Correcting the White and Black Point
This tool allows to adapt the paper white with the White Correction and the darkest color with the Black Correction sections respectively.
The tool White Correction allows to apply manual corrections to the whitest color patch of the measurement data which is typically the paper or substrate color. The tool is to be used on a single measurement files. The correction in form of a modified Lab or LCh input value is helpful in such circumstances where either a certain target white point shall be reached or corrections are needed to lighten, darken or recolor the file. The manual correction is then applied to the entire measurement data keeping the print characteristic intact.
White Correction: predicts the impact of the paperwhite changes to the measured values of a test chart. With ColorAnt you are able to use three different methods to calculate this effect; ColorLogic Default, ISO 13655 and Relative Colorimetric.
White Correction Methods
ColorLogic Default: uses a spectral color model to apply corrections leading to the most realistic results. This works best if both the data that should be changed and the white picked from another file are spectral data. When no spectral data is available, ColorLogic Default proceeds like ISO 13655 and assumes that the shadows are not affected and that there is a much lower impact on the primary colors.
ISO 13655: similar in the highlights and colorful primary colors to relative colorimetry. However, this method assumes that the shadows and very dark colors are not changed.
Relative colorimetric: paperwhite changes will modify the entire color space. In cases of major changes in the paper white this will also strongly affect primary colors.
Black Correction: users can change the darkest black which will scale the entire data set toward the edited black point. Useful in situations where black has been measured to dark or to light compared to the visual appearance. Common scenarios include materials used in industrial applications like ceramics, textile, glass etc. Important: Black Correction is not available when using the Relative Colorimetric Method.
Procedure for White Correction:
- Load the measurement data that you want to change and the data containing measurements of the new paperwhite.
- Click on White/Black Correction
- Choose to adjust the corrections in LCh or Lab Color Mode. Change the mode at any time. LCh allows to adjust the hue or chroma independently whereas corrections in a* and b* will change hue and chroma simultaneous. The splitted color patch displays the original white on the left side and the modified white on the right side.
- Either manually edit the desired white point with the slider or by typing in Lab numbers or pick the new white point from the other data file using the eyedropper icon. Click on the eyedropper and select the other data file to automatically pick the new white point.
Note: The eyedropper will pick the whites patch from the selected file. If spectral data is detected, the tool will use it according to the Method selected.
- Note: The sliders allow for small changes. More precise numbers can be entered in dialog. The sliders will reset after.
- When changing the Lightness (L* value) and using the Method Relative Colorimetric typically the darkest colors of your measurement files will be affected, too. If you want the black point and the darkest colors to not be affected, use the Method ISO 13655. Both methods, relative colorimetric and ISO 13655, apply calculations with colorimetric data. Only the ColorLogic Default, which is the default setting, will use the full spectral data and a spectral model for the calculation.
Note: Depending on the color difference of the paper white and if optical brightener agents are available this can affect primary colors.
- Clicking the Reset button will discard your slider modifications.
- Clicking the Start button will apply your changes on the entire measurement file. The dialog will close automatically after calculation.
Procedure for Black Correction:
- Load measurement data.
- Click on White/Black Correction.
- Select either ColorLogic Default or ISO 13655.
Note: Relative colorimetric does not allow changes to the black point.
- Adjust the correction in LCh or Lab Color Mode. LCh allows adjustment of the hue or chroma independently whereas corrections in a* and b* will change hue and chroma simultaneous. The split color patch displays the original black on the left side and the modified black on the right side.
- Either manually edit the desired white point with the slider or enter the Lab/LCh numbers.
- Click the Reset button to discard the slider modifications.
- Click Start to apply the corrections. The dialog will close automatically after calculation.