Step 2: Now completely desaturate your Background Copy Layer. By taking the color out, you can avoid oversharpening (and thus worsening) color noise. To desaturate quickly, hit Ctrl (Command on a Mac) + Shift + U on your keyboard.
Note: Photoshop CS3 and CS4 users: If you like, turn your Background Copy layer into a Smart Object before proceeding to Step 3. This will make your High Pass filter into a readjustable Smart filter.