With the help of zoom, an operator can scale the image and review distant objects.
The 
button enable/disables zoom mode.
You can scroll the mousewheel to change the zoom level or use single mouse clicks -left (to zoom in) or right (to zoom out). Left click to move the zoomed area on the image.
If Picture-in-picture mode at zoom is selected in the view options, you'll see the camera image in the right upper corner and the zoomed zone will be highlighted with a red rectangle. You can move the zoomed area on the image by moving the red rectangle.
Tip
Zoom can also be activated by pressing CTRL and deactivated by releasing it.
