I was pleasantly surprised that Mortensen is that popular in PF
i dived into my collection of material I assembled for the purpose of an essay i did and a presentation to my club...
it is not only his Grotesque & Erotic portraiture that is of worthy note, it is also his darkroom techniques (of reversal, of colorizing etc etc...)
here are some technicals articles on it
and more...
and here are an insight to his life
enjoy the read...