Simple frequency seperation in GIMP any better ways?

[teaking]

I have been reading a lot of stuff about frequency seperation, especialy for skin retouching and have saw many ways in which to do it I have been playing around in GIMP and using a DIY high pass filter which I found the tutorial for here I have found you can kind of replicate a high/low frequency technique. I just wondered if anyone had tried anything like this?

1. So if you start off with your image, duplicate it and then apply a gaussian blur for example 5px (you can use what ever you like depends on the details you want to control later.
   
2. Duplicate your background layer again and duplicate your blurred image.
   
3. Move one copy of the blurred image to the top and move one copy of the background image below the blurred image
   
4. Change the blend mode to grain extract, you now have the highpass looking thing merge the top layer down you now have a high pass layer we will call this high frequency
   
5. The remaining blurred image should be below the detail layer and we will call this low frequency
   
6. Move your original back ground image to the bottom if its not already.
   
7. Change the high frequency layers blend mode to grain merge and you should have the original image. (you still have a copy of your oringal background image to compare with)

So whats the point of the messing about... well:

• if you take the high frequency layer open curves and put a marker at 128/128 (this protects mid tones) and then apply a sharp "S" curve you should notice quite a nice sharpening effect
  
• Also if you take the low frequency layer select some skin and then apply a gaussian blur at about 15px you should notice the skin tones seem to even out.... thats why I originaly started at 5px as I saw a great post about skin tone evening.
  
• You can even go into the detail layer and use the clone tool to remove blemishes.

Just though it was interesting and maybe a little more advanced for other GIMPers out there something someone could play with maybe find a better way of doing it... and just to share.

[wulf]

A better way of doing this would be to write a script that performs the donkey work for you - creating and moving various layers and applying filters. You could then come back to the step of sharpening the curve on the hi-fi layer to add sharpening, etc, where an eye for detail is called for.

It adds more visible feedback to the method outlined in the DIY High-pass thread although also takes some extra steps. However, what interests me is putting the hi-fi layer back into grain extract mode - that gives a wacky result which reminds me of the fractilicious plugin. I might experiment with that a bit more, with different levels of blurring.

Wulf

[teaking]

thanks for the feedback Wulf I think you are spot on about the scripting taking the donkey work out and getting the process to a one or two button press would improve on a lot of thing

I better get reading scripting.... Oh I ever though of turning the layer to back to grain extract again it certainly does give a wacky result I think I kinda like it from an artistic point would be interesting to hear where it leads you if anywhere.