7.5

Monitor display VSPrinting
l The monitor produces the color you see on-screen with light while the printer produces color with pigment. The set of
colors, or gamut, you can produce with light is not identical to the set you can produce with pigment. Thus there are col-
ors you can produce on a monitor and not on a printer, and vice-versa.
l The monitor uses three primary colors of light (red, green, blue) to produce all the colors you see on-screen. It mixes
different amounts of each of the primaries to produce a particular color. An on-screen color is specified as three
numeric values, the first describing the amount of red, the second the amount of green, and the third the amount of
blue light to use to create the color. Thus these are often referred to as RGB (Red Blue Green) colors.
l The printer uses three primary colors of ink (cyan, magenta, yellow) and black to produce all the colors it prints.
l The set of colors you can produce with light (the RGB gamut) is larger than the set of colors you can produce with pig-
ment (the CMYK gamut). Thus monitors can produce more colors than printers.There is a significant overlap between
the two gamuts however, and, in those cases, the problem becomes how to match a color that it is possible to create
with either light or pigment, on different physical devices.
Representation and control of color in physical devices
The difficulty with physical devices is that none are stable enough to ensure a consistent representation of a given color. Phys-
ical devices for our purposes are monitors and printers.
l Monitors The same color can vary across monitors due to factors such as the phosphor specification, the calibration,
and the age of the individual monitor. Even on the same monitor the color can change as the monitor ages or loses its
calibration. The set of colors a monitor can display (its gamut) can also vary across monitors.
l Printers The same color can also vary across printers or on the same printer due to factors such as the inks a printer
uses, the amount of ink in the printer at the time you print, and the physical properties of the paper on which you print.
Colors in PDFFiles
When PDFFiles are used as resources, either external or internal, some optimization is done. A PDF that contains transparent
objects will have the transparency flattened, meaning that the transparent layers will be blended and rasterized.
PlanetPress Suite converts CMYK colours to RGB of all raster images that are not part of a PDF or EPS. It is then preferable to
put CMYK images into a PDF or an EPS since they remain untouched through the entire process to avoid colour shifting at print-
ing time.
Output using PDFresources will differ depending on the type of output used. When printing using a Windows Driver, the output
goes through the Windows GDIengine, and thus is submitted to some color transformations related, especially, to the Win-
dows color profiles. When printing using Printer Centric or Optimized PostScript Stream, these transformations do not occur.
The difference between PostScript printing and GDIoutput can be tested outside of PlanetPress. When using Adobe Acrobat,
the GDIoutput is used by default. However, in the File ->Print dialog, if you click on Advanced Settings and select Print as
Image, Acrobat will then rasterize the image using its own internal RIP, meaning the PDFcolor profile is kept as is. This is
equivalent to printing in a PostScript format.
Color perception
Our perception of a color can change with variations in the ambient lighting. A color that appears very rich under subdued light-
ing may appear washed out under bright lighting. Our perception of a color can also change due to the colors that appear along-
side it. The same color on two different backgrounds can appear to be two different colors. Finally, two individuals may not
see the same color.
To set up color management in PlanetPress Design:
1. Start PlanetPress Design.
2. From the PlanetPress Design Button, choose Preferences to display the Preferences dialog box.
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