In recent tips, we've discussed using the Preserve Transparency option to confine painting or editing to the existing object on a layer. For example, if there were a red ball on a layer with Preserve Transparency turned on, you could choose a paint brush, sloppily paint all around the layer, and still change only the color of the red ball.

You cannot turn Preserve Transparency on in type layers. The only way to affect the transparent area of a type layer is to convert the type layer into a normal layer. To do so, choose Layer, Type, Render Layer. At this point, you can turn Preserve Transparency on and off as you normally would.