Opacity Masks in Illustrator CS

Opacity Masks in Illustrator CS: This article helped me understand how to use transparency in Illustrator. One of the things that I did not find in my reading of the article (more like detailed skimming) was how to exit opacity mask mode. The only way that I could figure out was to to back to the Transparency window and click on the left of the two preview panes. Maybe this would be obvious to a more proficient Illustrator or Adobe products user as clicking on the right hand preview put you in opacity mask editing mode.