How to fix screenshots from a broken scale value

From Tim:

Don’t know whether you’ve ever tried:

        defaults write NSGlobalDomain AppleDisplayScaleFactor 1.50

to set the global scaling (works pretty well except some apps actually go all fuzzy and others look fabulous)? It turns out it breaks the cmd-shift-4 to snapshot the screen and save the image to a file. The general advice if you google this stuff is to do:

        defaults write NSGlobalDomain AppleDisplayScaleFactor 1.00

to revert to normal size – which indeed it does but snapshotting is still broken. What you need to do to both revert and repair snapshotting is:

        defaults delete NSGlobalDomain AppleDisplayScaleFactor