Screen Magnification for Mac

Description

Zoom is a built-in, full-screen magnifier that can magnify the items on the screen up to 40 times. You can activate it using keyboard commands, a button on the screen, a trackpad gesture, or the scroll ball (or wheel) on a mouse. Thanks to the powerful Quartz rendering engine in Mac OS X, text, graphics, and even motion video can be magnified without affecting system performance.

There are three options for how the screen image moves as you type or move the mouse cursor. It can move continuously as you move the cursor; it can move only when the cursor reaches the edge of the screen; or it can move so that the cursor remains in the middle of the screen — great for those with a narrow field of vision. It’s also possible to set a minimum and maximum magnification value for instant zooming to a particular magnification and to prevent the magnification from going too high or low, leaving the system unreadable.

Where can I find out more? 
http://www.apple.com/accessibility/macosx/vision.html