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QTR for Gumprinting

QTR for Gumprinting

2018-03-05 by sebastien.brias@...

Hi everyone,

i would like to use QTR for colour Gumprint.

I had adjust a curve for the cyanotype (first layer)

but as this process involve several layers with different settings (colour, exposure, etc)

Do i have to set up a different curve to each of the three colour CYM?

(because they don't "behave" the same)

AND a different curve to each stage (incrasing/decreasing exposure) ?


Or there is a way to create a single curve who can fit to the whole process?



Sébastien

Re: QTR for Gumprinting

2018-03-05 by donsbryant@...

The short answer is yes you will need to apply a curve file for each color printed. The file is derived by printing a digital step tablet separately with the pigment coated alone without the interaction of other pigments.

Re: [QuadtoneRIP] QTR for Gumprinting

2018-03-05 by Simone Simoncini

Hi. It depends on what you are looking for.
If you aim for a fair amount of control over the process, you should standardize as much as possible and yes, make a curve for each layer.

I am doing the same thing these days.

Once you have done the curves, you should print an rgb target and make a profile by using a spectrophotometer.

Then, before you make ypur separations, ypu should convert your image in the icc profile ypu created.



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Il 05 mar 2018 16:30, "sebastien.brias@... [QuadtoneRIP]" <QuadtoneRIP@yahoogroups.com> ha scritto:

Hi everyone,

i would like to use QTR for colour Gumprint.

I had adjust a curve for the cyanotype (first layer)

but as this process involve several layers with different settings (colour, exposure, etc)

Do i have to set up a different curve to each of the three colour CYM?

(because they don't "behave" the same)

AND a different curve to each stage (incrasing/decreasing exposure) ?


Or there is a way to create a single curve who can fit to the whole process?



Sébastien

Re: [QuadtoneRIP] QTR for Gumprinting

2018-03-05 by Sébastien Brias

Thank you Simone,

I haven't a spectrophotometer, just a flatbed scanner

if i separate each channel in PS and apply the dedicated curve to each colour,

will it do the job?

Re: [QuadtoneRIP] QTR for Gumprinting

2018-03-05 by Paul Roark

Regarding linearization with a flatbed, see the StepWedge tool at http://www.quadtonerip.com/html/QTRdownload.html .

Paul
www.PaulRoark.com
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On Mon, Mar 5, 2018 at 8:03 AM, Sébastien Brias sebastien.brias@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Thank you Simone,

I haven't a spectrophotometer, just a flatbed scanner

if i separate each channel in PS and apply the dedicated curve to each colour,

will it do the job?


Re: [QuadtoneRIP] QTR for Gumprinting

2018-03-05 by Sébastien Brias

Cool, i have it.

Thank you Paul

2018-03-05 18:11 GMT+01:00 Paul Roark roark.paul@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com>:

Regarding linearization with a flatbed, see the StepWedge tool at http://www.quadtonerip.com/html/QTRdownload.html .

Paul
www.PaulRoark.com

On Mon, Mar 5, 2018 at 8:03 AM, Sébastien Brias sebastien.brias@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Thank you Simone,

I haven't a spectrophotometer, just a flatbed scanner

if i separate each channel in PS and apply the dedicated curve to each colour,

will it do the job?



Re: QTR for Gumprinting

2018-03-05 by donsbryant@...

No. Each pigment layer has it's own ACV curve. You need to linearize each layer. A composite target will probably have a color bias, possibility different in the shadows, midtones, and highlights. Get the print density correct before color correcting. Instead of an ICC profile you can create a color correction layer. There are no simple answers but you need to work methodically. 

We haven't"t even discussed pigments, BTW.

Re: [QuadtoneRIP] QTR for Gumprinting

2018-03-05 by Simone Simoncini

I think the most practical approach is to try and balance the scale.for each colour to achieve a fairly smooth rendition of the gradient. After that, in gum printing in my opinion is not so relevant to seek precision and you can balance the colour rendition with practice.

Tha approach I told you about is what I am trying to do because having a hp z3200 i can experiment with a specific process developed by hp itself, which is only an adaptation of a colour managed workflow.

A flatbed scanner will do for example, if you use one of the methods available (i am fairly confident with the Charthrob script just to mention one). They all do the same thing. A densitometer or a spectrophotometer will be more precise, but a scanner will do fine to balance the "scale" of each individual color.

Will not do any good to create a colour managed workflow, that is... putting all the colors together and create your own tecnique color space, which is an entirely different matter.

If you haven't yet, I recommend you to read Christina Anderson's books on gum printing, they tell you everything you need to know.. even more. In her books you will appreciate how gum is a tremendously flexible tool to develop your own way of express things. I began a few months ago, it is fascinating!

Bye and have fun!
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Il 05 mar 2018 17:05, "Sébastien Brias sebastien.brias@gmail.com [QuadtoneRIP]" <QuadtoneRIP@yahoogroups.com> ha scritto:

Thank you Simone,

I haven't a spectrophotometer, just a flatbed scanner

if i separate each channel in PS and apply the dedicated curve to each colour,

will it do the job?


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