You can view photos as thumbnails, in a list, or one at a time. Choose View ▶ as Thumbnails (⌘1), as List (⌘2), or as Slideshow (⌘3), or click one of the view toolbar buttons:
Double-click a photo in thumbnail or list view to switch to slideshow view. You can customize what happens when you double-click a photo in the Photos preferences.
You can also hit the return key to display the selected photo, and then hit return again to go back to the list.
To go into full screen mode, choose View ▶ Full Screen. Hit ⌘` to toggle full screen mode. (You can also hit Escape to get out.) In full screen mode, you can switch views using the keyboard. Or if you have dual displays, you can show photos on the main screen and thumbnails on the second screen.
You can refresh the list by choosing View ▶ Refresh. If you are in slideshow mode, the current photo will be reloaded too.
The thumbnail view shows the same icons that you see in the Finder. In the Photos preferences, you can choose whether thumbnails should be created automatically, and whether to create smooth (anti-aliased) thumbnails. To create thumbnails manually, choose Photos ▶ Create Thumbnail. To update existing thumbnails, hold down the Option key.
You can choose whether to show the rating for each thumbnail by selecting View ▶ Thumbnails ▶ Rating.
You can choose which columns are displayed in list view by selecting them in the View ▶ Columns submenu. (As a shortcut, control-click the columns headers.) For example, you can choose to show Comments in the list view.
You can choose how the displayed photos are sorted using the View ▶ Sort By menu, or clicking a column header. Click the column header again to reverse the sort order.
By default, small photos are expanded to fill the available space. You can turn this off by unchecking "Enlarge Small Images" in the View menu (⌘^) or the Photo preferences. You can also choose whether images are scaled smoothly (anti-aliased) when enlarging or reducing.
To get more room to display pictures, you can choose View ▶ Hide Toolbar (⌘8), Hide Status Bar (⌘9), and Hide Browser (⌘0).
To make a photo even larger, choose Photos ▶ Open in New Window (⎇⌘O).
If the selected photo has been edited in another program, choose View ▶ Refresh (⌘R) to refresh it.