Step 1 : Open an image of your choice in photoshop
Step 2 : now duplicate the layer
Step 3 : go to filter>blur>gaussian blur and set the radius a high number. I set mine to 10.0 pixels.
Step 4: now you can adjust the opacity of the duplicated layer till you are happy with the effect. You can also go to the layers blending options and play around with different blend modes. In the below image the opacity is set to 60%.
More Tutorials: 
