Smart Saturation

I have been looking around GIMP plugins for a smart way to increase saturation without the overly processed and unrealistic look. The problem, I concluded, is that the saturation tool in GIMP doesn't distinguish between light and dark areas of a picture, and often the dark areas of the picture are too saturated to give a natural look. This problem can easily be avoided by using a layer mask which filters the saturation effect depending on the luminosity. Sounds interesting? Please read on...

Step 1: Open up your image in GIMP. And start by duplicating the Background layer. In the picture below I have renamed the layer Saturation.

Duplication of Background layer.

Step 2: Select the top layer (named Saturation in this example), right click on it and choose Add layer mask... In the dialog that pops up, choose Greyscale copy of layer, and click Add. Now you should have a bottom layer (Background in this example), a top layer (Saturation) and its layer mask (to the right).

Top layer selected (white border).

Step 3: Select the top layer by clicking on it. As you click the layer you notice a white border around it (see above image), which tells you it is selected.

Step 4: Go to Colors > Hue-Saturation... and play around with the Saturation slider until you get a result you are happy with. Here is my example without the layer mask (to the left) and with the layer mask (to the right).

Saturation without layer mask

Saturation with layer mask.