G7 ink formulations

[Green Printer]

Is it possible to increase G7 color gamet with a low dot gain ink?

 

[rich apollo]

I'm guessing that you're wanting to run higher densities (thicker ink film) to achieve more saturated colors. If your ink and paper combination can achieve greater saturation, then you don't really even need to use a "low dot gain ink". You could alter the gain characteristics with plate curves. More ink does not necessarily mean more color, though. More ink will darken the solid color, and usually begins altering the hue. In extreme cases it actually reduces saturation.

You'll probably want to look for an ink set with a high pigment load. You'll need to make sure that you set up your print conditions to achieve, and maintain, gray balance.

There is a theoretical reference print condition called CGATS-21 CRPC7 that is kind of an extended gamut version of GRACoL_2013. This is a synthetic data set - it is not measured press performance.

 

[gordo]

This link explains how to do it: http://the-print-guide.blogspot.ca/2...myk-gamut.html

You don't need to go to high pigment load inks.

 

[Green Printer]

If I have a very low dot gain, run a regular pigment load and do not push the ink running at standard densities would I see and increase in the G7 color gamut.

 

[Green Printer]

Second part If the plates can be made to run closer to linear ( not linear but closer to linear) by using a low gain ink would't that open up the G7 gamut? I am thinking that less tonal compression because of dot gain compensation would effectively increase the number of colors within the boundaries of the color space.

 

[gordo]

If I have a very low dot gain, run a regular pigment load and do not push the ink running at standard densities would I see and increase in the G7 color gamut.
Second part If the plates can be made to run closer to linear ( not linear but closer to linear) by using a low gain ink would't that open up the G7 gamut? I am thinking that less tonal compression because of dot gain compensation would effectively increase the number of colors within the boundaries of the color space.

Dot gain is tone reproduction metric. It has nothing to do with color gamut - so linearity of the plate is not relevant as far as gamut is concerned. Neither, practically speaking, does "tonal compression" have anything to do with gamut.

Gamut is affected by the substrate (brightness, whiteness and absorbency) being used, by the light filtering properties of the inks (and number of ink hues being used), and by the halftone screening (more properly by the size of the halftone dots being used to simulate tones).

If you increase SIDs and then use a cut back curve to normalize tone reproduction, then (up to a certain point) you increase color saturation (chroma) which is an increase in gamut.
If you decrease the size of the halftone dots that are used to simulate tones then there will be more ink dots per area and hence more opportunities for light to be filtered by the ink and less light reflecting off the non-inked area of the substrate (that unfiltered light effectively reduces gamut). That's why FM screening does not increase gamut - it just reduces it less that a coarse AM screen).

 

[Correct Color]

Second part If the plates can be made to run closer to linear ( not linear but closer to linear) by using a low gain ink would't that open up the G7 gamut? I am thinking that less tonal compression because of dot gain compensation would effectively increase the number of colors within the boundaries of the color space.

G7 is a grey balance process, not a profile or a color space. It doesn't have a gamut.


Mike Adams
Correct Color

 

[Stephen Marsh]

G7 is a grey balance process, not a profile or a color space. It doesn't have a gamut.


Mike Adams
Correct Color

http://www.idealliance.org/specifications/gracol/g7-vs-gracol

I believe that G7 now has a “wider context” than the original gray balance based calibration method.



Stephen Marsh

 

[aqazi81]

If you decrease the size of the halftone dots that are used to simulate tones then there will be more ink dots per area and hence more opportunities for light to be filtered by the ink and less light reflecting off the non-inked area of the substrate (that unfiltered light effectively reduces gamut). That's why FM screening does not increase gamut - it just reduces it less that a coarse AM screen).

Correct me if I am missing something here,
You said that FM screen does not increase the color gamut, but on your blog you mentioned that 20 micron FM screen provides 10-15% greater gamut.

And 1 more question...
Why the dot gain has no effect on color gamut?

 

[gordo]

Correct me if I am missing something here,
You said that FM screen does not increase the color gamut, but on your blog you mentioned that 20 micron FM screen provides 10-15% greater gamut.

And 1 more question...
Why the dot gain has no effect on color gamut?

Correct - FM screening (typically 20-25 micron) has a larger gamut than AM screening (typically 175-200 lpi). When AM screening gets to about 325+lpi the dot size and distribution approaches 20 micron FM and so at that lpi the AM screening gamut becomes similar to 20 micron FM.

You see color because light is filtered by passing through a film of ink.

When you look at a printed area you are looking at the combination of light that is filtered by the ink and light that is just reflected off the sheet that has not been filtered by the ink.
If light does not pass through the ink but just bounces off the white paper it effectively contaminates the color - it greys it.

If the ink fully covered the sheet (as in continuous tone lithography) then all the light would be filtered by the ink and you would have the maximum gamut.
Because, for a given tone value, more light is filtered by an FM screen the gamut reducing effect of light bouncing off blank paper is less than with an AM screen. So, the potential gamut is reduced less by an FM screen than with and AM screen.

So, because FM screening reduces gamut less than an AM screen the effect is that the FM screen gamut is larger than the AM screen.

Dot gain is also called Tone Value Increase. Tones are degrees, %, of light and dark not degrees of Chroma/Saturation as far as gamut is concerned. A 100% patch of, for example, Cyan represents the maximum chroma/saturation in 2D space. Where FM screens provide extra gamut is in the tones between about 20% and 80%. So, for example, a 40% 20 micron FM Cyan patch will have a higher chroma than a Cyan 40% 175 lpi screen even though they measure as the same density/tone value on the press sheet. The hue (angle) will also be different. The hue of a Cyan 40% 20 micron FM patch cannot be matched with a 175 lpi screen. However, the hue of the 40% Cyan 175 lpi screen can be matched by a 20 micron FM screen by contaminating the FM patch with Black and Magenta or Yellow.

The extra gamut in the tones between about 20% and 80% for an FM screen is seen in 3D gamut plots and can be seen in presswork. When I was at Creo/Kodak we distributed press sheet samples to demonstrate this effect.

You can see a video of the gamut differences here: http://the-print-guide.blogspot.com.au/2009/03/am-and-fm-gamuts-compared.html

I hope this makes some sense.

 

[Morgan Manning]

PM me if you want to chat about it (being I know your specific process and consumables)

 

[Green Printer]

From the information presentted as spaces between the pigments particles in the ink film approach 0 the number of colors that are reproduced can be changed within a pigment set. I think that this is possible no matter what the AM or FM spot size.

 

[Alois Senefelder]

Gemtlemen and Green Printer,

Salient Points - without going into the realms of infinity and pigment particle size re - colour gamut,

more important is the Refractive Index of various paper grades and the role it plays

in colour reproduction.

Regards, Alois

 

[gordo]

Gemtlemen and Green Printer,

Salient Points - without going into the realms of infinity and pigment particle size re - colour gamut,

more important is the Refractive Index of various paper grades and the role it plays

in colour reproduction.

Regards, Alois

Somehow I don't see the importance of the speed of light variation through different mediums as being a factor influencing gamut. Are you sure you mean "refractive index"?

 

[Alois Senefelder]

Gordo,


We need to remember that a sheet of paper is just a "Mat of Wood Fibres" made from various Soft/ Hardwoods, which when pulped produce

different fibre lengths so each have a different refraction.


Regards, Alois

 

[gordo]

Probably not in this forum, it isn't.

Perhaps it wasn't made clear.

Yes it is possible to increase color gamut with a low dot gain ink.

Originally posted by Green Printer:

Is it possible to increase G7 color gamet with a low dot gain ink?

But the original question had qualifications which needed to be clarified:

"G7" is not relevant because it is a grey balance method - nothing to do with gamut.
"Low dot gain ink" is also not relevant because dot gain refers to tonal reproduction - L* - which is not gamut.

 

[Alois Senefelder]

Colour Gamut/ Low Dot Gain Ink


Hello fellow Lithographers,


Answer - Have the plates imaged using production compliant reproduction, not

relying on Witches'Brew i.e. Low Dot Gain Ink.

Definition: Witches' Brew, a concoction of strange, powerful or terrifying ingredients.


Regards, Alois

 

[Green Printer]

I have never heard of a technology being called witches brew.

 

[Green Printer]

Perhaps it wasn't made clear.

Yes it is possible to increase color gamut with a low dot gain ink.



But the original question had qualifications which needed to be clarified:

"G7" is not relevant because it is a grey balance method - nothing to do with gamut.
"Low dot gain ink" is also not relevant because dot gain refers to tonal reproduction - L* - which is not gamut.

Gordo thank you for the clarifications.

 

[Green Printer]

Gordo

Is there any recommended dot gain you want to achieve for the G7? Or do you just adjust the curve to arrive at the proper delta measurements. and the curve is what it is.