- Under the Image Menu choose Mode, and select Lab Colour
- Under the Image Menu choose Apply Image. The Apply Image dialogue appears. It is set by default to Multiply.
- Change the Blending pop-up menu to Overlay (Soft Light also gives a good result).
- On the Channel pop-up menu it is set by default to Lab, click on the tab and try a, and b to see which one gives the best result.
- You can also use the Opacity slider to lessen the effect.
- When happy under Image Menu choose RGB.
The after image (on the right below) was treated using the above steps. The settings used are shown in the settings image.