In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run.
The widely-spread offset printing process is composed of four spot colors:
Cyan, Magenta, Yellow and
Key (black) commonly referred to as CMYK. More advanced
processes involve the use of six spot colors (hexachromatic process), which add Orange
and Green to the process (termed CMYKOG). The two additional spot colors are added to compensate
for the inefficient reproduction of faint tints using CMYK colors only. However, offset
technicians around the world use the term spot color to mean any color generated by a non-standard offset ink; such as
metallic, fluorescent, spot varnish, or custom hand-mixed
inks.
When making a multi-color print with a spot color process, every spot color needs its own lithographic film. All the areas of the same spot color are printed using the same film, hence, using the
same lithographic plate. The dot gain, hence the
screen angle and line frequency, of a spot color vary
according to its intended purpose. Spot lamination and UV coatings are sometimes referred to as
'spot colors', as they share the characteristics of requiring a separate lithographic film and print run.
Computer methods
There are various methods to incorporate rather sophisticated patterns of spot colors in the final prepress artwork. Software applications such as Adobe InDesign,
Adobe Illustrator, QuarkXPress and
Scribus may generate spot colors as additional channels. Adobe
Photoshop can also be used to generate soft edges (widely known as feathered edges) of spot colors. The dissolve effect
provided by Adobe Photoshop layer patterns can be generated for any spot color.
Optimizing usage
Generally the cost and potential for problems for a print job increase as you add more spot colors, due to the increased cost
and complexity of added process inks and films, and requiring more runs per finished print. However, spot colors can be a very
powerful weapon in security printing, like money, passports,
bonds, and other similar prints that should be hard to forge. Money printing for example, uses secret formulae of spot colors,
some of which can be seen by the naked eye, and some cannot be seen unless by using special lights, or by applying certain
chemicals.
Digitization
Spot colors are now a great business for a company like Pantone. The modern trend in spot color matching systems is the
digitization of spot colors. This idea came from the fact that a spot color print won't be a match to the monitor's colors, due
to the inherent differences in printed (ink) colors and monitor (light) colors. To achieve a rather good result of simulating the
RGB colors into CMYK colors in offset prints, a proper monitor calibration should be done to
realize a good balance between reproduction of gray color on paper and on screen.
Classification
Spot color classification has led to hundreds of discrete colors being given unique names. There are several industry
standards in the classification of spot color systems, such as:
Because each color system creates their own colors from scratch, spot colors from one system may be impossible to find within
the library of another.
See also
- CMYK color space
- color
- color printing
- four-color printing
- printing
- Process color
- Spreading and choking
External links
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