Program a Function Key, OSX Mountain Lion

Question

Hello,
I have just learned that if I hold down a whole bunch of buttons I will be able to capture the image of an active dialogue box in an application and have Mac save it automatically on my desktop. The combinations are: Command + Shift + 4 + Spacebar + Ctrl.
That is a lot of buttons to be pressing simultaneously and also difficult to remember.
Is there a way to redefine a function key on the keyboard to execute the combination of the commands?
My goal is to capture dialogue boxes of some applications because I am writing articles about features and usability. Do you have any other suggestion as to how to do this?
Thanks in advance.
Farzad

Answer 1

You don't have to hold all of those simultaneously.
Cmd-Shift-4 gives you the selection icon, where you can drag out what you want.
If you then hit the spacebar (not holding anything else down), the cursor will change to a camera and you can select entire windows.
Either way, if you hold down control while you click, it will go to the clipboard instead of saving to a file. The shortcut is actually listed as cmd-ctrl-shift-4, but since there is a second click involved, you can press the control key while you click.
Cmd-shift-3 does the whole screen. If you want the whole screen to go to the clipboard, you do have to hold down cmd-ctrl-shift-3.
You can change keyboard shortcuts in the Keyboard System Preferences, Keyboard Shortcuts tab, Screen Shots item.