When you make a selection in Photoshop CS, you can add to it or subtract from it by using the Add to selection and Subtract from selection buttons on the options bar.

 

 

 

For this example, we will make a simple rectangular marquee selection by choosing the rectangular marquee tool, and dragging a rectangular shape over the image.

 

 

Now, the next step is to click the Add to selection button on the options bar, and drag another rectangular selection over the first.

 

As a result, the two selections are combined to make one large selection.

 

 

When you use a tool to make a selection, you don’t have to use the same selection tool to add to it. For example, the elliptical marquee tool could have been used here just as easily in combination with the rectangular marquee.

 

To subtract from a selection, choose a selection tool and then click the Subtract from selection button on the options bar. For this example, the elliptical marquee tool is used to subtract an elliptical selection from the composite selection shown above.

 

When you have set the Subtract from selection option, you can just create your selection in the normal way (mouse dragging in this case).

 

 As you can see, the elliptical selection is visible inside the rectangular selection, indicating that the elliptical area will be subtracted from the selection. Here is the resulting final selection (darkened for illustrative purposes).

 

Selections made with various tools can be added and subtracted to create some interesting patterns and effects. Don’t be afraid to experiment with the selection tools and their options.

 

Note: When you have finished building your selection, you may want to click the new selection tool if you wish to move it around or perform other manipulations.