High Frequency Separation (Or the perfect way to retouch skin on Photoshop)

Been a while since I did a tutorial and I have been doing a lot of editing recently so I thought I might share since a few of my old tutorials are terrible.

So this is my original image taken as part of a fashion shoot that I did for some fashion management students and the final edit that I did as part of my Advanced Image Editing class.

1. Open the image in Photoshop. If it is a RAW file, tweak it to how you want it to look. 
2. Duplicate the original layer twice
   
3. Select the middle layer and go to Filter>Blur>Gaussian Blur...
4. Using the Blur filter, zoom in on an eye and set the blur so the eye is just able to make out. 
   
5. Close the filter once you are satisfied with it. and select the top layer.
6. Go to Image>Apply Image... This will open up a window with a few options.
7. In the Apply Image menu, select the middle layer in the Layer drop down menu. 
   
8. Set the Blending to Subtract
9. Set the Scale to 2 and the Offset to 128.
10. Close the Window and set the top layer's blending mode to Linear Light.
    
11. This will have separated the colours and the detail within the image. Select the middle layer again and apply a Quick Mask by pressing Q and using the paintbrush to paint over the areas you want to edit. 
    
12. Press Q again to exit the Quick Mask and then Ctrl + Shift + I to invert the selection and apply a Gaussian Blur to the selection. 
    
13. Then select the top layer and you will be able to sort any blemishes using the Spot Healing  Brush Tool or the Healing Brush Tool (see here for a slightly in-depth tutorial on them)

And that should be you finished the skin retouching :)