My current primary field of interest and study, perhaps rising at some points to the level of expertise, is early color photography.
By "early color photography" I mean before Kodachrome and, in recent years, especially before Autochrome.
There is an exasperating amount of misinformation on the subject being endlessly propagated online, especially by means of that cloning medium for fallacies, the "timeline," so easy to cut and paste. Contributing to Wikipedia seems like the most potentially effective way to expend any efforts to correct it.
More disturbing is that in the light of the contemporary sources which are increasingly available online, it is apparent that some "facts" which I have accepted as gospel for decades because of their appearance in gilt-edged reference books are simply wrong. Evidently, even the most respected authors can fall into the error of simply repeating the conventional wisdom from the previous generation of books. It is of course unrealistic to expect every detail to be followed back through the chain of references to its source for a fact check, but that serious errors can go uncorrected for so long is surprising.