An Overview of GIMP 2.8 - Beginning Photo Retouching and Restoration Using GIMP - page 17

Layers are one of the most important aspects of photo editing. Sometimes it will be necessary to make
revisions to your work, and having a layered version will make this much easier. If I wanted to redo the sun's
rays, I could hide the original layer (titled “Rays”), by clicking the eye-shaped icon, and redraw them on a
new layer (Figure 1-15 ).
You should never edit directly on the background layer! Make a copy of the original image layer to edit. In
the following example (Figure 1-16 ), I duplicated the original layer and named it Edit Layer (you can name
it however it best suits you), then desaturated it, to remove the color. The original background layer is still
intact. By adding a layer mask, I was able to paint some of the color back in for a selective colorized effect.
Layer masks allow you to add or remove data on a layer in a nondestructive way.
Figure 1-16. The work is done on a copy of the background layer
You might end up having 10, 15, or more layers in your restoration projects, depending on the degree
of work involved. It's a good practice to name the layers as you create them. If you have a project with many
layers, it will make it much easier to find a particular layer, should you need to edit it.