How to Desaturate Shadows in Photoshop, for 3D Contrast

Digital capture technology is really awesome and has truly changed photography, improving it in a multitude of ways. But sometimes, digitally captured images have a certain exaggerated colorfulness, that just looks a little off, for those of us raised on the old fashioned film days! I have found that this has to do with the way color gets saturated as contrast increases. Even standard rendering presets increase contrast a bit through a global RGB composite curve, often indirectly. It seems that when contrast increases this way a global increase in saturation results that increases the chroma, or colorfulness, evenly throughout the image. This makes shadow values unrealistically colorful. Our natural perception of color decreases with reduced light, such that, as a shadow approaches black, color saturation is gradually reduced to zero. If you can correct for the tendency to increase color in the shadows as contrast is increased, you can achieve a more natural sense of contest and 3D shape in the image.

Lets take a look using the following example:

Shadows Too Colorful

The RGB values in the arm, right before it goes to zero black is 31, 1, 1 – way too colorful for a shadow this dark!

Looking at the deep shadow at her right arm, we can see a subtle region of exaggerated color in the deep shadow. Reading the RGB values confirms this—the reading of 31,1,1 is unrealistically colorful—we can see a sort of band of extra deep color right next to the black shadow. This is the bane of digital capture, in my humble opinion! Lets see what happens when we fix this.

Start by selecting solid gray color from the adjustment layer icon at the bottom of the Layers panel – this type of layer is not available from the Adjustments panel, so you have to get it here!

Solid Color Fill

Make a Solid Color Layer and select a neutral gray in the resulting dialog!

Gray color picker

Make sure Saturation is zero for the gray layer

The idea is to use this gray color to desaturate the underlying layers selectively – right now the solid gray covers up the whole image!

Solid Gray

The new Solid Color layer covers up everything!

Now we will use Blending Options to change how this gray interacts with the image – select Blending Options from the layer options flyaway menu at the upper right corner of the Layers panel.

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