. Both of these, of course, are pure illusions. Some
stage paintings are remarkable illusions of depth, and their success
depends chiefly upon linear perspective and shadows. However, the illusion
which was so complete at a distance quite disappears at close range.
The inadequate range of brightnesses or values obtainable by means of
pigments has already been discussed. The sky in a landscape may be
thousands of times brighter than a deep shadow or a hole in the ground. A
cumulus cloud in the sky may be a hundred thousand times brighter than the
deepest shadow. However, the artist must represent a landscape by means of
a palette whose white is only about thirty times brighter than its black.
If the sun is considered we may have in a landscape a range of brightness
represented by millions.
This illustrates the pitiable weakness of pigments alone as
representative media. Will not light _transmitted_ through media some day
be utilized to overcome this inherent handicap of reflecting media? To
what extent is the success of stained glass windows due to a lessening of
this handicap? The range of brightness in this case may be represented by
a black (non-transmitting) portion to the brightness of the background
(artificial or sky) as seen through an area of clear glass. Transparencies
have an inherent advantage over ordinary paintings in this respect and
many effective results may be obtained with them even in photography.
It is interesting to study the effect of greatly increasing the range of
values or brightnesses in paintings by utilizing non-uniform distributions
of light. Let us take a given landscape painting. If a light-source be so
placed that it is close to the brighter areas (perhaps clouds and sky near
the sun) it will illuminate this brighter portion several times more
intensely than the more distant darker portions of the picture (foreground
of trees, underbrush, deep shadows, etc.). The addition to the
effectiveness of the illusion is quite perceptible. This effect of
non-uniform lighting may be carried to the extreme for a painting by
making a positive lantern-slide (rather contrasty) of the painting and
projecting this slide upon the painting in accurate superposition. Now if
the painting is illuminated solely by the "lantern-slide" the range of
contrast or brightness will be enormously increased. The lightest portions
of the picture will now be illuminated by light passing through the almost
totally transparent portions of the slide and the darkest portions by
light greatly reduced by passing through the nearly opaque portions of the
slide. The original range of contrast in the painting, perhaps twenty to
one, is now increased perhaps to more than a thousand to one. This
demonstration will be surprising to anyone and will emphasize a very
important point to the painter.
The painter has at his disposal all the scientific facts of light, color,
and vision. Many of these have been presented elsewhere,[9] and those
pertaining to illusions have been discussed in preceding chapters. These
need not be repeated here excepting a few for the purpose of reminding the
reader of the wealth of material available to the painter and decorator.
Many tricks may be interjected into the foreground for their effect upon
the background and vice versa. For example, a branch of a tree drooping in
the foreground apparently close to the observer, if done well, will give a
remarkable depth to a painting. Modeling of form may be effected to some
extent by a judicious use of the "retiring" and "advancing" colors. This
is one way to obtain the illusion of depth.
After-images play many subtle parts in painting. For example, in a
painting where a gray-blue sky meets the horizon of a blue-green body of
water, the involuntary eye-movements may produce a pinkish line just above
the horizon. This is the after-image of the blue-green water creeping
upward by eye-movements. Many vivid illusions of this character may be
deliberately obtained by the artist. Some of the peculiar restless effects
obtained in impressionistic painting (stippling of small areas with
relatively pure hues) are due to contrasts and after-images.
A painting came to the author's notice in which several after-images of
the sun, besides the image of the sun itself, were disposed in various
positions. Their colors varied in the same manner as the after-image of
the sun. Doubtless the painter strove to give the impression which one has
on gazing at the sun. Whether or not this attempt was successful does not
matter but it was gratifying to see the attempt made.
There are many interesting effects obtainable by judicious
experimentation. For example, if a gray medium be sprayed upon a landscape
in such a manner that the material dries in a very rough or diffusing
surface some remarkable effects of fog and haze may be produced. While
experimenting in this manner a very finely etched clear glass was placed
over a landscape and the combined effect of diffusely reflected light and
of the slight blurring was remarkable. By separating the etched glass from
the painting a slight distance, a very good imitation "porcelain" was
produced. The optical properties of varnishes vary and their effect varies
considerably, depending upon the mode of application. These and many other
details are available to the painter and decorator. An interesting example
among many is a cellulose lacquer dyed with an ordinary yellow dye. The
solution appears yellow by transmitted light or it will color a surface
yellow. By spraying this solution on a metallic object such as a
nickel-plated piece, in a manner that leaves the medium rough or
diffusing, the effect is no longer merely a yellow but a remarkable lustre
resembling gilt. Quite in the same manner many effects of richness, depth
of color, haziness, etc., are obtainable by the artist who is striving to
produce a great illusion.
All the means for success which the painter possesses are also available
to the decorator; however, the latter may utilize some of the illusions of
line, form, irradiation, etc., which the architect encounters. The
decorator's field may be considered to include almost all of the painter's
and much of the architect's. This being the case, little space will be
given to this phase of the subject because painting and architecture are
separately treated. The decorator should begin to realize more fully the
great potentiality of lighting in creating moods or in giving expression
to an interior. The psychology of light and the use of lighting as a mode
of expression have barely been drawn upon by the decorator. Lighting has
already been discussed so it will be passed by at this point.
The practice of hanging pictures on walls which are brilliantly colored is
open to criticism. There are galleries in existence where paintings are
hung on brilliant green or rose walls. The changes in the appearance of
the object due to these highly colored environments are easily
demonstrated by viewing a piece of white paper pinned upon the wall. On
the green wall, the white paper appears pinkish; on the rose wall, it
appears bluish or greenish. A portrait or a picture in which there are
areas of white or delicate tints is subject to considerable distortions in
the appearance of its colors. Similarly, if a woman must have a colored
background, it is well to choose one which will induce the more desirable
tints in her appearance. The designer of gowns certainly must recognize
these illusions of color which may be desirable or undesirable.
The lighting of a picture has already been mentioned, but the discussion
was confined solely to distribution of light. The quality of the light
(its spectral character) may have an enormous influence upon the painting.
In fact with the same painting many illusions may be produced by lighting.
In general, paintings are painted in daylight and they are not the same in
appearance under ordinary artificial light. For this reason the artist is
usually entitled to the preservation of the illusion as he completed it.
By using artificial daylight which has been available for some years, the
painting appears as the artist gave it his last touch. Of course, it is
quite legitimate to vary the quality of light in case the owner desires to
do so, but the purpose here is to emphasize the fact that the quality of
light is a powerful influence upon the appearance of the painting. The
influence is not generally enough recognized and its magnitude is
appreciated by relatively few persons.
All other considerations aside, a painting is best hung upon a colorless
background and black velvet for this purpose yields remarkable results.
Gray velvet is better, when the appearance of the room is taken into
consideration, as it must be. However, the influence of dark surroundings
toward enhancing the illusion is well worth recognizing. In the case of a
special picture or a special occasion, a painting may be exhibited in a
booth--a huge shadow-box not unlike a show-window in which the
light-sources are concealed. Such experiments yield many interesting data
pertaining to the illusions which the painter strives to obtain.
[Illustration: Fig. 82.--Illustrating the apparent distortion of a picture
frame in which the grain of the wood is visible.]
Incidentally on viewing some picture frames in which the grain of the wood
was noticeable, the frames did not appear to be strictly rectangular. The
illusions were so strong that only by measuring the frames could one be
convinced that they were truly rectangular and possessed straight sides.
Two of these are represented in Figs. 82 and 83. In the former, the
horizontal sides appear bent upward in the middle and the two vertical
sides appear bowed toward the right. In Fig. 83, the frame appears
considerably narrower at the left end than at the right. Both these frames
were represented in the original drawings by true rectangles.
Many illusions are to be seen in furniture and in other woodwork in which
the grain is conspicuous. This appears to the author to be an objection in
general to this kind of finish. In Fig. 84 there is reproduced a
photograph of the end of a board which was plane or straight
notwithstanding its warped, or bowed, appearance. The original photographs
were placed so as to be related as shown in the figure. Various degrees of
the illusion are evident. The reader will perhaps find it necessary to
convince himself of the straightness of the horizontal edges by applying a
straight edge. These are examples of the same illusion as shown in Figs.
37 to 40.
[Illustration: Fig. 83.--Another example similar to Fig. 82.]
[Illustration: Fig. 84.--From actual photographs of the end-grain of a
board.]
Perhaps a brief statement regarding the modern _isms_ in art may be of
interest. In considering some of the extreme examples, we must revise our
idea that art is or should be always beautiful. The many definitions of
art would lead us too far afield to discuss them here but in its most
extended and popular sense, art may be considered to mean everything
which we distinguish from nature. Certainly art need not be beautiful,
although it does seem that the world would welcome the beautiful and would
get along contentedly without art that is ugly or repulsive. The modern
_isms_ must be viewed with consideration, for there are many impostors
concealing their inabilities by flocking to these less understood fields.
However, there are many sincere workers--research artists--in the modern
_isms_ and their works may best be described at present as experiments in
the psychology of light, shade, and color. They have cast aside or reduced
in importance some of the more familiar components such as realism and are
striving more deeply to utilize the psychology of light and color. Some of
them admit that they strive to paint through child's eyes and mind--free
from experience, prejudice, and imitation. These need all the scientific
knowledge which is available--and maybe more.
In closing this chapter, it appears necessary to remind the artist and
others that it is far from the author's intention to subordinate the
artist's sensibility to the scientific facts or tools. Art cannot be
manufactured by means of formulae. This would not be true if we knew a
great deal more than we do pertaining to the science of light, color, and
vision. The artist's fine sensibility will always be the dominating
necessity in the production of art. He must possess the ability to compose
exquisitely; he must be able to look at nature through a special
temperament; he must be gifted in eye and in hand; he must be master of
unusual visual and intellectual processes. But knowledge will aid him as
well as those in other activities. A superior acquaintance with scientific
facts lifted past masters above their fellows and what helped Leonardo da
Vinci, Rembrandt, Velasquez, Turner, Claude, Monet, and other masters will
help artists of today. What would not those past masters have accomplished
if they had available in their time the greater knowledge of the present!
XIII
ARCHITECTURE
Many illusions are found in architecture and, strangely enough, many of
these were recognized long before painting developed beyond its primitive
stages. The architecture of classic Greece displays a highly developed
knowledge of many geometrical illusions and the architects of those
far-off centuries carefully worked out details for counteracting them.
Drawings reveal many illusions to the architect, but many are not
predicted by them. The ever-changing relations of lines and forms in
architecture as we vary our viewpoint introduce many illusions which may
appear and disappear. No view of a group of buildings or of the components
of a single structure can be free from optical illusions. We never see in
the reality the same relations of lines, forms, colors, and brightnesses
as indicated by the drawings or blue-prints. Perhaps this is one of the
best reasons for justifying the construction of expensive models of our
more pretentious structures.
No detailed account of the many architectural illusions will be attempted,
for it is easy for the reader to see many of the possibilities suggested
by preceding chapters. However, a few will be touched upon to reveal the
magnitude of the illusory effect and to aid the observer in looking for
or recognizing them, or purely for historical interest. In architecture
the eye cannot be wholly satisfied by such tools as the level, the square,
and the plumb-line. The eye is satisfied only when the _appearance_ is
satisfactory. For the purpose of showing the extent of certain
architectural illusions, the compensatory measures applied by the Greeks
are excellent examples. These also reveal the remarkable application of
science to architecture as compared with the scanty application in
painting of the same period.
During the best period of Grecian art many refinements were applied in
order to correct optical illusions. It would be interesting to know to
what extent the magnitude of the illusions as they appeared to many
persons were actually studied. The Parthenon of Athens affords an
excellent example of the magnitude of the corrections which the designer
thought necessary in order to satisfy the eye. The long lines of the
architrave--the beam which surmounts the columns or extends from column to
column--would appear to sag if it were actually straight. This is also
true of the stylobate, or substructure of a colonnade, and of pediments
and other features. These lines were often convex instead of being
straight as the eye desires to see them.
In the Parthenon, the stylobate has an upward curvature of more than four
inches on the sides of the edifice and of more than two and a half inches
on the east and west fronts. Vertical features were made to incline inward
in order to correct the common appearance of leaning outward at the top.
In the Parthenon, the axes of the columns are not vertical, but they are
inclined inward nearly three inches. They are said also to be inclined
toward each other to such a degree that they would meet at an altitude of
one mile above the ground. The eleven-foot frieze and architrave is
inclined inward about one and one-half inches.
In Fig. 85, _a_ represents the front of a temple as it should appear; _b_
represents its appearance (exaggerated) if it were actually built like _a_
without compensations for optical illusions; _c_ represents it as built
and showing the physical corrections (exaggerated) in order that it may
appear to the eye as _a_ does.
Tall columns if they are actually straight are likely to appear somewhat
shrunken in the middle; therefore they are sometimes made slightly swollen
in order to appear straight. This outward curvature of the profile is
termed an entasis and in the Parthenon column, which is thirty-four feet
in height, amounted to about three-fourths of an inch. In some early
Grecian works, it is said that this correction was overdone but that its
omission entirely is quite unsatisfactory. Some authorities appear to
believe that an excellent compromise is found in the Parthenon columns.
[Illustration: Fig. 85.--Exaggerated illusions in architecture.]
One of the conditions which is responsible for certain illusions and has
been compensated for on occasions is represented in Fig. 86. On the left
are a series of squares of equal size placed in a vertical row. If these
are large so that they might represent stories in a building they will
appear to decrease in size from the bottom upward, because of the
decreasing projection at the eye. This is obvious if the eye is
considered to be at the point where the inclined lines meet. In order to
compensate for the variation in visual angle, there must be a series of
rectangles increasing considerably in height toward the top. The
correction is shown in the illustration. It is stated that an inscription
on an ancient temple was written in letters arranged vertically, and in
order to make them appear of equal size they were actually increased in
size toward the top according to the law represented in Fig. 86. Obviously
a given correction would be correct only for one distance in a given
plane.
[Illustration: Fig. 86.--Illustrating the influence of visual angle upon
apparent vertical height.]
In Chapter VIII the phenomenon of irradiation was discussed and various
examples were presented. It exerts its influence in the arts as elsewhere.
Columns viewed against a background of white sky appear of smaller
diameter than when they are viewed against a dark background. This is
illustrated in Fig. 87 where the white and the black columns are supposed
to be equal in diameter.
The careful observer will find numberless optical illusions and
occasionally he will recognize an attempt on the part of the architect to
apply an illusory effect to his advantage. In Fig. 88 some commonplace
illusions are presented, not for what they are worth, but to suggest how
prevalent they may be. Where the pole or column intersects the arches or
circle, there is an apparent change in the direction of the curved lines.
The different types of arches show different degrees of the illusion. It
may be of interest for the reader to refer to preceding chapters and to
ascertain what types of illusions are involved.
[Illustration: Fig. 87.--Irradiation in architecture.]
If a high wall ends in a series of long horizontal steps at a slightly
inclined sidewalk, the steps are not likely to appear horizontal.
Some remarkable illusions of depth or of solid form are given to flat
surfaces when snow is driven against them so as to adhere in decreasing
amounts similar to shading.