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Dan Rodney/3 min read

Creating Masks with Calculations

Common Photoshop Tools

Brush Tool

Paint with custom brushes, opacity, and flow control.

Clone Stamp

Sample one area and paint it elsewhere — perfect for repairs.

Healing Brush

Smarter than clone — blends texture and tone of the source.

Pen Tool

Create precise vector paths for selections or shapes.

Master Photoshop at Noble Desktop

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Learn how to correctly fix over-saturation in images using the Calculations command and Hue/Saturation adjustments in Photoshop with this comprehensive tutorial.

Topics Covered in This Photoshop Tutorial:

Fixing Over-saturation, the Calculations Command, Applying Hue/Saturation Only to Over-saturated Areas

Exercise Preview

boxer done

Exercise Overview

The image’s oversaturated colors look wonderful on-screen but will never print as we see them, so we need to desaturate. However, we do not want to desaturate the image overall. Doing so would wash out the image and produce a different effect from what we are after.

So how do we go about selecting the most saturated parts of the image? We could perform color ranges on various parts of the image, but this would be time-consuming and would yield imperfect results. Duplicating color channels would not work because the whites and grays would then also be selected. Instead, let’s try the power of the Calculations command.

  1. If you have any files open, close them now.

  2. From the Photoshop Adv Class folder, open the file boxer.jpg.

  3. If you get a message about a missing profile, choose Use the embedded profile and click OK.

  4. Go to Image > Calculations. Do not click OK until we say so.

  5. Under Source 1 make sure the menu reads boxer.jpg, then set the following:

    Layer: Background
    Channel: Red
    Invert: Leave it unchecked

  6. Source 2 should also be set to boxer.jpg. Set the following:

    Layer: Background
    Channel: Blue
    Invert: Leave it unchecked

  7. Set the rest of the options as follows:

    Blending: Difference
    Opacity: 100%
    Mask: Leave it unchecked
    Result: New Channel

    Why Did We Choose That?

    We chose Difference because Photoshop isolates areas in the channels that differ and creates a mask based upon those differences. Vibrant colors differ radically between channels while whites, grays, and blacks are virtually the same from channel to channel.

  8. Click OK.

  9. Switch back to the composite RGB by pressing Cmd–2 (Mac) or CTRL–2 (Windows).

  10. Duplicate the image (Image > Duplicate). Then click OK.

  11. Choose Window > Arrange > 2-up Vertical to put the two side-by-side on-screen.

  12. In the new duplicate image, create a new Hue/Saturation adjustment layer and set Saturation to −40. Note the “washed out” look.

  13. In the original image, in the Channels panel, Cmd–click (Mac) or CTRL–click (Windows) on the new alpha channel (Alpha 1) to load it as a selection.

  14. If the new alpha channel is visible, hide it before continuing.

  15. Select the Inverse (Cmd–Shift–I (Mac) or CTRL–Shift–I (Windows)).

  16. Create a new Hue/Saturation adjustment layer.

  17. Set Saturation to −40.

  18. Note how the image is desaturated only in those areas that were oversaturated to begin with. The skin tones are one area where you can especially see this.