Re: Back-exposing on plastic (was: Re: Gum transfer

Mark,

is it because you want us to buy your book and you don't want to reveal important notion or is it something else but anyway your last paragraph below is totally incomhensible.

Regards
Yves

  ----- Original Message -----
  From: Ender100@aol.com
  To: alt-photo-process-l@usask.ca
  Sent: Tuesday, May 02, 2006 3:50 PM
  Subject: Re: Back-exposing on plastic (was: Re: Gum transfer

  Katherine,

  I am not sure I understand your statement below. I understand that gum is a short scale process (requires a negative of a shorter exposure scale, like in the range of log .9 maybe to log 1.2, give or take a log or a twig—or from your example below, between log 1.5 and log 1.8?

  I also understand that no curve on a digital negative is going to change the exposure scale of a given mix, and certainly the curve is not going to INCREASE the printed gum DMax.

  What I am not sure I understand is if you are saying that for a given mix of gum printed with one coat, changing the shape of the curve will NOT allow you to get whatever tones you want between the DMax of this given mix (one printing) and paper white? And further that you can only obtain some of the tones ? Which ones?

  Let's assume that a digital negative can have a maximum of 256 possible tones of density. (If that is ok with you) and that a radical curve is going will reduce the number of tones from 256, so let's consider a not so radical curve. Let's also assume that the negative matches the exposure scale of the gum mix before the curve is added.

  Best Wishes,
  Mark "Gum Impaired" Nelson
  Precision Digital Negatives--The Book
  PDNPrint Forum at Yahoo Groups
  www.MarkINelsonPhoto.com

  In a message dated 5/2/06 1:52:38 PM, kthayer@pacifier.com writes:

    Yves, I hope seeing Chris's print comparison will help you finally
    grasp what I've been saying. No, you cannot, once you've got the
    right emulsion, "basically obtain any tone you want between the DMax
    and the Dmin of the print" by adding a curve. With gum, you can
    obtain some of the tones running between Dmax and Dmin, but not all
    of them, not by a long shot, (this is what we mean when we say gum is
    a "short scale" emulsion, or that no matter what you do, you can't
    get more than 10-12 steps on a 21-step for gum in one coat by the
    usual method-- that's assuming a normal pigment load; you can get
    more, but paler, steps with a lighter pigment load, or fewer, but
    darker, steps with a heavier pigment load).
Received on 05/02/06-04:16:56 PM Z