How Calibration Works - Xerox DocuColor 12 Color Manual

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2-3 Understanding calibration

How calibration works

Success in obtaining satisfactory print quality from a color server such as a Fiery
connected to a copier/printer depends on many factors. Among the most important
are establishing and maintaining optimal toner densities. The density is the measure of
the light absorbed by a surface. By carefully regulating toner densities, you can obtain
consistent printed color.
Even with a calibrated system, toner density is affected by service settings, humidity,
and temperature; density also tends to drift over time. Regular measurement detects
day-to-day variations in densities, and calibration corrects for them.
Calibration works by creating calibration curves on the Fiery that compensate for the
difference between actual (measured) and desired (target) density values. These
calibration curves are the graphic equivalent of transfer functions, which are
mathematical descriptions of changes that will be made to the data you start with.
Transfer functions are often graphed as input or output curves.
The Fiery generates calibration curves after comparing measured values to the final
target values for each of the four toner colors. The target values are based on the output
profile specified.
Measurements
Measurement files contain numerical values that correspond to the toner density
produced by the copier/printer when it prints solid cyan, magenta, yellow, and black,
and graduated tints of those colors.
To create a measurement file, first print a page of color patches. Then measure the
patches using either a color measurement instrument connected to a computer on the
network or, if it is available, the print device's scanner. The new measurements are
automatically downloaded to the Fiery.