As Chuck pointed out, drawing from photos was a common practice in those days. Consider that Rebour made 20-30 drawings from each visit at the show. I know he was known as a fast draughtsperson, but still, he wouldn't have done much else at the show. Also, I think there would be photos of Rebour with his easel obstructing the aisles...
I was told by a collector friend in France that they had found some photos taken by Rebour that matched his drawings. This was told as a revelation, that Rebour in some way "cheated." But as Chuck pointed out, one would expect Rebour to do it that way. The quality of Rebour's work speaks for itself, no matter how it was achieved.
To change focus a bit, does anybody know how Frank Patterson did his drawings? I read that he was not able to ride or get out much due to health reasons, so I doubt he was drew in the countryside. And what about his furniture drawings? Does anybody know?
Jan Heine, Seattle