Clarity in GIMP (Local Contrast + Mid Tones)

I was thinking about other ways I fiddle with Luminosity Masks recently, and I thought it might be fun to talk about some other ways to use them when looking at your images.

My previous ramblings about Luminosity Masks:

Getting Around in GIMP - Luminosity Masks
Getting Around in GIMP - Luminosity Masks Revisited

The rest of my GIMP tutorials can be found here:

Getting Around in GIMP

If you remember from my previous look at Luminosity Masks, the idea is to create masks that correspond to different luminous levels in your image (roughly the lightness of tones). Once you have these masks, you can make adjustments to your image and isolate their effect to particular tonal regions easily.