Now, imagine coming up with a new way to light a portrait when everyone does it completely differently - that is what separates a genius from the rest.
Yousuf Karsh is my favourite photographer hands down. The idea of using blue sensitive film for Hemingway's photo itself deserves the highest praise - what would be a better way to emphasise subject's personality in this case.
And going back to the original topic of what is outside of the comfort zone...
That would be nude or semi-nude stuff for me - I just have no idea how to do it, or how to make an attempt in doing it, or where to draw a line between the fact of nudeness and art.
I am curious, but I am too afraid of making mistakes going that way - I don't want my peers to say, "now you went completely pervy."