The steps below summarize the two-pass sharpening technique described in "Out of Gamut: A Two-Pass Approach to Sharpening in Photoshop."

STEP 1: Sharpen to Correct the Image

CREATE EDGE MASK

• Duplicate your image, using Image>Duplicate... and leaving the original image open

• Convert the duplicate to grayscale (duplicating one of the color channels using the Channels palette often works well)
• Isolate the edges using Filters>Stylize>Find Edges
• Apply a Gaussian Blur to soften edges and reduce noise
• Invert the mask, by choosing Image>Adjust>Invert
• Exaggerate the contrast of the mask using Image>Adjust>Levels

APPLY EDGE MASK

• Make the original image active, by selecting it from the Window menu.

• Load the edge mask into the image by choosing Select>Load Selection and making sure the name of your duplicate file is entered as the source document

SHARPEN EDGES

• Press Command-H (Mac) or Control-H (Windows) to hide the selection outline

• Sharpen the selection defined by the mask using Filter>Sharpen>Unsharp Mask...
• Press Command-H (Mac) or Control-H (Windows) to restore selection outline (to avoid unintentionally acting only on the selection again)

Step 2: Sharpen for the Output Device

• If necessary, use Select>Deselect to turn off edge-mask selection

• Sharpen as appropriate for your output device