How Zoom Uses Space in a Viewport

The displayed image uses as much of the available space in the viewport without distorting the image, and unless otherwise specified, the image is centered by default in the viewport.

In Example A, the image initially uses Zoom to Fit and has unused space on both sides. In Example B, the image is the same image. However, this image displays more of the zoomed image by occupying the unused space:

Example A	Example B