Ricoh InfoPrint Pro C900AFP Manual page 243

Each device has its own individual color space and range of colors that it can
display or print. The color space specifies how color information is represented in
an image when it is displayed on a particular device. As the image is passed from
one device to the next, the color information about the image is converted from the
color space of the source device to the color space of the destination device.
Because color spaces do not exactly match between devices, some of the color
information can be lost or modified in the conversion process.
A color space is a representation of the individual colors that can be combined to
create other colors. Some color spaces that are relevant to printing are:
v RGB
In an RGB color space, red, green, and blue light are combined in different
amounts and intensities to create different colors. RGB colors are often specified
as single-byte integers numbered from 0 through 255. You can specify 256 levels
of intensity for each of the three colors. For example:
– R=0, G=0, B=0 yields black
– R=255, G=255, B=255 yields white
– R=251 , G=254 , B=141 yields a pale yellow
– R=210, G=154, B=241 yields a light purple
Devices such as monitors, digital cameras, and scanners generally use RGB color
spaces to describe colors. Two standard implementations of RGB color spaces are
sRGB, which is most often used for Web graphics, and Adobe
which we recommend for graphics that are printed.
v CMYK
In a CMYK color space, cyan (bright blue), magenta (bright red-pink), yellow,
and black pigments are combined to create different colors. CMYK values are
often represented as a percentage. The percentage represents the portion of a
particular area of paper that is covered by ink or toner. For example:
– C=0%, M=0%, Y=0%, K=100% yields black
– C=0%, M=0%, Y=0%, K=0% yields a blank area on the page
– C=1.6%, M=0%, Y=44.7%, K=.4% yields a pale yellow
– C=17.6%, M=39.6%, Y=5.5%, K=5.5% yields a light purple
Color printers use the CMYK color space; they are loaded with ink or toner in
each color. When the printer places dots of the correct sizes next to and on top
of each other on a page, your eye interprets them as the intended color.
Implementations of the CMYK color space vary from printer to printer and from
paper to paper. Because the original color space of most images is an RGB color
space, it is best to leave images in an RGB color space so they retain their
original characteristics. That way, your print server or printer has as much of the
original color information as possible when it converts the images to the most
appropriate CMYK color space for the printer and paper combination.
If you save an image by using the CMYK color space, make sure that you either
save an ICC profile for that color space or use a standard non-device specific
CMYK color space like SWOP or Coated FOGRA27 and associate the
appropriate ICC profile with the image.
Note: Both RGB and CMYK values can be expressed in different ways. For
example, in the PostScript data stream, the values range from 0.0 to 1.0, while in
some graphic arts programs they can be expressed in hexadecimal numbers or as
percentages.
Chapter 25. Color and grayscale printing using AFP
®
RGB (1998),
225