Preventing Over-Saturation
A Technique Using a Saturation Mask
Increasing a images color saturation can have very pleasing results and can be a handy step in Black & White conversion for a more drastic effect. However, there are times when a part of an image may already have fairly bold color and adding further saturation can cause a loss in image quality. For example, the subject may have good saturation, but other elements of the image my not have quite the “punch” you wish them to have.
This is where the Saturation Mask comes into play. The Saturation Mask is a mask that will only select the most saturated parts of an image. By inverting this mask, we can then safely increase the images saturation without over-saturating the already bold colors.
Note: If you have an image that is starting off with overall low-saturation, this may not benefit you too much (or at all).
Creating the Saturation Mask
Duplicate the background layer: Select it and press Command+J- Rename it to “Color” and set the blending mode to Color
- Create a new layer below the “Color” layer called “Mask” by holding down Alt and clicking on the “Create new layer” button at the bottom of the Layers Pallet
- Create a new layer above the “Mask” layer called “Source”
- Set the Foreground Color to 50% Gray (RGB value of 128, 128, 128 or hexadecimal value of #808080)
- Fill the “Source” and “Mask” layers with the gray: Select each and press Option+Backspace
Your Layers Pallet should look like the example to the right. - Select the “Color” layer and merge it with the “Source” layer: Command+E
- Change the blending mode of the “Source” layer to Difference
- Merge the “Source” layer down with the “Mask” layer
- Desaturate the “Mask” layer: Command+Shift+U
Bring up Curves (Command+M) and click on the top-right end of the Curves Line. Set the input value to 128 and hit OK
- What you see wile adjusting Curves is what will shortly become your Saturation Mask. White represents the most saturated portions of the image with black being the least saturated. With a little bit of practice you can easily use Curves to tweak the intensity of the Saturation mask to your liking.
- With the “Mask” layer selected go to the Channels Pallet
- At the bottom of the Channels Pallet click on the “Load channel as selection” button
- Click on the “Save selection as channel” button (Select » Save Selection…) and name it “Saturation Mask”
- Now you have a Saturation Mask at your disposal for whenever you need it. Simply hold down Command and click on it to load it.
- Delete the “Mask” layer. There is no need to keep it since you now have the mask saved as an Alpha Channel
Put it to Use
Now that you have a Saturation Mask, it’s time to use it.
- Load the Saturation Mask: Command+Left-Click it
- Since we don’t want to saturate the already highly saturated parts of the image the mask needs to be inverted: Command+Shift+I
- Create a new Hue/Saturation Adj. Layer (Layer » New Adjustment Layer » Hue/Saturation…) or a Channel Mixer Adj. layer (as outlined in my Adjusting Color Saturation tutorial) to adjust color saturation
The new Adjustment Layer will apply the mask to it’s Layer Mask only allowing adjustments to the parts of the image with lesser amounts of saturation.
Examples
These test images are based off an original image created with 70% saturation (AdobeRGB color space). Notice how the use of the saturation mask allowed the increase of saturation without the center area becoming over-saturated.
Actions
Actions for this tutorial can be found on the Downloads page.