An Overview of GIMP 2.8 - Beginning Photo Retouching and Restoration Using GIMP - page 19

Layer Blending Modes
Layers have a variety of blending modes, which interact with the underlying layer in specific ways. Blending
modes can be very useful when restoring photos. For example, an underexposed photo, such as the one in
Figure 1-18 , can be quickly enhanced by simply duplicating the background layer and changing the blending
mode to Screen . The result is a brighter picture.
Figure 1-18. An overlay layer blend mode brightens up this image
It's often possible to correct images with serious tonal problems with a combination of blending modes.
It will require some experimentation but can often workvery well.
Plug-ins to Enhance GIMP
There are a number of plug-ins for GIMP that expand its capabilities. Some plug-ins are useful, some not so
much, at least for photo restoration work. You can peruse the available plug-ins at the GIMP Plugin Registry
at http://registry.gimp.org/ —there are plenty to see.