Here’s a quick tip for taming saturation when adjusting contrast in Photoshop. In the example below I’ve added a Curves Adjustment layer and made an edit at the quarter tones – your typical contrast ‘S’ bend. The left side is masked to show the original uncorrected.
Whilst the contrast in the image has improved we’ve also introduced an issue with the saturation. This is because adjustments such as Levels and Curves affect tones so have an impact on both lightness and colour when working with colour images.
If we increase or decrease tonal values in a neutral grey it gets lighter or darker. The same adjustment on anything other than neutral greys will change the ratio or balance of the colour values which leads to colours becoming over-saturated when making strong ‘contrast’ changes.
Fortunately there’s a simple, one-click, remedy we can apply so that our contrast adjustment only affects the lightness in our image. Change the Blend Mode of our adjustment layer to Luminosity.
Now the Lightness values from our adjustment are blended and the colour changes are ignored so we get control of the contrast without introducing saturation issues.
As a final parting tip try changing the layer Blend Mode to ‘Color’ and you’ll get control over the colour without affecting contrast.