To return quickly to default magnification, select "Zoom To Fit tool" from the ribbon toolbar’s Active Window Tab, use the Zoom To Fit tool from the toolbar or use the zoom default keyboard short-cut (F). Zoom to fit makes sure the whole image is visible at once in the current window no matter what the window size. The Zoom to Fit All tool performs this action on all open photos.
Once the photograph is zoomed-in only part of a photograph will be visible. To change the part of the photograph that is visible when it is magnified you may use the scroll bars or one of the "panning" tools.
This tool is not accessible when the 3D Viewer is active. If in this mode and a 3D Viewer becomes active, the mode will switch to a valid mode for 3D, such as Zoom In.