Color - Colours
is a visual attribute of
things that results from the light
they emit or absorb or reflect
. The appearance of objects (or light
sources) described in terms of a person's
of their hue and
lightness (or brightness) and saturation. Did you know that the world's
favorite color is blue?
How do colors make you feel
CMYK vs RGB Info-Graph
What is the difference between RGB and CMYK?
is an additive color model in which red, green and blue light are added
together in various ways to reproduce a broad array of colors. The name of
the model comes from the initials of the three additive primary colors,
red, green and blue. The main purpose of the RGB color model is for the
sensing, representation and display of images in electronic systems, such
as televisions and computers, though it has also been used in conventional
photography. Before the electronic age, the RGB color model already had a
solid theory behind it, based in human perception of colors. Additive Color
is color created by mixing a number of different light colors, with shades
of red, green, and blue being the most common primary colors used in
additive color system.
is a subtractive color model, used in color printing, and is also used to
describe the printing process itself. CMYK refers to the four inks used in
some color printing: cyan, magenta, yellow and key (black). Though it
varies by print house, press operator, press manufacturer, and press run,
ink is typically applied in the order of the abbreviation.
explains the mixing of a limited set of dyes, inks,
paint pigments or natural colorants to create a wider range of colors,
each the result of partially or completely subtracting (that is,
absorbing) some wavelengths of light and not others. The color that a
surface displays depends on which parts of the visible spectrum are not
absorbed and therefore remain visible. Subtractive color systems start
with light, presumably white light. Colored inks, paints, or filters
between the watchers and the light source or reflective surface subtract
wavelengths from the light, giving it color. If the incident light is
other than white, our visual mechanisms are able to compensate well, but
not perfectly, often giving a flawed impression of the "true" color of the
surface. Conversely, additive color systems start with darkness. Light
sources of various wavelengths are added in various proportions to produce
a range of colors. Usually, three primary colors are combined to stimulate
humans’ trichromatic color vision, sensed by the three types of cone cells
in the eye, giving an apparently full range.
Matching System is largely a standardized color reproduction system. By
standardizing the colors, different manufacturers in different locations
can all refer to the Pantone system to make sure colors match without
direct contact with one another.
(colors in the light)
is a meteorological phenomenon that is caused by reflection, refraction
and dispersion of light in water droplets resulting in a spectrum of light
appearing in the sky. It takes the form of a multicoloured arc. Rainbows
caused by sunlight always appear in the section of sky directly opposite
the sun. Rainbows can be full circles. However, the observer normally sees
only an arc formed by illuminated droplets above the ground, and centred
on a line from the sun to the observer's eye. In a primary rainbow, the
arc shows red on the outer part and violet on the inner side. This rainbow
is caused by light being refracted when entering a droplet of water, then
reflected inside on the back of the droplet and refracted again when
leaving it. In a double rainbow, a second arc is seen outside the primary
arc, and has the order of its colours reversed, with red on the inner side
of the arc.
World’s Most Visible Color
Nano Meter 555 Midlayer with Motion Capture Markers
is designed to
make you highly visible in any light condition anywhere on earth –
combining insights from experimental psychology, the mechanics of the
human eye and material technology, as well as tapping into the brain’s
pattern recognition system
In daylight, the intense green colour replicates the wavelength of light
that the human eye is most sensitive to. At night, retroreflective
Motion Caption Markers
light up when hit by any passing light source,
creating a pattern that the eye can process as recognisably human in 0.25
(space and object awareness)
is either the number of
used to indicate the color of a single pixel, in a bitmapped
image or video frame buffer, or the number of bits used for each color
component of a single pixel.
a physical point in a raster image, or the smallest addressable element in
an all points addressable display device; so it is the smallest
controllable element of a picture represented on the screen. The address
of a pixel corresponds to its physical coordinates. LCD pixels are
manufactured in a two-dimensional grid, and are often represented using
dots or squares, but CRT pixels correspond to their timing mechanisms.
Each pixel is a sample of an original image; more samples typically
provide more accurate representations of the original. The intensity of
each pixel is variable. In color imaging systems, a color is typically
represented by three or four component intensities such as red, green, and
blue, or cyan, magenta, yellow, and black. In some contexts (such as
descriptions of camera sensors), the term pixel is used to refer to a
single scalar element of a multi-component representation (more precisely
called a photosite in the camera sensor context, although the neologism
sensel is sometimes used to describe the elements of a digital camera's
sensor), while in yet other contexts the term may be used to refer to the
set of component intensities for a spatial position, though this is more
accurately termed a sample. Drawing a distinction between pixels,
photosite and samples avoids confusion when describing color systems that
use chroma subsampling or cameras that use Bayer filter to produce color
components via upsampling. The word pixel is based on a contraction of pix
(from word "pictures", where it is shortened to "pics", and "cs" in "pics"
sounds like "x") and el (for "element"); similar formations with 'el'
include the words voxel, texel and maxel (for magnetic pixel).
is a flat, physical object that has many different color samples present.
They can be available as a one-page chart, or in the form of swatchbooks
or color-matching fans. Typically there are two different types of color
charts: Color reference charts are intended for color comparisons and
measurements. Typical tasks for such charts are checking the color
reproduction of an imaging system, aiding in color management or visually
determining the hue of color. Examples are the IT8 and ColorChecker
charts. Color selection charts present a palette of available colors to
aid the selection of spot colors, process colors, paints, pens, crayons,
and so on – usually the colors are from a manufacturers product range.
Examples are the Pantone and RAL systems.
is an abstract illustrative organization of color hues around a circle,
which shows the relationships between primary colors, secondary colors,
tertiary colors etc.
is an additive set of colors used, like red, green and
blue. In a subtractive set of colors, mixing of pigments or dyes for
printing, the colors magenta, yellow and cyan are normally used. Primary
Color is a small, arbitrary set of pigmented physical media, lights or
purely abstract elements of a mathematical colorspace model. Distinct
colors from a larger gamut can be specified in terms of a mixture of
primary colors which facilitates technological applications such as
painting, electronic displays and printing.
is a color made by mixing two primary colors in a given color space.
Theory of Colours
is a book by
Johann Wolfgang von Goethe
about the poet's views on the nature of
colours and how these are perceived by humans. Published in 1810, it
contains detailed descriptions of phenomena such as coloured shadows,
refraction, and chromatic aberration.
is a body of practical guidance to color mixing and the visual effects of
a specific color combination. There are also definitions (or categories)
of colors based on the color wheel: primary color, secondary color and
, which is a color made by mixing full saturation of one
primary color with half saturation of another primary color and none of a
third primary color, in a given color space such as RGB, CMYK (more
modern) or RYB (traditional).
is the change in direction of wave
due to a change in its transmission medium.
are pairs of colors which, when combined, cancel each other out. This
means that when combined, they produce a grey-scale color like white or
black. When placed next to each other, they create the strongest contrast
for those particular two colors. Due to this striking color clash, the
term opposite colors is often considered more appropriate than
"complementary colors". Which pairs of colors are considered complementary
depends on the color theory one uses: Modern color theory uses either the
RGB additive color model or the CMY subtractive color model, and in these,
the complementary pairs are red–cyan, green–magenta, and blue–yellow. In
the traditional RYB color model, the complementary color pairs are red and
green, yellow and purple and blue and orange, though these pairings fail
the modern definition of complementary colors, as they produce a brown
color when combined. Opponent process theory suggests that the most
contrasting color pairs are red–green, and blue–yellow.
Roy G. Biv
or initials) for the sequence of hues commonly described as making up a
rainbow: red, orange, yellow, green, blue, indigo and violet.
Color Vision Testing
is the condition of possessing four independent channels for conveying
color information, or possessing four types of cone cells in the eye.
Organisms with tetrachromacy are called tetrachromats. In tetrachromatic
organisms, the sensory color space is four-dimensional, meaning that to
match the sensory effect of arbitrarily chosen spectra of light within
their visible spectrum requires mixtures of at least four primary colors.
Tetrachromacy is demonstrated among several species of birds, fish,
amphibians, reptiles, insects and some mammals. It was the normal
condition of most mammals in the past; a genetic change made the majority
of species of this class eventually lose two of their four cones.
SMPTE Color Bars
is a television test pattern used where the NTSC video standard is
utilized, including countries in North America.Why Do We See Color
Light - Prisms
This is Not a Rainbow
The existence of the rainbow depends on the
conical photoreceptors in your eyes
. To animals without cones, the rainbow
does not exist.
Light Darkness and Colours
About How Ink is Made
Cracking the Colour Code
Computer Color is Broken
Hindu spring festival celebrated in India and Nepal, also known as the
"festival of colours" or the "festival of love". The festival signifies
the victory of good over evil, the arrival of spring, end of winter, and
for many a festive day to meet others, play and laugh, forget and forgive,
and repair broken relationships. It is also celebrated as a thanksgiving
for a good harvest. It lasts for a night and a day, starting on the
evening of the Purnima (Full Moon day) falling in the Vikram Samvat Hindu
Calendar month of Phalgun, which falls somewhere between the end of
February and the middle of March in the Gregorian calendar. The first
evening is known as Holika Dahan or Chhoti Holi and the following day as
Holi, Rangwali Holi, Dhuleti, Dhulandi, or Phagwah.
Sadness Impairs Color Perception
Goethe on the Psychology of Color and Emotion
is the irrational fear of, or aversion to, colors.
How do we See Colors?
Did you ever look at a beautiful
painting or witness a gorgeous sunset and wonder, `How is it that I am able to
that?' What enables us to see the light and experience such wonderful shades
of color during the course of our everyday lives? Some may take seeing for
granted, but if the process is looked at closely, you can see what a wonder it
really is. First Things First...
What is Color?
Pure white light, such as sunlight, is composed of the visible colors. Sir Isaac
Newton discovered this in 1666 by passing a beam of light through a
renowned English scientist was 23 years old at the time. He was made to stay
home from Cambridge University for over a year because the plague that was
sweeping Europe had closed it down. It was during this period that Newton
performed his famous spectrum experiments. To alleviate the boredom of
quarantine, he punched holes in the curtains of his darkened room to study the
effects of light passing through a prism. The light separated into the same
progression of colors found in the natural rainbow. Although he found an
infinite number of colors in this spectrum, Newton wanted to show that there
were just seven main colors, like the seven known planets and the seven musical
notes in the diatonic scale. He identified red, orange, yellow, green, blue,
indigo and violet. This was also in keeping with Aristotle's seven classes of
color which he thought were all mixes of black and white. Using a second prism,
Newton showed that each color in the spectrum is monochromatic--that is,
composed of a single, unique wavelength which can't be further separated into
other colors. Newton's experiments showed that light can be combined to form
different colors. For example, combining blue and yellow light produces a green
light that appears identical to the pure green found in a prism spectrum.
(Modern techniques, however, show these greens to be two very different colors.
Such color pairs are called metamers because they appear to be identical even
though they have different wavelengths.) Using two prisms, Newton found that
some color combinations produce pure white instead of colored light. In effect,
they complete each other when mixed. These pairs of colors are called complements. In this example you see that purple and yellow lights combine to
How do we see Color?
The human eye
color. Light receptors within the eye transmit messages to the brain, which
produces the familiar sensations of color. Newton observed that color is not
inherent in objects. Rather, the surface of an object reflects some colors and
absorbs all the others. We perceive only the reflected colors. Thus, red is not
"in" an apple. The surface of the apple is reflecting the wavelengths we see as
red and absorbing all the rest. An object appears white when it reflects all
wavelengths and black when it absorbs them all. Red, green and blue are the
additive primary colors of the color spectrum. Combining balanced amounts of
red, green and blue lights also produces pure white. By varying the amount of
red, green and blue light, all of the colors in the visible spectrum can be
produced. Considered to be part of the brain itself, the retina is covered by
millions of light-sensitive cells, some shaped like rods and some like cones.
These receptors process the light into nerve impulses and pass them along to the
cortex of the brain via the optic nerve. Have you ever wondered why your
peripheral vision is less sharp and colorful than your front-on vision? It's
because of the rods and cones. Rods are most highly concentrated around the edge
of the retina. There are over 120 million of them in each eye. Rods transmit
mostly black and white information to the brain. As rods are more sensitive to
dim light than cones, you lose most color vision in dusky light and your
peripheral vision is less colorful. It is the rods that help your eyes adjust
when you enter a darkened room. Cones are concentrated in the middle of the
retina, with fewer on the periphery. Six million cones in each eye transmit the
higher levels of light intensity that create the sensation of color and visual
sharpness. There are three types of cone-shaped cells, each sensitive to the
long, medium or short wavelengths of light. These cells, working in combination
with connecting nerve cells, give the brain enough information to interpret and
name colors. The human eye can perceive more variations in warmer colors than
cooler ones. This is because almost 2/3 of the cones process the longer light
wavelengths (reds, oranges and yellows).About 8% of men and 1% of women have
some form of color impairment. Most people with color deficiencies aren't aware
that the colors they perceive as identical appear different to other people.
Most still perceive color, but certain colors are transmitted to the brain
differently. The most common impairment is red and green dichromatism which
causes red and green to appear indistinguishable. Other impairments affect other
color pairs. People with total color blindness are very rare. Birds, fish and
many other mammals perceive the full spectrum. Some insects, especially bees,
can see ultraviolet colors invisible to the human eye. In fact, color
camouflage, one of nature's favorite survival mechanisms, depends on the ability
of the predator to distinguish colors. The predator is expected to be fooled by
the color matching of the prey. Until recently, it was thought that dogs didn't
see any color at all. Recent studies now show, however, that dogs can
differentiate between red and blue and can even pick out subtle differences in
shades of blue and violet.
Before the topics of
and color can
be explored, there must first be an understanding of
. Waves have high and
low points, and the distance between one of those highs and lows and the next is
called a wavelength. Just how long that wave is will determine the amount of
energy that it has. For example, a long wave has a low amount of energy or low
frequency, and a short wave has a high amount of energy or high frequency. What
we see in a rainbow, then, are the wavelengths of the visible colors. You see,
our sun emits its radiation in this visible range, which our eyes interpret as
the colors of the rainbow. These colors are identified as the visible spectrum
and are often times remembered as ROY G. BIV:
red, orange, yellow, green, blue,
indigo, and violet. Wave Travel
It sounds logical so far, but how are these
related to light and
color? Light travels in the form of a wave. It is basically
energy or particles), and mostly moves as waves. White light, or the light from
, is made of colors, and colors are different types of light recognized
by their own wavelengths
. Waves exist above and below the visible spectrum, too.
Such waves called radio, microwave, and infrared are below the red end of the
spectrum, and ultraviolet (UV), x-rays, and gamma rays are above the violet.
These cannot be seen by the human eye, and therefore constitute the "invisible"
spectrum. Together, the visible and invisible spectrums make up the
are three things that can happen to a light wave. It can be reflected, absorbed,
or transmitted. This is determined by the object that the wave hits, and that
will give it its color. For an object to be black, it means that all the
wavelengths of light hitting that object are absorbed; no light is reflected.
Solid objects, for the most part, will reflect light, and transparent objects
will transmit light through them. To illustrate this last fact, place a glass of
red fruit juice on a table. Hold a piece of white paper on one side of the glass
and chances are, if the light in the room is right, you will see red on that
piece of paper. The light transmitted the red color of the juice onto the paper.
Color from Light
The color of anything depends on the type of light sent to our eyes;
is necessary if we are to have any
perception of color at all. An object is "colored," as stated above, because of
the light it reflects—all other colors are absorbed into that specific object.
So then, an apple appears red because it reflects red light
. White light from
the sun contains all the possible color variations
. Yet, the human eye can only
respond to certain colors and wavelengths, and not everyone sees the same colors
or exact same shades of a color. We are capable of seeing color because our
have light and color-sensitive receptors. These receptors are called rods
(receptive to amounts of light) and cones (sensitive to colors). Being able to
see color is a sensation, just like smelling a pie fresh out of the oven or
tasting your favorite meal. Different foods smell and taste different to each
person, and likewise, no color is seen exactly the same by two people, because
each person's rods and cones vary.
Colors are in the Light
is a material
that changes the color of reflected
as the result of
-selective absorption. This physical process differs from
fluorescence, phosphorescence, and other forms of
, in which a
light. Pigments have
, and molecules either
certain wavelengths of light or reflect
certain wavelengths of light, and
if a pigment reflects
a certain wavelength of light, then that is what
you will see. For objects that have no pigments, like animals, then
the shape and size of its surface
either absorbs certain wavelengths of
light or reflects certain wavelengths of light, and if the
reflects a certain wavelength of light
, then that is what color you will
see. Blue has a short wavelength
red has a longer wavelength
and yellow and green
is in between red and blue.
is the part of a molecule responsible for its color. The
color that is seen by our eyes is the one not absorbed within a certain
wavelength spectrum of visible light. The chromophore is a region in the
molecule where the energy difference between two separate molecular
orbitals falls within the range of the
. Visible light that hits the chromophore can thus be absorbed
by exciting an electron
from its ground state into an excited state. In biological molecules that
serve to capture or detect light energy, the chromophore is the moiety
that causes a conformational change of the molecule when hit by
Colors Appearance Changes when near certain Colors
The Color Factor
The impact that a color has depends on a combination of three factors: hue,
saturation, and luminance. Hue simply means the actual shade or color,
saturation is just how pure the hue is, and luminance is what is described when
we say that a color is either light or dark.
Complementing colors also have to be considered if you are seriously
pondering color combinations. They highly contrast each other, and when placed
side by side, enhance the color of the other. Color complements are on opposite
ends of the color wheel; they also happen to have drastically different
Some people have trouble discerning colors, along with their shades and luminance. Color
blindness is a color perception problem whose most common ailment is a red-green
deficiency. This means that there is a lack of red or green photopigments and
people have difficulty making out colors that are based on the `red to green'
ratio. It is estimated that about 7% of all males are color blind, while
only .4% of women are affected. This is because the defect is linked to the
X-chromosome, of which males only have one, so there is less chance of it being
naturally corrected by the genes.
"Shadowing" Light and Color
All of us have the potential to see light and colors "in a different
so to say—even if we aren't color blind. Trace a ray of light from a point on a
solid object to a light source. If the ray of light hits another object before
you get to the light source, the point is in shadow. A shadow, present in an
area where there is less light, must be opposite a light source. The light,
object, and shadow will all be in a line. This is because light moves in
straight lines. Shadows are caused by objects blocking light from a bright
source. Materials may block some (translucent), all (opaque), or none
(transparent) of the light hitting them. We can see that shadow influences the
light that we are able to see, but we should also know now that this means the
colors of objects will be altered as well. Since color depends on the light
that we see, if some, all, or none of that light is blocked, some, all, or none
of the colors will be changed. Shading makes colors appear darker, since the
luminance (darkness or lightness) is altered. Since the sun's light contains all
the color possibilities, changed light will change colors as well.
How does color affect us?
Our personal and
cultural associations affect our experience of color. Colors are seen as warm or
cool mainly because of long-held (and often universal) associations. Yellow,
orange and red are associated with the heat of sun and fire; blue, green and
violet with the coolness of leaves, sea and the sky. Warm colors seem closer to
the viewer than cool colors, but vivid cool colors can overwhelm light and
subtle warm colors. Using warm colors for foreground and cool colors for
background enhances the perception of depth. Although red, yellow and orange are
in general considered high-arousal colors and blue, green and most violets are
low-arousal hues, the brilliance, darkness and lightness of a color can alter
the psychological message
. While a light blue-green appears to be tranquil, wet
and cool, a brilliant turquoise, often associated with a lush tropical ocean
setting, will be more exciting to the eye. The psychological association of a
color is often more meaningful than the visual experience
. Colors act upon the
body as well as the mind. Red has been shown to stimulate the senses and raise
the blood pressure, while blue has the opposite effect and calms the mind.
People will actually gamble more and make riskier bets when seated under a red
light as opposed to a blue light. That's why Las Vegas is the city of red neon.
For most people, one of the first decisions of the day concerns color harmony.
What am I going to wear? This question is answered not only by choosing a style
and fabric appropriate to the season, but by making the right color choices. And
it goes on from there. Whether you're designing a new kitchen, wrapping a
present or creating a bar chart, the colors you choose greatly affect your final
results. How often have you caught your breath at the sight of a flowerbed in
full bloom? Most likely the gardener has arranged the
according to their
color for extra vibrancy. Have you ever seen a movie in which a coordinated
color scheme helps the film create a world unto itself? With a little knowledge
of good color relationships, you can make colors work better for you in your
business graphics and other applications. Color is light and light is energy.
Scientists have found that actual physiological changes take place in human
beings when they are exposed to certain colors. Colors can stimulate, excite,
depress, tranquilize, increase appetite and create a feeling of warmth or
coolness. This is known as chromodynamics
. An executive for a paint company
received complaints from workers in a blue office that the office was too cold.
When the offices were painted a warm peach, the sweaters came off even though
had not changed. The illusions discussed below will show you
that sometimes combinations of colors can deceive the viewer, sometimes in ways
that work to your advantage. They can also cause unfortunate effects in your
graphics, so be sure to watch out for these little traps. Sometimes colors
affect each other in unexpected ways. For example, most colors, when placed next
to their complements, produce vibrating, electric effects. Other colors, in the
right combinations, seem quite different from what you'd expect. The most
striking color illusions are those where identical colors, when surrounded by
different backgrounds, appear to be different from each other. In a related
effect, different colors can appear to be the same color when surrounded by
certain backgrounds. When you look at a colored object, your brain determines
its color in the context of the surrounding colors. In this picture, the two
bows are the same color, but because the surrounding areas are strikingly
different in contrast, it seems to our eyes that they are different. Keep this
effect in mind when creating graphics where color matching is critical. If you
attempt to match your corporation's official colors, you may find that even if
you achieve an exact match, it may look wrong in context. In the same way that
one color can appear different in different surroundings, two similar colors may
appear to be identical under some conditions. Even though the two symbols are
actually slightly different tones, the contrasting backgrounds cause our brains
to think that they are the same color. This effect is harder to control, but be
aware of it because it can affect your graphics in hidden ways. The feeling you
get when looking at bright complementary colors next to each other is a
vibrating or pulsing effect. It seems that the colors are pulling away from each
other. It's caused by an effect called color fatiguing. When one color strikes a
portion of the retina long enough, the optic nerve begins sending confused
signals to the brain. This confusion is intensified by the complementaries.
Mixing brilliant complementary colors gets attention, but it should be used with
restraint. The effect is disconcerting and can make your eyes feel like they've
been shaken around. If you want to use complementary colors without causing
discomfort, you can outline each of the colors with a thin neutral white, gray
or black line. The outlines separate the two colors, which helps your brain keep
them separated. When two very similar colors touch in an image, both colors
appear to wash out and become indistinct. This is because the borders between
the colors are difficult to distinguish and your brain blurs the colors
together. If you outline each of the colors with a thin neutral white, gray or
black line, the colors become easier to distinguish. This is called the stained
glass technique and is a way to reduce this blurring of the colors.
Coloring Vision, Appetite, and Mood
If you think colors are pretty to look at but have no real impact on people, think again. Certain colors
are known to have definite
behavior-altering capabilities. Some colors or
combinations of them irritate eyes and cause headaches. For example, bright
yellows—either on walls or as the background on a computer screen—are the most
bothersome colors and are not calming or relaxing in any way. Bright colors
reflect more light, so yellow over-stimulates our eyes, causing strain and even
irritability. You wouldn't ever want to paint a baby's room yellow, but you
could certainly use it on important street signs to attract attention. Other
colors can alter how or what we eat. Blue is known to curb appetites. Why is
this so? Blue food doesn't exist in nature, with the exception of the blueberry.
There are no blue vegetables, and hopefully, if you encountered a blue meat, you
certainly wouldn't eat it. Because of this natural color deficiency, there is no
automatic appetite response to anything blue. There are colors that can put us
in a better mood, too. Green is the most restful color for the eye. It has the
power to soothe and comfort. Studies have even shown that people who work in
surroundings that are green experience fewer headaches, stomach aches, and other
signs of sickness or fatigue.
Out of Sight!
Besides being pretty to look at, colors and the light they come from really do have the power to impact
people in many ways. Along with the aesthetics of light and color, there is
real science behind each and every sight we see. Each flash or ray of light,
each shade of color that light makes visible, and each time our eyes receive the
messages to see them, we are reminded of a special relationship—one that is
often overlooked because we simply take seeing for granted. We miraculously
experience a bright, vivid world because of the workings of our eyes, the
wonders of light, and the brilliance of color.
What are the Color Characteristics?
There are literally millions of colors! But fortunately, they can be divided into just
a few color families. And every color can be described in terms of having three
main attributes: hue, saturation and brightness.
Hue is identified as the
color family or color name (such as red, green, purple). Hue is directly linked
to the color's wavelength.
Saturation, also called "chroma," is a measure
of the purity of a color or how sharp or dull the color appears.
Brightness, also called "luminance" or "value," is the shade (darkness) or tint
(lightness) of a color. Areas of an evenly colored object in direct light have
higher brightness than areas in shadow.
The concept of the color wheel was invented when Sir Isaac Newton bent the
color spectrum into a circle. Since then, the color wheel has been used as a
tool for understanding color relationships and creating harmonious color
schemes. The color wheel clearly shows which colors are warm and cool,
complementary, split complementary and analogous. The diagrams in the following
pages demonstrate each of these concepts.
Cool colors range from blue to
violet, the half of the color wheel with shorter wavelengths. Cool colors have a
calming effect. They are frequently used for backgrounds to set off smaller
areas of warm colors. Used together, cool colors can look clean and crisp,
implying status and calm. However, it is important to note that usage of bright
cool colors generates more excitement than light, medium or dark cool colors.
Warm colors range from red to yellow, essentially the half of the color
wheel corresponding to the longer wavelengths. Warm colors are active,
attention-grabbing and aggressive. They stimulate the emotions, motivate and
seem to come forward off the screen or page.
Complementary colors lie
opposite each other on the color wheel. They complete or enhance each other.
Impressionist painters in the 19th century often placed dots of pure
complementary pigment on a color's surface to make the color come alive. While
the dots weren't apparent to the viewer, the color appeared especially vibrant.
When mixed together equally, subtractive complements, such as paints, should
theoretically produce black or gray. In practice, the pigments are never perfect
and the result is a muddy brown instead.
Using complementary colors in an
image is quite pleasing to the eye. The colors seem to belong together. The most
effective use of complements is to let one of them dominate by giving it a
bigger area or a fuller saturation, while using the other as
Split complements (also known as contrasting colors or triads)
lie on either side of a color's complement on the color wheel. These colors
offer many of the same benefits as complementary colors, but the effect is more
subtle. As two of the colors will be very similar, using fully saturated
colors may be too strong. Dilute the saturation by using darker shades or
lighter tints to draw the colors together.
Analogous color schemes use
colors that are adjacent on the color wheel and so have similar hues. For
example, blues, blue-greens and greens are analogous. When using analogous
colors in a presentation, make one color dominant to avoid confusion and use the
other colors as accents.
A monochromatic color scheme uses a single hue
with variations in the saturation and brightness only. Such a color scheme
produces simple images with no discord. However, if you plan to use
monochromatic colors for your business graphics, make sure that you have the
contrast necessary to make clear distinctions for the audience and to emphasize
the important points. This is also important for achromatic graphics, which use
white, black and shades of gray.
Achromatic color schemes have no color.
They use black, white and shades of gray to represent colors. It may be that
while your graphics will be presented in color, you'll need to produce
black-and-white handouts. If so, review each handout carefully for legibility,
as colors don't always translate to grayscales as expected. If a grayscaled
image isn't clear enough, consider replacing blocks of color with patterns to
Color HarmonyIn art as well as music, harmony comes
from a pleasing arrangement of the parts. The science of color harmony traces
its roots back to 1893 when Chevreul's "The Principles of Harmony and Contrast
of Colors," was published.
The science of color harmony categorizes
colors and determines harmonious groupings, such as complements, split
complements, triads and analogies. Where science becomes art is in knowing how
to use these colors, in what proportions and in what order. In color and music,
contrasts intensify each other. Complementary colors bring out the attributes of
each other. White becomes brighter on a black background, blue enhances the
warmth of orange; opposite hues are especially attention-getting. This hue
contrast can cause tension in the image, if you are using fully saturated
colors. Complementary colors can be brought into harmony by reducing the
saturation or by mixing a little of each color with the other. This tension is
at its strongest when large areas of complementary colors touch. Leonardo di
Vinci was the first to study this effect, known as simultaneous contrast. For
the most part, it's visually disturbing and should be avoided. Separating large
areas of complementary colors with a thin line of neutral white, gray or black will diminish the effect.
Varying the saturation
or brightness of a color can cause light and dark contrasts. By simply working
with complementary and analogous colors, a harmonious color scheme can easily be
created. Pay attention to the saturation and brightness of the colors to prevent
unexpected contrasts or to create intentional ones. If two colors are equal in
saturation and proportions, the dominant color will be the one whose brightness
is furthest from the background's. Similarly, if two colors have identical brightnesses, the dominant
color will be the one whose saturation deviates more from that of the
When you ask children to tell you the names
of all the colors, they'll know red, blue, yellow and a few more. A more
sophisticated adult will be able to name periwinkle, mauve, fuchsia and maybe
another hundred. There are, however, thousands of regularly used colors and
millions more that can be distinguished by the human eye. To give a name to each
of them would be impossible, so scientists have devised various ways of
assigning numeric values to colors. These systems are called color models, and
they provide precise methods for naming and reproducing exact colors. Some are
based on the optical components of the colors and others are based on how people
"feel" colors are related to each other.RGB (RED, GREEN, BLUE) MODEL
In the RGB system, the red, green and blue dots are assigned
brightness values along some scale, for example 0 to 255, where 0 is dark and
255 is bright. By listing the three values for the red, green and blue
phosphors, you can specify the exact color that will be mixed. Additive colors
get lighter when mixed. As each component of light is mixed in, the combination
becomes a new color. Red, green and blue are the three additive primaries. You
can mix any color of light with different combinations of the additive
primaries. When you mix all three together in balanced amounts, you get white.
These three primaries are the basis of the additive color model. It's called the
RGB model, and it's usually used to create color on your computer display as
well as other electronic devices. By mixing together various amounts of red,
green and blue light, you can make almost any color. The RGB color space is a
multi-colored cube with different points showing what colors different mixtures
of red, green, and blue make. Television screens and computer monitors make
their colors by mixing red, green and blue lights. A monitor or television
screen mixes a color by illuminating tiny dots of red, green and blue phosphors
with an electron gun located at the back of the monitor. By illuminating each of
the dots to a different brightness, the monitor creates different colors. The
next several pages have descriptions of the major color models and some
experiments to help you visualize how they work. Because the RGB model is only capable of producing a certain range, or gamut, of
colors, there are some colors that cannot be reproduced accurately by a
computer monitor. The number of colors visible on a monitor is further reduced
by the limitations of the video hardware in the computer, which may display
anywhere from just black and white up to 16.7 million colors. Cyan, magenta
and yellow are the three subtractive primaries. Nearly any color can be produced
with different combinations of these three colors. When you mix all three
together in equal amounts, you get a near black. These three primaries are the
basis of the subtractive color model. That's why it's called the CMY model. A
close relative of the CMY model, called CMYK, is commonly used by printers and
CMYK (Cyan, Magenta, Yellow, Black) Model
Many computer printers and traditional "four-color" printing presses use the CMYK
model. In the CMYK model, by using cyan, magenta, yellow and black inks or
paints, you can mix nearly any color.
In theory, you can mix any
reflective color by mixing a combination of cyan, magenta and yellow. In the
real world, however, the inks that printers use are not perfect. This becomes
most obvious when you mix all three to make black. The color that results is
muddy brown, due to impurities in the inks. That's why printers use black ink to
get the best results. Subtractive colors get darker when mixed. Each of the
mixed paints or inks absorbs different components of the light. If the right
combination of paints is mixed together, all of the components of light are
absorbed and the result is a near black.
When preparing a color image for
printing, the prepress operator makes four separation plates. Each plate is for
one of the four colors of ink in the CMYK
model. When all four plates are aligned and printed on top of each other, the
inks will combine to simulate the proper colors. This method is referred to as
"process color" (or "four-color") printing.
HSL (Hue, Saturation, Luminance) Model
The HSL model is very similar to the RGB model.
In fact, when they're expressed mathematically, they're identical. The
difference lies in how colors are expressed numerically. The hue determines
which basic color it is. Red, green, blue, yellow, orange, etc. are different hues. Saturation and luminance tell more about the variations of these basic
colors. Saturation is the vividness (or "purity") of the color, i.e., how much
of the color's complement is mixed in. Finally, luminance refers to the
"whiteness" of the color. It may also be termed "brightness," "value" or
Other models related to the HSL
model are the HSB (Hue, Saturation, Brightness) and HSI (Hue, Saturation,
Intensity) models. These terms are all similar but not interchangeable.
CIE (Commision Internationale l'eclairage) Model
The CIE model is a more subjective description than the others. In 1931, the Commision Internationale l'Eclairage
tested many people and found that the sensitivity of the receptors in the eye
caused certain colors to be associated with others. The CIE color space includes
all visible colors, whether or not they can be defined in the RGB or CMYK
models. Computer printers and other devices for displaying color have practical
limitations that prevent them from making ALL of the visible colors. The colors
that they CAN create are collectively called the color gamut. The CIE model is
useful in part because a printer's color gamut can be drawn on the CIE color
space showing what colors cannot be printed. Other color models closely related
to CIE are UCS (Uniform Color Space), CIELAB and CIELUV.
PANTONE® COLOR REFERENCE SYSTEMS
The PANTONE MATCHING SYSTEM® is a solid color
communication system based on the visual matching of individual, pre-mixed
colors. The PANTONE MATCHING SYSTEM is a series of books with thousands of
precisely printed colors alongside printers' formulas for mixing those colors.
The PANTONE MATCHING SYSTEM is used by artists and commercial printers to
select, specify and match colors very precisely.
Many logos are created with specific PANTONE Colors that can be very closely
reproduced. By using PANTONE Colors, designers can be confident that their
output will match their expectations. The original PANTONE MATCHING SYSTEM
included 504 colors and has since been expanded to include 1,012 colors along
with their printing ink formulations. For four-color (CMYK) printing, the
PANTONE Process Color System® specifies more than 3,000 colors and shows the
screen percentages for printing. Recently, as computers have been used more
extensively for business and professional graphics, software users have begun to
specify their colors with the PANTONE MATCHING SYSTEM and the PANTONE Process
Color System. More and more software products have been licensed by Pantone,
Inc. to ensure a greater degree of consistency throughout the industry.
More recently, Pantone has introduced a revolutionary,
patented six-color process printing system called Hexachrome. By providing an enhanced set of Cyan,
Magenta, Yellow and Black, plus the addition of PANTONE Hexachrome® Orange and
PANTONE Hexachrome Green, the color gamut for reproducing printed photographic
images and simulated spot colors has been substantially increased. One of the
inherent short-comings of printing with CMYK (commercially and/or digital
printers) is that the resultant color gamut is relatively restricted, resulting
in a considerable loss of color from the original artwork. In fact the
four-color (CMYK) gamut can only reproduce 50% of the spot/solid PANTONE
MATCHING SYSTEM Colors. With Hexachrome, you can now reproduce over 90% of these
spot/solid colors, and get a substantially enhanced reproduction of the
photograhic images. how can we reproduce color?
Colorful graphics get the
attention and the professional admiration of your viewers, but producing color
graphics on the computer used to be so time consuming and expensive that it was
only used for professionally published work. Now that the technology has become
accessible to even casual users you may find yourself expected to produce
colorful handouts, slides or reports on a regular basis. For some purposes, it
is sufficient to be able to display your graphics on screen and show them
informally. In a meeting, you may need to print out a few copies as handouts.
Occasionally you'll need to publish hundreds or thousands of copies to
distribute more widely.
The Color Wheel
Although most of the time we don't even think about color
consciously, some people think about and plan colors very seriously. Whether it
be a dress maker color coordinating fabrics, a painter imagining the perfect
eye-pleasing portrait, or someone simply redoing their living room, a color
wheel can be very useful. A color wheel is a tool that helps artists and others
learn and visualize color relationships; it shows how primary colors can combine
to create many other colors.
An artist's traditional color wheel has 12
colors: 3 primary, 3 secondary, and 6 tertiary. Some materials let certain
colors pass through them, and absorb other colors. These materials are called
dyes or pigments. The primary colors of pigment are red, blue, and yellow.
Mixing these primary colors of pigment gives us the three secondary colors:
red+blue=violet, red+yellow=orange, and yellow+blue=green. Then, the primary
colors mixed with the secondary give us the tertiary. They are: red- violet,
red-orange, yellow-orange, yellow-green, blue-green, and blue-violet.
The primary colors of light are red, blue, and green, and
the secondary are yellow, cyan, and magenta. It is very important to know that
mixing pigment and mixing light are very different. Red and green paint, for
example, make brown paint, but red and green light make yellow light. When beams
of light are mixed without any absorption, an additive process occurs. The more
we mix the beams, the closer they get to being white light. However, when we put
light through a color filter, a subtractive process occurs. Some wavelengths of
light are being absorbed (subtracted) and we only see the wavelengths that are
selectively given off. The Additive and Subtractive Models are explained further
As stated previously, the primary colors of light are red, blue, and green. These occur in the Additive
Color (RGB) Model, so named because black is the base and light is "added" to
eventually get to white, which is all of the colors together. Additive colors
are seen in televisions, nature, and the computer screen you are looking at
right now. Amazingly enough, colors are perceived in our eyes and brains by a
three-color code; three different particles in the retina are sensitive to—you
guessed it—red, blue, and green. Just as any color of the spectrum can be
made by mixing the three primary colors, so do our own eyes discern the various
colors by sensing different wavelengths with these three receptors.
The Subtractive Color (CMYK or CMY) Model is used for printed publications. There
are only four colors that offset the printing process. The subtractive colors
are also the secondary colors in light: cyan, magenta, and yellow. Black is used
in the subtractive model as well, because cyan, magenta, and yellow make more of
a dark gray than pure black when they are combined. In the Subtractive model,
light reflected off a surface is what the surface doesn't absorb.
No matter how you intend to show your computer
graphics, you'll see them first on a
. All monitors have
limitations that you should know about before you begin. Most color computer
monitors work on the same principle as a television. The screen is composed of
phosphor dots that are illuminated from behind. On a color monitor, red, green
and blue dots are distributed evenly. These dots are illuminated to
different brightnesses to mix the
different colors you see on the screen. If you look very closely, you can see
these individual dots. Most computer display systems are made up of two
components: the monitor and a video adapter card that resides in the computer
itself. The quality of the display is affected by both the monitor and the video
card. Besides the size of the screen, computer display systems have two primary
features that determine the quality of the image: resolution and color depth.
Resolution determines the fineness of detail on the screen. The color depth
determines how much control you have over the coloring of your graphics. The
video card determines how many colors can be displayed by the monitor. Since the
colors are created by mixing different brightness levels for each of the three
color dots, a monitor can only mix as many colors as the number of brightness
combinations it can make. The number of colors that can be displayed by a video
card is called its color depth and is usually specified in bits per pixel. Color
depths in commercial video cards range from black and white (one bit) to over 16
million colors (24 bits). Of course, the human eye can't distinguish that many
colors, so these higher-end displays are more powerful than most people need.
When designing on the desktop, your first concern is to assure that you are
seeing color on your monitor as accurately as possible. The PANTONE Personal
Color Calibrator™ software gives you the ability to set the manufacturer's
standard profile for a specific brand and model of monitor, but further lets you
set up and save your personal preference for red/green/blue acuity, brightness,
contrast and lighting conditions. In many cases, the number of colors in an
image will exceed the capabilities of the device used to display the image. For
example, it may be necessary to present a 256-color image on a 16-color display
system, or to print a scanned photograph on a low-end dot-matrix printer. In
situations such as these, the image is automatically simplified to reduce the
number of colors. This process is referred to as color reduction. As a typical
user, you don't need to worry about doing the color reduction. That's usually
done for you by the computer system or your software application. Color
reduction takes its toll on the quality of your displayed images, however, and
you will probably notice these effects in your work. Color reduction typically
uses a technique called dithering. In the same way that the monitor simulates
individual colors with its red, green and blue dots, even more colors can be
simulated by arranging individual pixels. This technique creates a coarse image
which will only look good at a distance. Over the years, a wide variety of
dithering methods (or algorithms) have been developed and implemented for use in
image processing. The choice of any particular method depends on the exact
nature of the image, the display system and the desired results. Dithering
usually creates various distracting patterns (called artifacts or moirŽ
patterns) in the image. Some dither patterns produce better gradations and
shading than others, but may require more processing time and memory. When
designing for Web site displays, you can reduce the effects of dithering and
provide more consistent color on different monitors if you use the 216
"internet-safe," non-dithering colors. Pantone's ColorWeb® and ColorWeb® Pro
software packages help you select and incorporate these colors in the popular
Web authoring software programs.
Color Photos at home remember there are some important variables to be aware of
Photo Paper. Each type of
paper reacts differently (glossy, matte, soft gloss) you could even have a bad
batch of photo paper so don't always assume that it's the printer, software or
the photo itself.
Printer Settings. You could even have a bad ink cartridge or the wrong color profile.
Software that you use to Print
and Edit the photo.
Photo Editing Software
Scanner settings if the photo is scanned. Scanners
Colors and Monitor Colors: The Photo may
also have slight color variations that you don't notice on your PC Monitor
not always adjusted properly or calibrated properly and may not see the certain
colors correctly. If you send a color to someone else they might see a
different shade of that color on their monitor compared to what you see on your
monitor. And what colors you see on your monitor might not be the same colors
Monitor Test Images
Calibrate Your Monitor for Color
Calibration of LCD, CRT, Projector & Notebook Monitor Displays
) is a measure of spatial printing
or video dot density, in particular the number of individual dots that can
be placed in a line within the span of 1 inch (2.54 cm).
96 px for every inch on your
100×100 pixel image
that is printed in a 1cm square has a resolution of 100 pixels per centimeter (ppcm).Pixel
is a physical point in a raster image, or the smallest addressable element
in an all points addressable display device; so it is the smallest
controllable element of a picture represented on the screen. The address
of a pixel corresponds to its physical coordinates. LCD pixels are
manufactured in a two-dimensional grid, and are often represented using
dots or squares, but CRT pixels correspond to their timing mechanisms.
are measurements of the pixel density (resolution) of an electronic
image device, such as a computer monitor or television display, or image
digitizing device such as a camera or image scanner. Horizontal and
vertical density are usually the same, as most devices have square pixels,
but differ on devices that have non-square pixels.
or display modes of a digital television, computer
monitor or display device is the number of distinct pixels in each
dimension that can be displayed. It can be an ambiguous term especially as
the displayed resolution is controlled by different factors in cathode ray
tube (CRT) displays, flat-panel displays (including liquid-crystal
displays) and projection displays using fixed picture-element (pixel)
is the detail an image holds. The term applies to raster digital images,
film images, and other types of images. Higher resolution means more image
is a numeric representation of (normally binary) a two-dimensional image.
Depending on whether the image resolution is fixed, it may be of vector or
raster type. By itself, the term "digital image" usually refers to raster
images or bitmapped images.Binary
is a digital image that has only two possible values for each pixel.
Typically, the two colors used for a binary image are black and white,
though any two colors can be used. The color used for the object(s) in the
image is the foreground color while the rest of the image is the
background color. In the document-scanning industry, this is often
referred to as "bi-tonal".
What is an image
There are many variables that could have effects on the quality of your finished
printed photo. So experiment with the
settings of your printer, Software and also try different paper. Most important
make one change at a time and write down all your changes and findings so that
you can learn what settings and paper make the best photographs. When achieved
you can print out some really great photos at home and have more control over
the quality and price, providing you have a nice
of course that specializes in
In Photoshop you can mouse over a color to see its
color balance (under the Info tool bar) if you need to match it with a
If your color
is off on your printed photo you have a few things you need to check.
Make sure your monitor
screen colors are correct and calibrated so that you can see the colors in your
photo as they are.
Print a color test page
(under printer options or maintenance) If colors are correct save your color
test page for future reference to compare to a new test page if suspecting a
Check printer cartridge
(sometimes you can get a bad cartridge, if you do, switch cartridge's to see if
that's the problem. You might have to try your deep cleaning option for your
printer head, (under printer maintenance) and print out a color test page to
make sure each color looks OK. Make sure printer head is aligned (under
It's better to adjust your photo in
Adobe Photoshop Elements 7
or in other photo editing software instead of using your printer settings to get
desired effects. Printer settings should mostly be adjusted for Paper type, size
(portrait or landscape), extra fine and photo.
If you do have a nice
Photo Editing Software then you should be able to mouse over the color in
question and see the color balance in the photo information tab in both
RGB & CMYK
. Then you can compare that color to
known colors for verification.
For optimum results make sure your photo is close to
before printing, especially if you're
resizing the photo.
Even though "PictBridge"
(camera to printer technology) is convenient, it's is always better to see your
photo full screen on a 15" Monitor before printing. This way you're sure you're
printing a good photo the way you want it without wasting paper & ink.
your photos using software like
for best results.
If you want to print your graphics on paper but only need a few copies, you
need a color printer for your computer. The cost and quality of these printers
has been improving dramatically since they were first introduced, leaving you
with quite a few choices. The four primary printer technologies for producing
color output vary in cost, resolution, color depth and paper requirements.
Individual printers also vary in quality, speed, reliability and
lifespan.Pantone has several software packages that can help you manage and
control color on the desktop. PANTONE ColorDrive® and PANTONE ColorReady™ are
designed to work with popular graphic design programs like Quark XPress™,
Photoshop®, Illustrator® and the like, and also provide more accurate output on
a wide range of desktop printers. The company also offers PANTONE OFFICECOLOR
ASSISTANT™ which allows the reduction and use of PANTONE MATCHING SYSTEM® Colors
in Microsoft® Word, Excel and Powerpoint to assist the business manager in
producing more attractive presentations and reports.
If you need to produce hundreds or thousands of copies
of your work, you will need to take your output to a commercial printer for a
large press run. This process is somewhat demanding and expensive, but is
the only way to make large numbers of copies. Commercial printing requires quite
a bit of prepress work for each job. Producing camera-ready originals is
somewhat technical, so most printing houses have full-time prepress technicians
who can do some or all of the work for you, depending on your experience and budget. When you are deciding what type of
printing to do, speed, cost per copy and quality of the output are some of the
deciding factors. The printer's estimator can advise you about the choices
available. There are two different ways color can be applied to paper in color
printing: spot color and process color. Spot color is a method of applying a
premixed color of ink directly to the page. Process color applies four or more
standard ink colors (the basic four are cyan, magenta, yellow and black) in very
fine screens so that many thousands of colors are created. Spot color is usually
used when a few exact colors are needed. Process color is more useful for
printing photographs, paintings and very complex colored images. In some cases,
both spot color and process color can be used on the same document. For example,
a company brochure may include color photos (process color) and a corporate logo
(spot color). Spot color applies a premixed ink to the page. This color is
usually identified by a color system such as the PANTONE MATCHING SYSTEM. Spot
color is useful for documents that require only a few colors, such as
newsletters, brochures and stationery. Spot color is also used to match specific
colors very closely. The cost of printing color documents is related to the
number of ink colors used. As process color requires four or more inks, spot
color can be cheaper if you use fewer than four colors. Spot color also has the
advantage of printing a wider range of clean, bright colors. Look around you for
an example of spot color printing. If a color seems smooth and even no matter
how closely you look, it's probably printed with spot color. Process color is a
method used to create thousands of colors using four or more standard inks. The
colors used in four-color process are the three subtractive primaries (cyan,
magenta and yellow) plus black.The original image is separated into its cyan,
yellow, magenta and black components. A film is made for each separation and
then a plate is produced from the film. The paper is run through the four
stations of a four-color press to accept layers of ink from each plate. When all
four colors are printed together, the illusion of continuous color is
complete.More recently Pantone has patented a unique six-color process printing
technology called Hexachrome®. By incorporating an enhaced set of cyan, magenta,
yellow and black and adding PANTONE Hexachrome® Orange and PANTONE Hexachrome
Green, the reproduction of photograhpic imagery can be substantially enriched.
Additionally, nearby all the solid PANTONE MATCHING SYSTEM Colors can be
accurately simulated, thus eliminating the need to supplement the image
reproduction with several spot colors, scanning, designing, seperating, proofing
and printing. Take a look around you for a full-color newspaper, book or
magazine. If you look very closely at a color photograph, you can make out the
halftone dots of the four inks. If you are printing in process color, your image
will require a plate for each of the cyan, magenta, yellow and black inks. As
each color of ink used is laid down on the paper individually, a different plate
must be created for each ink. Spot colors each require their own plate as well.
Separations can be created in quite a few different ways. You may be asked to
provide a full color printout to be optically separated. Your image will either
be scanned or run through a separator, which separates the image using filters.
On the other hand, you may be asked to provide a disk containing the graphics
file. An imagesetter, which is essentially a very high-resolution printer, will
create the separations directly from the graphics file. Halftoning is the most
common of the many ways printers create different shades of color from just one
ink. A finely etched screen is used when making each plate. This screen changes
the darker and lighter areas of the original into areas of larger and smaller
dots. When printed, the larger dots will appear darker than the smaller dots,
due to greater ink coverage. When multiple colors of ink are printed together,
the different apparent shades will combine to simulate far more colors than are
actually used. Halftoning is done with a very fine screen when printing on
glossy paper and for higher quality documents. Coarser screens are used for
rough paper such as newsprint. Newspapers use coarse screens, so it's fairly
easy to make out the individual dots in newspaper photographs. The fineness of
halftone screens is determined by the number of lines of halftone dots per inch.
This is called the "lines per inch" or the LPI. Lithography means
"stone-writing." Invented in 1799 by Aloys Senefelder in Germany, this process
relies on the fact that water and grease repel each other. A lithograph stone is
prepared by drawing the image to be printed on polished limestone with a greasy
crayon. In commercial offset lithography, the lithography stone is replaced by
thin metal plate that wraps around a printing cylinder. The imaging areas on the
plate are water repellent and accept ink, while the non-imaging areas accept
water and reject ink. The ink is offset from the metal plate onto a rubber
blanket and then onto the paper, preventing excess wear of the plate. Offset
printing is well-suited for color printing, because a typical press can handle
six colors with a single pass, including four process and two spot colors, or
six-color Hexachrome. WHY WYS IS NOT WYGA common acronym in computer graphics is
WYSIWYG. It stands for "What you see is what you get." Unfortunately, a common
problem in reproducing color graphics is that what you see on the screen is not
what you get when you print. Several effects come together to cause this
Monitors and output devices have limitations. Each device has a
range of colors it can reproduce, called its color gamut. These vary with the
type and model. The printer type, ink and paper quality and the printer's
condition also affect the results.
Equipment can easily become miscalibrated and require very expensive, specialized accessories to keep them
standardized to a predictable performance.3.
Printers that dither can only
create a limited number of colors. If you attempt to print a color which does
not fall within its abilities, it will produce the nearest match. The printer's
resolution is important to its dithering ability, so higher resolution printers
usually print higher quality color. Color management systems are available to
help solve these problems if precise color matching is important to you.