The Duden which is for German language as important as the Oxford Dictionary of English language describes also the following structure.
Dieses Bild ist am
= This picutre is the least beautiful.
This type of phrase sounds weird and the author would advise not to use structures of this type. Nevertheless, in some cases it can be used and sounds perfectly right. As you can see, these are cases when the superlative of the adverb of quantity wenig is used without any other adverb or adjectives.