Creating Printer Profiles: Measurement Processing

When creating or updating printer profiles it may be necessary to optimize the measurement data. The Measurement Processing in CoPrA includes the optical Brightener Compensation, the Measurement Correction and the specification of a Viewing Condition.

Brightener Compensation: For bright white papers that contain optical brighteners it is recommended to run a brightener compensation. This correction weakens the effect of optical brighteners, which are evaluated differently by a measuring device compared to the human eye, and prevents negative accompanying effects such as a yellowish color reproduction.

Recommendation: Work with spectral measurement data whenever possible. If you work with spectral measurement data, the function Brightener Compensation can achieve an optimum correction for papers containing optical brighteners. The correction will only be executed – in contrast to colorimetric measurement data (Lab measurement data) – if CoPrA recognizes the paper color as optical brightener. However, it will not be carried out if CoPrA does not recognize the paper color as optical brightener, which, for example, is true for a blue-colored paper.

As a result of the viewing condition changes according to ISO 3664:2009, optical brighteners in papers are excited more intensively, so a small correction is necessary for measuring devices using the M0 measuring method as well.

 


Note: If you would like to specifically correct the effects of optical brighteners, use the measurement data optimization program ColorAnt before profile creation in CoPrA. In that case please disable the corresponding checkbox in CoPrA to avoid double compensation.

Measurement Correction: The intention of the measurement correction is to identify and resolve measurement errors, without changing the printing behavior. Redundant measurement values, which occur in typical test charts such as ECI2002 or IT8.7/4, are taken into consideration for detecting consistent printing properties and will be intelligently included in the correction. Further corrections, like removal of redundant measurement values or smoothing, can be done in the separate measurement data processing program ColorAnt.
Recommendation: For your own measurement data select Measurement Correction as default setting. However, you should disable this correction for measurement values that have already been smoothed (such as FOGRA measurement values).

Viewing Condition: Typically, printer profiles are optimized for D50 viewing conditions. However, for different tasks, e.g. photos in a gallery under incandescent light (roughly corresponds to viewing condition A) or monitor displays under a trade fair lighting with suboptimal lighting conditions (e.g. fluorescent light), you can take lighting conditions into account when creating the profile.
To do so select one of the three predefined viewing conditions or manually enter the measured viewing condition as Kelvin value or even better as XYZ value.
Alternatively, you can simply drag and drop a measurement file (TXT or CSV file) of the measured light onto the value field. CoPrA then extracts the white point from the file and displays the value. CoPrA then uses this information to calculate a printer profile that makes your prints (with the selected viewing condition) appear in the same way as they would under the standard D50 viewing condition. In contrast to other solutions spectral measurement data are not required.

If you are using spectral measurement data of a test chart and a spectral light measurement of a viewing condition, CoPrA will use a spectral color model rather then the usual chromatic adaptation according to CIECAM02. Chromatic adaptation according to CIECAM02 will only be used if you do not provide spectral light measurements as viewing condition and/or if the test chart does not contain spectral measurement values. To select a spectral light measurement select the entry Emission in the drop-down menu Viewing Condition and then select your measurement data file in the subsequent dialog or just drag and drop your measurement data file onto the drop-down menu.
Note: CoPrA remembers the last used settings including the selected Viewing Condition. If you create new profiles, please check whether the selected viewing condition is in accordance with the purpose of the profile. If no specific viewing condition is required always select the default D50.

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