Activate an Orthographic viewport. > Viewport navigation controls > Region Zoom
Activate a Perspective viewport. > Viewport navigation controls > Region Zoom (from Field of View flyout)
Keyboard > CTRL+W
Zoom Region magnifies a rectangular area you drag within a viewport. This control is available only when the active viewport is an Orthographic, Perspective or User- Axonometric View. It is not available for Camera viewports.
Zoom Region stays active until you right-click or select another command.
Procedures
To zoom a region:
Activate an Orthographic or Perspective viewport.
Click Zoom Region or press CTRL+W.
When you zoom a region in a perspective viewport, select Zoom Region from the Field of View flyout.
Drag a rectangular region in any viewport displaying a non-camera view.
When you release, the region is magnified to fill the viewport.
Note: When using the Region Zoom in Perspective view, the zoom rectangle is at a fixed distance from the camera. For this reason, if you draw the rectangle large enough, you can zoom out from the scene.