The lightbox has a "use this file" link which pops up a dialog box with some text you can cut-n-paste for on-wiki or random HTML markup containing the image... but there's no visible way to get at a medium or high-resolution copy of the image for download.
I find this is a frequent use for me, as I like to take Commons Photos of the Days as desktop or phone wallpapers, or take images to reuse in presentations etc.
Such a tool should probably offer several predetermined sizes and an "original file" download link, similar to what appears on the file description page, but .... user-friendly. :)
Version: unspecified
Severity: enhancement
URL: https://test.wikipedia.org/wiki/Lightbox_demo