Image processing - doubling frequency?

Question

There's some image processing commands in photoshop, like high pass and blur (i.e. low pass). I want more. Is there a way to achieve frequency doubling, or better yet, frequency x N where N is any number the user can specify?
This may be useful for making coarse skin texture look finer. It can be implemented by diving the selected area into small squares, and then shrink each squares to half their original sizes. This would make the details look finer grain (hence frequency doubling). It would open up gaps between the squares, which can be filled in by taking additional samples and shrinking them to fill the gaps. This is similar to frequency doubling in audio processing.
I'm using cs4 extended. Is there an add-on to do this?

Answer 1

Yes there is a retouching method that uses "so called" high frequency and low frequency layers. There is a great discussion in the retouching section on a site called Model Mayhem. Some pretty clever retouchers hang out there. You can use this effect to smooth skin for portraits, and you can vary the smooting from just a small amount to some of the images used in makeup advertising where the model has a perfect yet sort of plastic looking skin. I use this technique now and again working on portrait subjects that have less than perfect skin.
Basically you make two copies of your opening layer, name the first layer "Low Frequency" and the second layer "High Frequency".
Select the Low Frequency Layer and apply a small amount of Gaussian Blur around 2.9 is a good starting point
Now go to the High Frequency Layer and go to Image and select apply image. In the drop down select your low frequency layer and check the invert box and set the blending mode to add with a scale of 2 offset 0 and apply then change the Layer Mode to Linear Light. You now have two retouch layers you can work on and you still maintain some texture in the skin.
To finish off, select the Low Frequency Layer and duplicate and name as smooth skin. Apply a blur, surface blur works best with a starting point of Radius = 7 and Threshold = 6 apply and then create a black mask, Now painting with white over selected parts of the image will smooth out the skin.
Experiment with the settings to get the effect you are looking for. Also, when cloning and healing on the high and low frequency layers look to see what is effected which will give you a better idea on the seperation technique.
Here is a quick example of this technique
The Before Image
The After Image
Mike