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: Ender100@aol.com
  • Date: Mon, 10 Mar 2008 23:07:11 -0400 (EDT)
  • Comments: "alt-photo-process mailing list"
  • Delivered-to: alt-photo-process-l-archive@www.usask.ca
  • List-id: alt-photo-process mailing list <alt-photo-process-l@sask.usask.ca>
  • Reply-to: alt-photo-process-l@usask.ca

An easy way to compare a curve applied to a positive vs a curve applied to a negative is to do the following:

1.  Take a 21 step digital step tablet

2.  Apply your curve to the step tablet

3.  Flatten the layers

4.  Use Image>Adjustments>Invert

5.  Read the values of the steps with the eyedropper tool

6.  Create a curve with points that have the output values set to the values you read for each step

Hope this helps!

Mark Nelson
Precision Digital Negatives
PDNPrint : Precision Digital Negatives
Mark I. Nelson Photography

In a message dated 3/10/08 8:51:30 PM, cryberg@comcast.net writes:

Folks:  Several of you have responed to Henry's question with suggestions of
what he might do--but that was not his question.  He wants to know--and I do
too--how one person's curve for a positive can look much like another's
curve for a negative.  One answer seems to respond to his question, but I
don't understand it--here it is:

You have to REALLY pay attention to the curve mode being used to display the
curve. A curve calculated for graphic mode (applied to a positive) will, on
the surface, look exactly the same as a curve applied to a negative -- BUT
since PDN users generally work in binary mode it is this change of mode
which functions to invert the curve.

What is a curve calculated for graphic mode?  Why will it look exactly the
same a a curve applied to a negative.  What is binary mode as opposed to
graphic mode?

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