We generally think of masks as selection as either activating an area or excluding it from any editing. But it is possible to make a selection that only affects an area partially. For example, if an area is partially selected, painting with black will result in a gray stroke that is lighted or darker, depending on how much it is selected. The effect is similar to when a selection edge is feathered, and the effect is faded out toward the edges.
I refer to them as translucent selections in the context of Quickmasks because these partial selections are painted on using a gray color rather than straight black. The darker the gray, the more the area will show the effect, while masks painted with a lighter gray let the effect show through more slightly. Translucent masks allow areas and layers to fade into one another, creating smooth transition effects. The following step be step shows how to set up these transition areas easily using Quickmask.
Once the above translucent selection is created, its a simple matter to delete it to the background color or to reveal a lower layer (Figure 18.4). You could also fill the selection with a color, pattern, or even a pasted image. In this case, I simply deleted the selection to white.
Remember that you can start a Quickmask from any standard selection approach. Try creating a color based selection and converting that to a Quickmask for further selection modification.