Use the Magnify Rectangle tool to magnify around a specific area of an image, rather than from the center, as with the Zoom tool. Unlike Magnify Glass, Magnify Rectangle magnifies the image in the same window.
To magnify a region of the image
From the Image area context or top toolbar, click Magnify Rectangle.
or
If using the context toolbar text menu (Ctrl + right-click), select Magnify/Pan > Magnify Rectangle.
Magnify Rectangle may be the default tool, in which case you do not have to activate it. When active, the pointer has a rectangle shape attached to it.
To enlarge or reduce the rectangle before you place it, move the mouse scroll wheel.
Place the pointer over the area to magnify, then click.
To magnify the image more, repeat steps 2 and 3.
To pan around, drag the pointer in the direction to move the image or use the Pan tool.