Manual Color Calibration

Warning

The color calibration must be performed on a linear image whose histogram has not yet been stretched. Otherwise, the colors obtained are not guaranteed to be correct.

The manual way uses the following window:

dialog

Manual Color Calibration dialog window.

The first step deals with the background of your image. The goal is to equalize the RGB layers in order the background appears as a neutral grey color.

After making a selection in your image (in a not so crowdy nor contrasted area), the area is taken into account by clicking on the Use current selection button. The coordinates of the rectangle are displayed. Then Background Neutralization will calculate the median of each channel and equalize them.

The second step deals with the bright objetcs of the picture. You can modify once again the histogram in two ways:

  • Manually, with White reference and the 3 R, G and B coefficients, according to your own taste.

  • Automatically, by selecting a rectangle area with contrasted objects (the same way as previously)

Two sliders allow you to change the rejection limit for too dark and too bright pixels in the selection.

As this is a trial and error process, you can undo the result with the Undo button (up left) and then try with other selections or coefficients until you are satisfied.