1. From the Viewer, select the image(s) you want to magnify.
2. In the Image tab of the toolbar, click Magnify 
.
Press Alt and move the cursor to adjust the default size of the magnifying glass area.
Press Ctrl and move the cursor to increase the zoom level while leaving the area of the magnifying the area of the magnifying glass the same.
Press Shift to change the windowing within the area of the magnifying glass.