Do you sometimes wish you had a magnifier for your computer screen? You already have one in OS X and it's actually quite good. This is how you activate the OS X Zoom feature:
Open System Preferences and click the Accessibility icon. Then click on Zoom in the left sidebar.
Activate the zoom feature by ticking the Use keyboard shortcuts to zoom checkbox. Click the More Options… button.
Set the magnification level by sliding the Magnification scale. I like to have the zoom window following my mouse cursor so I have chosen the Follow mouse cursor window position. If you would like to be able to just briefly activating zoom you should tick the Enable temporary zoom checkbox. Then whenever you want to magnify something on the screen you press Ctrl-Alt simultaneously. When you release the buttons the magnifier disappears. Quite handy.
Click the Adjust Size and Location button to set the magnifier size. I like to have mine big so I don't have to move it around all the time.
Click Done and go back to the System Settings main screen when you are done. The last thing we are going to change is the keyboard shortcuts to use for activating and zooming. Click the Keyboard icon.
Open the Keyboard Shortcuts tab and choose Accessibility in the left pane. Make sure the Zoom checkbox is ticked in the right pane. Doubleclick the keyboard shortcuts and press the keys you want to use for each shortcut. I use Ctrl-Alt-Z to toggle zoom on/off and Alt-Cmd-+ or - to zoom in and out. In all honesty I don't zoom in and out much. I mostly toggle on and off.
This feature is great when you want to read small print or work with image details.