This point was made long ago by J.L. Austin in (I believe) Sense and Sensibilia. Austin points out several things about "real", among them that "real" is substantive-hungry: You can't answer "Is such-and-so real?" without asking first, "Is it a real what?"

A decoy duck is not a real duck, but it is a real decoy -- whereas a rubber duck is not a real decoy; and a decoy coot might be mistaken for a decoy duck if you know little of waterfowl, but isn't a real decoy duck.

There is no sense of "real" that applies to all substantives that we would describe as real. The word makes sense only in contrast to specific ways of being unreal: being a forgery, a toy, an hallucination, a fictional character, an exaggeration, a case of mistaken identity, a doctored picture, etc. It is these negative concepts, and not the concept of "real", that actually do all the explanatory work. "Real" is both ambiguous and negative.