color management for tricolor gum

nze · Feb 20, 2009

Hi all

I am still working on tri color gum. I am closed to good result but just find that using the digineg setting of Dan burkholder ( which work greatly for creating my platinum neg) . Here I have a problem there is some yellow in the magenta and some magenta in the cyan. when I make a reading of a 100% point in one of this color there aren't at 100% and there is some % in the color.

I find that Prophoto setting give me good reading in Magenta and yellow but not in cyan

Does any one already solve this or have any helpful idea.

Best

Katharine Thayer · Feb 21, 2009

Hi Chris,
I wonder if you could expand a little on your question. I'm not sure what you mean by "yellow in the magenta" for example. I'd be glad to help, but I'm not quite understanding, sorry.

P.S. There's an old thread on color management for tricolor gum printing in the "calibration" forum here; it veers off to gum topics not related to color management, but you might take a look at it just on the chance that it touches on your question.
Katharine

donbga · Feb 21, 2009

nze said:
Hi all

I am still working on tri color gum. I am closed to good result but just find that using the digineg setting of Dan burkholder ( which work greatly for creating my platinum neg) . Here I have a problem there is some yellow in the magenta and some magenta in the cyan. when I make a reading of a 100% point in one of this color there aren't at 100% and there is some % in the color.

I find that Prophoto setting give me good reading in Magenta and yellow but not in cyan

Does any one already solve this or have any helpful idea.

Best

Christian,

I'm not clear about what you are asking or stating.

Do you mean that your digital step tablet when printed isn't neutral in color? With magenta and yellow crossing over with the cyan and magenta?
Please post an image if possible.

Don

nze · Feb 22, 2009

I was sure I wasn't clear.
yes there is some cross over from the yellow to the cyan and magenta. But as I do the separation in PS it already show some cross over : foe example the Cyan square is totally black in Cyan but also light gray in yellow.

I refining the process before I'll do a ICC profile for the pigment I use. I also have another alternative using personal parameter in the PS color setting

nze · Feb 22, 2009

Ok I read the thread on gum calibration. in fact I can produce neutral grayscale. but as my color space in PS is not similar to colorspace of my tricolorgum . So there are some change in the color even if the grayscale is neutral.
At this point I think that theonly solution is to work in a color space which is similar to my gum space ( same gamut). I already have some idea on how to do that , but as color is a new thing to me, I prefer to ask.

The funniest thing for me is that I use to make some tricolor gum 20 years ago and I get good result just making separation with the old filter and some panchrofilm.

Katharine Thayer · Feb 22, 2009

Yes, it seems to me that as people make tricolor gum more and more complicated, the more difficult it gets. I also had no trouble getting good results with just inverted channels printed on a laser printer, 20 years ago. I wonder if we're not making things more complicated than they need to be.

But I do understand now what you mean and where you're going, with the added info about how you're looking at a square that should be 100% one color, but isn't. I guess I can't offer any advice because I've never got that deeply into it, but I'll be very interested to hear the results of your explorations. This is what people have been saying for years that we need ultimately, but I've never been interested enough in perfect color management for gum, to do the explorations myself. Good luck,
Katharine

nze · Feb 22, 2009

katharine

I did the same these last weeks ( talking of laser printer) and I get excellent result without any curves. I also try image setter with good result. But I just have a inkjet printer at home and try to make good digineg with it.
I 'll keep you inform of my exploration

donbga · Feb 23, 2009

nze said:
I was sure I wasn't clear.
yes there is some cross over from the yellow to the cyan and magenta. But as I do the separation in PS it already show some cross over : foe example the Cyan square is totally black in Cyan but also light gray in yellow.

I refining the process before I'll do a ICC profile for the pigment I use. I also have another alternative using personal parameter in the PS color setting

How are you creating your separations?

CMY or CMYK?

Don

Katharine Thayer · Feb 24, 2009

Don Bryant said:
How are you creating your separations?

CMY or CMYK?

Don

Good question. I was assuming RGB>CMY, since Chris referred to "tricolor gum." If it's CMYK, that's a whole 'nother ball of wax, and would explain why the color values are altered. So I'll be interested in the answer.
kt

nze · Feb 24, 2009

I use to separate my RGB file and invert each color so RGBneg become > CMY.
I read all your text on the subject Katherine , so I prefer transparent color and RGB

Katharine Thayer · Feb 24, 2009

Thanks, that's what I was assuming. Well, then I'm at a loss as to why you're getting color overlaps in what should be pure color separations. I'll drop back to my previous post and repeat: good luck and I'll look forward to hearing what you find out.
Katharine

nze · Feb 27, 2009

Hi all

Still working with Ps , but this morning I give a try to Gimp and it separte the RVB just as I want without any color cross over. I will use the same colorparameter in PS and hope it works too.

donbga · Feb 27, 2009

nze said:
Hi all

Still working with Ps , but this morning I give a try to Gimp and it separte the RVB just as I want without any color cross over. I will use the same colorparameter in PS and hope it works too.

Christian,

As I am recovering from serious foot surgery two days ago my energy to research your problem is quite limited now. My recovery won't be for about 8 weeks. When I'm back in action I'll try to look into this.

As Katherine wrote, I'm at an immediate loss for an answer.

Cheers,

Don Bryant

nze · Feb 27, 2009

Don and Katherine

I am working on ICC profile for my gum and try to find an easier way which will be to make a new RGB profile by reading my Red grenn and blue value . I t is possible on pohotoshop to have a personnal RVB , just have to put some info in it. If it works well PS should separate the file and adapt it to my pigment and paper color.

color management for tricolor gum

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