Using the magnifier tool

In preview mode, select images/download/attachments/74458296/image2017-10-27_11_22_10.png to use the magnifying tool. The cursor does not change, but after selecting the icon, select and hold the cursor over the item you are previewing. A section of the item is magnified, similarly to how a jeweler's loupe works. You can move the magnifier around to view all different parts of the item.

This option is available only in the desktop view.