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

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  • Subject: Re: curves and gum and Christopher James book
  • From: Michael Koch-Schulte <mkochsch@gmail.com>
  • Date: Mon, 10 Mar 2008 22:34:08 -0600
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On Mon, Mar 10, 2008 at 9:04 PM, Don Bryant <dsbryant@bellsouth.net> wrote:
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.
Can you please explain your differentiation of modes, graphic and bin, as
you have mentioned above?
There are two scales that can be used for measuring tones in the curves dialogue the scales can be toggled with the double-arrowed button on the bottom gradation. One scale goes from 0 to 100 per cent. It's commonly used to define screen blackness in the graphic arts field, 0 being white (no ink) and 100 being black. The second scale goes from 0-255. This scale evolved from the binary math used in computers. 0 is black and 255 is white. (In truth both scales are binary behind the scenes in Photoshop) The first was a paradigm so widely used for so long that it's part of the graphic lexicon. When an graphic artist asked a offset press camera operator for a 10 per cent grey screen they knew what they were talking about. Photoshop started out as a graphics editor and evolved into a photo editor.
  When someone figures out how to take a curve and programmatically graft it
onto a custom ICC profile life will becomes much simpler for digital
negative "curvers" because it'll become as simple as selecting a paper in
the print dialogue.

This May, Keith Taylor will be speaking at the f295 symposium in Pittsburgh.
The topic of his presentation will be his method gum printing which includes
his use of color management and the use of ICC profiles.

Printer profiles can be created by colour management systems made by companies like Graytag-MacBeth. But the price tag for them is also relatively high. Also I'm guessing one would still have to fiddle and adapt because these systems are geared toward paper output and not transparencies bathed in UV. Who out there needs to make giant contone transparency negatives? Besides us? ;^). I've been playing around with one application which allows me to modify an existing ICC profile. I've been able to "fatten" it so that it pumps out more ink similar to using a RIP. If you want to get serious control of the printer though then using a RIP is the ultimate. Again though cost (financial or educational) can be a serious hindrance.

Don Bryant