Modify a photo via blend modes

Step 1 - Open the photo
If it isn't already open, open the photo you wish to modify. Also, make sure the Layer palette is displayed.
Step 2 - Duplicate the Background layer
In the Layer palette, click the Duplicate Layer button. This creates a layer named Copy of Background. You'll be modifying this layer.
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Step 3 - Set Blend Mode to Overlay
On the duplicated layer, click the Blend Mode drop down button (the current blend mode should be Normal), and choose Overlay.
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Step 4 - Adjust layer transparency
Adjust the duplicated layer's transparency setting from 100 to a value below 50 percent. For most photos, you'll get the best results between 20 and 40 percent. Select this step's script to set this value to 30 percent.
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*Optional* Step 5 - Toggle visibility on and off
*Optional: To see the effect on the photo, click the duplicated layer's Toggle Visibility icon on and off.
Notes and Tips:
The Overlay blend mode tends to help produce more vivid colors. Experiment with other blend modes to create interesting effects.

Learn More:
Fix a photo
Create soft focus - Method 1
Create soft focus - Method 2