Compare Images in different folders?

Just a note for any Mac users reading this thread — on the Mac, to view multiple sources at once (folders or collections or both) you want to Command-click each folder, not Ctrl-click.

And for both Mac and Windows, Shift-clicking selects a range of sources in the same list. In other words, the multiple selection modifier key shortcuts work the same as they do on the Mac or Windows desktop.

Something I just learned:

You can display the contents of multiple folders in the same grid by selecting the first folder then CTRL-click on the extra folders.

Another alternative would be to create a collection specific for the images that you want to compare.

CTRL click the folders to select them.

You can use the "All Photographs" view.

Or put the desired photos into a Quick Collection.

Or assign the photos a specific keyword, and then find all the photos with that keyword.