By non-linear I was struggling to remember stuff I've long since forgotten. Fortunately as memory fades Internet search engines improve so here's the shape I was after, courtesy of this article
on Answers.com about sensitometry:
There's also a detailed explanation in this Kodak paper
(PDF file). If I'm interpreting it correctly the shoulder area in the graph above allows a greater dynamic range to be captured than would otherwise be the case. As I understand it the sensors we are familiar with in our cameras are essentially linear in their response until (my interpretation) that sudden cut-off when the well is full, though the shape of the output is modified by a gamma correction
. Non-linear sensors have been produced but apparently suffer from problems such as fixed pattern noise (source
) so don't really feature in consumer cameras.
But essentially all the above falls into the category of too much information for our discussion as the benefits of film are very visible in the sections of the shoot-out
showing the light bulb. But maybe DSLRs shine in low light situations - sorry, bad pun.
I'm looking forward to Episode 2 of the shoot-out.