GIMP 2.2.6 - Brightening Images
I discovered this by accident. Hopefully it will be useful to you as well.
Subject: Brightening Images
Program: GIMP 2.2.6
Results:
or 
1) The cropped & resized image I'm using:
2) Filters>Enhance>Unsharp Mask.... I'm using the default settings.
3) Duplicate the layer. Change the new layer's mode to "Soft Light." Fiddle with the opacity until it looks right to you.
OR
Before doing #3, you can change the image to greyscale (Image>Mode>Greyscale) and then continue.
Subject: Brightening Images
Program: GIMP 2.2.6
Results:
1) The cropped & resized image I'm using:
2) Filters>Enhance>Unsharp Mask.... I'm using the default settings.
3) Duplicate the layer. Change the new layer's mode to "Soft Light." Fiddle with the opacity until it looks right to you.
OR
Before doing #3, you can change the image to greyscale (Image>Mode>Greyscale) and then continue.