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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Calibration vs. Characterization</title>
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<meta http-equiv="content-type"
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content="text/html; charset=ISO-8859-1">
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<h2 style="text-decoration: underline; font-weight: bold;">Calibration
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vs. Characterization<br>
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Some of the terminology can be confusing. Many people are initially
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confused about the difference between <span style="font-weight: bold;">Calibration</span>
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and <span style="font-weight: bold;">Characterization</span>.<br>
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<h3>What is Calibration ?</h3>
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Calibration is the process of modifying the color behavior of a device.
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This is typically done using two mechanisms:<br>
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1) Changing controls or internal settings that it
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2) Applying curves to its color channels.<br>
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The idea of calibration is to put a device is a defined state with
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regard to its color response. Often this is used as a day to day means
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of maintaining reproducible behavior. Typically calibration will be
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stored in device or systems specific file formats that record the
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device settings and/or per channel calibration curves.<br>
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<h3>What is Characterization ?</h3>
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Characterization (or <span style="font-weight: bold;">profiling</span>)
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is <span style="text-decoration: underline;">recording</span> the way
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reproduces or responds to color. Typically the result is stored in a
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device <span style="font-weight: bold;">ICC</span> profile. Such a
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profile does not in itself modify color in any way. What it does is
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allow a system such as a CMM (Color Management Module) or color aware
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to modify color when combined with another device profile. Only by
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knowing the characteristics of two devices, can a way of transferring
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color from one device representation to another be achieved.<br>
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Note that a characterization (profile) will only be valid for a device
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if it is in the same state of calibration as it was when it was
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<h3>What about display calibration and profiles ?</h3>
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In the case of display profiles there is some additional confusion
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because often the <span style="font-weight: bold;">calibration</span>
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information is stored in the <span style="font-weight: bold;">profile</span>
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for convenience. By convention it is stored in a tag called the 'vcgt'
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tag. Although it is stored in the profile, none of the normal <span
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style="font-weight: bold;">ICC</span> based tools or applications are
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aware of it, or do anything with it, it is just "along for the ride".
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Similarly, typical display calibration tools and applications will not
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be aware of, or do anything with the ICC characterization (profile)
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<title>Calibration vs. Characterization</title>
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<meta http-equiv="content-type" content="text/html;
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<h2 style="text-decoration: underline; font-weight: bold;">Calibration
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Some of the terminology can be confusing. Many people are initially
15
confused about the difference between <span style="font-weight:
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bold;">Calibration</span> and <span style="font-weight: bold;">Characterization</span>.<br>
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<h3>What is Calibration ?</h3>
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"Calibration" is a short hand Graphic Arts term for adjusting a
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devices behavior to meet calibration targets.<br>
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Calibration is the process of modifying the color behavior of a
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device. This is typically done using two mechanisms:<br>
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1) Changing controls or internal settings that it
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2) Applying curves to its color channels.<br>
26
The idea of calibration is to put a device is a defined state with
27
regard to its color response. Often this is used as a day to day
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means of maintaining reproducible behavior. Calibration is often the
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most practical way of setting parameters such as white point and
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brightness of displays. Typically calibration will be stored in
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device or systems specific file formats that record the device
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settings and/or per channel calibration curves.<br>
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<h3>What is Characterization ?</h3>
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Characterization (or <span style="font-weight: bold;">profiling</span>)
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is <span style="text-decoration: underline;">recording</span> the
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way a device reproduces or responds to color. Typically the result
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is stored in a device <span style="font-weight: bold;">ICC</span>
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profile. Such a profile does not in itself modify color in any way.
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What it does is allow a system such as a CMM (Color Management
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Module) or color aware application to modify color when combined
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with another device profile. Only by knowing the characteristics of
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two devices or colorspaces, can a way of transferring color from one
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device representation to another be achieved.<br>
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Note that a characterization (profile) will only be valid for a
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device if it is in the same state of calibration as it was when it
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was characterized.<br>
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<h3>What about display calibration and profiles ?</h3>
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In the case of display profiles there is some additional confusion
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because often the <span style="font-weight: bold;">calibration</span>
51
information is stored in the <span style="font-weight: bold;">profile</span>
52
for convenience. By convention it is stored in a tag called the
53
'vcgt' tag. Although it is stored in the profile, none of the normal
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<span style="font-weight: bold;">ICC</span> based tools or
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applications are aware of it, or do anything with it, it is just
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"along for the ride". Similarly, typical display calibration tools
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and applications will not be aware of, or do anything with the ICC
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characterization (profile) information.<br>
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doc/calvschar.html
