| SPECTRAVIEW II - USER’S GUIDE
3
Calibration Overview
Introduction to display monitor calibration
Computer display monitors display images by giving off light from the screen. On LCD display monitors, light is
emitted from a backlight source such as fluorescent lamps or array of LEDs (Light Emitting Diodes) and passes
through individual red, green and blue filters for each pixel on the screen.
Combining red, green, and blue light, known as additive primary colors, creates the color that appears as an image
on the screen. Different colors are displayed by varying the relative brightness of the three additive primary colors.
The range of colors that can be represented on a display is known as the color gamut.
Printers create images by applying inks or dyes known as colorants to paper. These colorants absorb or subtract
light of certain wavelengths, stopping it from being reflected. Cyan, magenta, and yellow colorants, known as
subtractive primary colors, are used to create color prints. Each colorant absorbs light of its color complement.
For example, magenta ink absorbs green light, while cyan ink absorbs red light, and yellow ink absorbs blue light.
Sometimes an additional black colorant is used to improve the overall color gamut possible with a printer.
It is because of these fundamental differences between displaying an image on a computer display monitor and
printed media that a Color Management System such as Apple ColorSync or Microsoft Image Color Management
and a color calibrated display monitor are necessary. The Color Management System ensures that what is displayed
on a monitor, is representative of what will be printed.
In order to accurately view and exchange images with others with confidence that the images look identical when
displayed on different systems and at different locations, the display monitors used should be calibrated to a known
state. The Color Management System being used must also know the current state of the monitor so that it can
determine how to accurately display images on that particular monitor.
Once the display has been calibrated and the Color Management System knows the color characteristics (via the
use of the ICC/ColorSync monitor profile), the display can be used to preview or soft proof what images will look like
when printed. In order to do this, the Color Management System must also know the color printing characteristics
of the printer being used. This is usually done by an ICC printer profile or Printer Color Separation Tables supplied
by either the printer manufacturer or a third party. Various desktop publishing and image editing software packages,
such as Adobe Photoshop, have CMYK preview modes to soft proof images.
It is important to be aware of the limitations of soft proofing. Many factors will limit the accuracy to which prints will
match what is displayed on the screen. The accuracy of the printer profile or color separation tables as well as the
type of inks and paper used all affect how accurate the final prints will be. The lighting conditions used when viewing
the final print is also absolutely critical and the use of a calibrated lightbox is highly recommended. Be aware that
it is almost impossible to get an absolute perfect match under all conditions on any color management system or
display.
Before calibrating the SpectraView display, the desired color characteristics of the calibrated monitor must be
selected. In SpectraView, these characteristics are called Targets. SpectraView then adjusts the monitor to the
color characteristics in the selected Target. Once the calibration is complete, SpectraView can then re-measure
the display and create an ICC/ColorSync profile of the monitor, which contains information used by the Color
Management System to retain the various color characteristics of the calibrated monitor. The calibration target used
will depend on the application.