You can change the zoom in the viewer using one of the following commands:
- Zoom In (the Num Plus key): zoom in to the next preset percentage,
- Zoom Out (the Num Minus key): zoom out to the previous preset percentage,
- Zoom To (the M key or the Num Asterisk key): zoom to specified percentage.
You can also use two automatic zoom modes: Fit in Window (the F5 key) and Fit Width (the F6 key). The first calculates the zoom percentage to show the whole image in the viewer window. The second to show the whole width of the image in the viewer window (it avoids horizontal scrolling, but vertical scrolling can be still needed). You can set one of these modes as default (then it is used every time you open the viewer), see Appearance tab in Configuration.
You may also often want to see the image in 100% zoom (one pixel of the image is one pixel in the viewer window). You can use the Actual Size command (the F7 key) for this zoom.
You can find all described commands in viewer menu View.
The Zoom mode in Using Mouse in Viewer.