In 10.5, the region capture screenshot tool—that’s Shift-Command-4, which turns your cursor into a draggable crosshair—has learned quite a few new tricks. Since the days of 10.2, if you added the Control key into the mix, the capture would go to your clipboard, instead of to a file. (This is a great way to grab a quick screenshot for an iChat session, by the way. Just Shift-Control-Command-4, drag around the area to capture, release the drag, then switch back to iChat and hit Command-V to paste.)
But with 10.5, Apple has found uses for the Shift, Space, and Option keys as well. This gets a bit complicated, but I’ll try to explain it clearly, then demonstrate with a short movie. If you start a region capture, either with or without the Control key, you can then change how the region selection area changes by using the following keys—note that you can release the original keys once the crosshairs appears, as long as you’ve started dragging your mouse, and you keep the mouse button down.
Space Bar: Press and hold the Space Bar, and the size of the current region is then locked and can be dragged around the screen. As long as you hold the Space Bar down, the region’s size is locked and it can be dragged about.
Shift: Press and hold the Shift key, and one side of the region will be locked, based on which way you then move the mouse. For instance, if you press and hold Shift, and then move your mouse down, you’ll only be able to resize the region vertically; the horizontal size will be fixed. Move the mouse left or right, and you can resize the region horizontally while holding the vertical size fixed.
Option: Press and hold Option while dragging your region, and you’ll change the way the region grows as you drag. By default, your region is anchored at the upper left corner; when you press Option, the anchor point is moved to the center of the current region, and it expands in all directions from that point.
To make things even a bit more confusing, you can combine some of these keystrokes. Shift and the Space Bar together will allow a fixed-size region to be dragged in either a vertical or horizontal direction, depending on which direction you first move the mouse after pressing the keys. If you combine Shift and Option, then you can grow your region from the center, restricting either the vertical or horizontal size. As I said, it’s a bit confusing, so here’s a movie of the options in action.
As you can see, with these new modifier keys, there’s a lot more flexibility in capturing regions—either to a file, or to the clipboard when you add in the Control key.