'Correction of color data' Dialog

You can open this dialog by clicking "Modify" (paper white correction) in the "Generate profile" dialog > "Show profile options".

Note: In the "Measure" main function, you open this dialog (only the top part) with "Test chart > Correction - Fluorescent whitening".

Check and correct color data

In this dialog, you can correct paper white that is important for certain proofs. You can correct the effect of fluorescent whitening either by automatic paper white correction or by a spectral conversion of the color data. Paper white can also be corrected by matching the lightness of the L value to proof­ing.

Click "OK" to confirm your changes and close the dialog.

When you click "Default", the default settings are restored and the dialog closes.

Click "Cancel" to close the dialog and discard any changes to it. The last setting is restored.

Correction of fluorescent whitening effect

This function is relevant when papers with fluorescent whitening agents are used (for example, paper for color copiers and ink jets). It affects the proof part of the profile.
Optical whiteners have a fluorescent effect so that the paper is perceived as particularly white although technically speaking it has a bluish color cast. If you make a proof based exactly on the val­ues measured, the result will appear too yellow.

Correction can be in two ways:

•using an automatic paper white correction

•or a spectral conversion of the color data.

Change paper white automatically

This function can automatically reduce the effect of fluorescent whitening agents when the proof part is calculated in the profile. By default, this function is disabled. When this function is activated, eval­uation of the proof with a measuring device may produce different results.

Spectral conversion of color data

Spectral color data must be available for this type of correction. In this procedure, all the measured values are corrected before profile calculation. As a result, this correction affects the entire ICC pro­file (all transformation tables).

Fluorescent whitening causes ultraviolet light that cannot be seen by the human eye to be absorbed and visible blue fluorescent light to be emitted in its place. As a result of this conversion, an observer considers the paper to be whiter. But this impression of white is subjective: In Europe, for example, paper is "absolutely white" if the reflected light has somewhat more bluish portions.

You can set the correction intensity (amount of blue) with the slider:

•The default setting (slider position 5) is the equivalent of the spectral effect of a UV filter.

•As you move the slider towards "max" (slider position 10), the bluish color cast is gradually removed by the correction so that the result seems to be yellowish.

•As you move the slider towards "none" (slider position 0), the correction of blue diminishes. There is no correction of the fluorescent whitening effect when the slider is at "none" (0).

Lightness adaption for proof

This function adapts lightness for proofs when papers which are darker than the paper of the simu­lated printing process are used. If a reproduction is based exactly on the values measured, this might impair the light definition and paper white cannot be simulated correctly.

The range of lightness of the proof is increased somewhat so that the lightness required in the print­ing process you want to simulate can fit into the larger range of the proof process. In this way, light definition is retained and media white can be reproduced correctly, but the proof is somewhat darker on the whole. In proofs, slight errors in the reproduction of lightness are generally less disturbing than errors in hue in paper white simulation.

Note: This function should not be enabled if you want a correction of a proof profile (see 'Proof correction' View).

L value

The L* value refers to the lightness of color in the CIELAB color space. In this function, the L* value of paper white in the proof process is shown. To correct lightness, the L* value of paper white of the (lighter) printing process you want to simulate is entered. On the basis of these data, Color Toolbox automatically calculates the lightness correction required for the proof process.
This setting has no effect if a value lower than the L* value of the proof white is entered.