U of S | Mailing List Archive | alt-photo-process-l | Re: curves and gum and Christopher James book

Re: curves and gum and Christopher James book

  • To: alt-photo-process-l@usask.ca
  • Subject: Re: curves and gum and Christopher James book
  • From: Henry Rattle <henry.rattle@ntlworld.com>
  • Date: Mon, 10 Mar 2008 12:53:18 +0000
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  • Thread-topic: curves and gum and Christopher James book
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Thanks, everyone, for the reviews of the new book. I'll be ordering one when
it hits the UK on April 1st.

Meanwhile, something puzzles me.

Someone mentioned David Hatton's gum curve being in the book, sourced from
the Alternativephotography website. Out of curiosity I looked it up there,
and it looks pretty similar to my own gum curves (though along with
Christina I find that different colours give different curves, especially

However one thing puzzles me - there's a note alongside the curve which says
"Note from David: The curve is applied before inversion to a negative and
the image should be RGB."

Now my practice is to apply my curves to the negatives, after splitting the
RGB channels and inverting, and before colorisation - following Mark
Nelson's PDN. 

But shouldn't the curve you apply to a positive before inversion be the
inverse of a curve you apply to a negative after inversion?

Or do I understand this even less than I thought I did? David? Anyone?