This version introduces Quick Preview. It is similar to QuickLook in Finder. Press spacebar in Contact Sheet mode and the Quick Preview window will pop open. Press spacebar again to close the window quickly.
You can zoom and pan around the image in this window with the Trackpad. Move this window to a secondary display and you can have a dual display setup. You can even use your iPad as secondary display with app such as Duet Display.
Moving around with the arrow keys in Contact Sheet will update the image in the Quick Preview window.
There is new arrow keys mapping. HJKL maps to ←↓↑→. So you can move around the Contact Sheet and press the spacebar just using one hand. Previously, the H shortcut key was mapped to "Zoom to fit window height". It is now mapped to the E key.
There is an internal display engine improvement. When an image is zoomed in, the panning performance is vastly improved for macOSes prior to Mojave.
Hope you guys enjoy this update. Merry Christmas and Happy New Year!