There are many ways to take a screenshot in Mac OS X, but all of the well-known options give you a drop shadow for windows seen in the picture.
If you use the Command Shift 3 shortcut, it takes a screenshot of the entire screen. If you use the Command Shift 4 shortcut, it lets you select a portion of the screen. If you use Command Shift 4, followed by Spacebar, you get an option to take a screenshot of a specific window.
That last option is really useful, as it lets you select a full window without your desktop or any additional app windows behind it cluttering things up, but it still adds a… more
Sig Nordal 