Lab Color Mode Saturation

The Lab color mode for images can be used to increase (or decrease) the saturation.

Open your image.

Change the image's color mode to Lab using Image > Mode > Lab Color. If you want to compare the changes to the original image make a copy and perform the following steps on the copy. Then you can switch back and forth between copy and original by alt-clicking on the original image's layer visibility icon.

Open the Curves tool with Ctrl-M

Change the Channel to a

Apply a double curve like this:

Change the channel to b and apply the same curve. Click OK to accept the change.

Merge and save if you duplicated the layer, or simply save the image.

The input values have been adjusted by 10 brightness units in the above example. You can try different values to see if that's better for your image.

If you want to use the same curve as in the above diagram, you can download it by right-clicking this LINK and choosing "Save Link As..." Save it to the Presets/Curves folder in your Adobe Installation folder.

It's worth understanding why this works. The Lab color model is named for its three channels, L (lightness), a (red-green) and b (blue-yellow). Lab color is an alternative color mapping designed to better represent how human eyes perceive color in terms of opposites. In most of your images you'll find that the a and b channels are sharply peaked at mid-histogram, indicating that most of the pixels are fairly close to being balanced in both a and b color space. The double curve serves to stretch pixels away from the histogram center in both directions, intensifying their imbalance and making colors more vibrant.

You can also use the Lightness channel to change brightness and contrast, but that's not as easy to control.

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