Some of the terminology can be confusing. Many people are initially
confused about the difference between Calibration and Characterization.
What is Calibration ?
"Calibration" is a short hand Graphic Arts term for adjusting a
devices behavior to meet calibration targets.
Calibration is the process of modifying the color behavior of a
device. This is typically done using two mechanisms:
1) Changing controls or internal settings that it
2) Applying curves to its color channels.
The idea of calibration is to put a device is a defined state with
regard to its color response. Often this is used as a day to day
means of maintaining reproducible behavior. Calibration is often the
most practical way of setting parameters such as white point and
brightness of displays. Typically calibration will be stored in
device or systems specific file formats that record the device
settings and/or per channel calibration curves.
What is Characterization ?
Characterization (or profiling)
is recording the
way a device reproduces or responds to color. Typically the result
is stored in a device ICC
profile. Such a profile does not in itself modify color in any way.
What it does is allow a system such as a CMM (Color Management
Module) or color aware application to modify color when combined
with another device profile. Only by knowing the characteristics of
two devices or colorspaces, can a way of transferring color from one
device representation to another be achieved.
Note that a characterization (profile) will only be valid for a
device if it is in the same state of calibration as it was when it
What about display calibration and profiles ?
In the case of display profiles there is some additional confusion
because often the calibration
information is stored in the profile
for convenience. By convention it is stored in a tag called the
'vcgt' tag. Although it is stored in the profile, none of the normal
ICC based tools or
applications are aware of it, or do anything with it, it is just
"along for the ride". Similarly, typical display calibration tools
and applications will not be aware of, or do anything with the ICC
characterization (profile) information.