How to fix pink/cyan cast in the sky

2011-11-01

A darktable tip.

After recovering highlights in the blown sky (negative exposure correction and/or LCh blending), I often end up with pink or cyan cast in the sky. It looks unnatural. This is an example of the problem:

pink cast in the sky after highlight recovery

A possible quick fix in darktable is to

  • activate color zones plugin
  • choose select by lightness
  • on the saturation tab pull the right end of the curve down

desaturating highlights in color zones plugin

The sky is usually bright and we are used to perceive its highlights as neutral (clouds are “white”, right?). Another aspect: highlights, as well as shadows, appear less saturated to the human eye. So desaturating the highlights looks natural. Most intense (saturated) colors belong to midtones (moderate lightness), and they are not affected. Shadows are not changed either. In general, the colors of the image are mostly left intact.

The limitation of this method seems to be that we cannot use color zones in select by lightness and select by hue modes in the same picture.