User's Manual Part 1

which can make individual dots more observable and subject to moiré pattern generation. With
Dye Sublimation, users achieve essentially the continuous-tone quality of photographs.
Moiré patterns can become a factor when users generate either print files or hard copy
separations for offset printing. Users should ask the people that do their offset printing which
separation angles best reduce these patterns before risking a distorted result. Many applications
offer Print dialog options for these settings.
All the non Dye Sublimation print methods work because people perceive individual dot colors
only to the point the dots remain individually discernible. At sizes or distances where individual
dots cannot be seen, optical mixing occurs. To see individual dot intensities or colors, view the
monitor or printed page using an eye loupe or other such magnifier. Not all images require high
dot densities. The need for high dot density decreases as the viewing distance increases. For
example, a large roadside sign may require separations screened at only four lines-per-inch.
Note that press men use lines per inch, because of the screens used to vary dot size, and
computer users use dots per inch, but both refer to picture resolution.
Because a monitor and a printer produce color using different methods, users can expect
somewhat different results. A monitor uses an additive process, meaning a particular color
derives from intensity control. For example, a color moves toward the green by intensifying
excitation of green phosphors. Printed images, on the other hand, use a subtractive process.
These images display their color through reflected light—unlike monitors, which become a light
source created by excitation of phosphors. To create a particular printed color, the process must
subtract (that is, filter out and not reflect) the spectrum parts of the source illumination that do
not contribute to the color desired.
The light reflected off of the surface of a white card passes through the colored dyes deposited on
the surface of the card, both going and coming. The dyes used to form printed images serve as
filters of light that would otherwise reflect off of what is typically a white print media. In printed
images, complete filtration (or what serves as the maximum subtraction capability), results in
black. The absence of filtration results in the media color. In monitors, maximum beam
intensities (maximum additions) result in white, and minimum intensities produce black.
Because light reflected from print media depends on ambient lighting, users may get darker
images from a printer than they see on a monitor, particularly a monitor with a high intensity
setting.
Print illumination (generally from room or outdoor lighting) affects color for all printed images.
When a light source emits less in certain parts of the visual spectrum, a print illuminated by this
source by necessity reflects less of the associated colors. This is true even though the
corresponding light reflecting capability remains inherent in the print. Imagine, for example, the
effect of placing a color filter in front of a light source. Only the visual spectrum parts passed by
this filter reaches the print. Viewers can sometimes see subtle effects of this by observing the
same print under sunlight, incandescent lights, and fluorescent lights.
Sunlight radiates fairly evenly over the entire visual spectrum, having only a slight increase at the
center. Incandescent lights radiate far more on the red side than on the blue side of the visual
spectrum. Fluorescent lights radiate differently depending on their phosphor blends. Such
classifications as “Cool Light” and “Warm Light” refer to blue-rich and red-rich enhancements,
respectively.
980286-001 Rev. A 3-3
CHAPTER 3
THEORY OF OPERATION