The Washington herald., 1915-12-26

Illustration No. Showing the sf.
feet of simultaneous contrast The
VS. are of equal brightness.
denly removed without disturbing the hxa-
ton in its place will be seen a red spot
more luminous than the surroundings and
Of more saturated reddish appearance.
Successive contrasts further complicats
the appearance of colors. After stimulat-
ing the eye with red light, IL the eye is
suddenly fixed upon green color the lat
ter will appear more intense or saturated
in color for a moment than IL the eyes had
not been previously stimulated by red
light. On alternating these colors by
means Of a rotating disk at low speed very
brilliant effects are seen.
Such successive contrasts are Of i'm
portance in the study and application Of
color science. For instance In permitting
the eye to rove over painting or bril-
liantly colored rug the appearance Of the
various individual colors is Influenced By
the previous retinal stimulation.
Simultaneous contrast is another -
ceedngly interesting subject simui
taneous contrast. for example, takes place
when on viewing a gray pattern on a dark
ooShSiouhu IL oppCoIS UTlSuteT Iu6u Nu00
viewed upon a light background. Illustra-
ton No. was originally made by cutting
the two figures In the form Of from the
same gray paper. On placing them 40
shown. one on black and one on q white
background, the one on a white ground
appears darker than the other The effect
is so persistent that a much darker cray
can be placed upon the black BACKGROUND
and yet 1t will appear brighter than the
fha xx-hft l. A. a. l.
practically impossible to make both ap-
pear alike by decreasing the brightness Of
the gray on the dark ground.
II several gray papers Of different
shades be placed edge to edge In an order
that goes from dark to light or from light
to dark the edge Of a lighter gray strip
that is adjacent to a darker one will ap-
pear brighter than the other edge Of the
lighter gray strip. Such a specimen can
be obtained by exposing a Photographic
plate in a very weak light by pulling out
the slide Of the plate holder a half inch
at a time at regular intervals
striking demonstration Of brightness
contrast can be performed by viewing a
gray paper through q hoe in a white unil-
Illuminated screen. 1t appears very bright
in contrast to the dark surrounding. On
Illuminating the white surroundings 1t Is
possible to make the former bright spot
When two colors such as red and green
are juxtaposed they are accentuated in
saturation and appear deeper In hue. In
the case of these two colors they appear
to move further apart in hue. When the
two colors are separated the contrast
effect practically disappears. II disk of
green be placed upon larger disk Of red
the contrast is very effective but if the
smaller disk is outlined by a black circle
A. l.,
placed upon a green background the gray
figure will appear Of pink hue. The con-
trast hue produced in this manner is ap-
proximately, though in general not exactly.
Complementary to the exciting color.
Colored shadows were noticed by such =
great colorist as Leonardo da Vinci.
These are illustrated by casting the
shadow Of q pencil on white paper BY
light entering the window. Only black
and white contrast is seen. However. IL
from another direction light from an in
candescent lamp is permitted to fall on the
paper another shadow is produced. n
the two shadows are approximately Of
the same brightness the contrast colors
Of the shadows are very striking.
The white ground on the outside Of the
shadows is receiving the mixed light from
the two illupinants while the shadow cast
By daylight receives light from only the
lnC4nQeSCont lamp ana appears yellow.
The other shadow receiving only daylight
appears blue. Shadows in a landscape ap-
pear blue because they receive light from
the sky and they often appear more vivid
owing to the contrast effects.
Irradiation Is the name that is given to
the phenomenon of the apparent increase
In size Of objects as they are increased in
brightness. The crescent Of the new moon
appears larger than the remainder Of the
disc. A filament Of an incandescent lamp
appears to increase in diameter as its
temperature is raised from a dull red to
its normal operating temperature.
Some scientists say that this is due to
the spreading of the image In the retina
Of the eye on account Of a stimulation Of
nerves outside its actual geometric bound
ary. Others say that 1t is due to aberra-
tons in the optical system of the eye.
In Illustration No. 2 the inner white
square appears larger than the inner black
square under high Illumination, yet both
are identical in size The phenomenon of
simultaneous brightness contrast IL also
evident. the white square amid black sur.
roundings appearing brighter than the
larger white square. Such effects are also
perceptible with colored objects.