QTR-Quadtone RIP

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Most K inks in OEM sets are primarily carbon with maybe 1% of colorants from ink batch to ink batch so the color is stabilized to the original 100% carbon ink (in Epson's case they stabilize to Ultrachrome K2 introduced into the 9600 and I think they have added a LOT of colorant to their LK and LLK inks of late). Carbon is always warm, however, to varying degrees based on particle size. A glossy ink (PK, LK, LLK) is quit warm because the particles are smaller. The larger and more opaque the particle size (MK ink) the less warm the carbon will be.

Tldr: black only ink from epson, etc, is going to be warm. Cyan and Magenta (and basically only these colors + their lighter versions) are needed to neutralize this ink in ABW or QuadtoneRIP, etc.

Related to thread topic:
Look very closely at ABW with a microscope and you will see a few yellow dots in there though. And also, ABW is using color dots to soften the noise attributed to using only 3 black inks. There is no way to not use color ink when printing ABW even when choosing a color tone that is closes to the pure black warm. A side benefit of 3 warm black inks is that you can print color inks (more nozzles) to neutralize the print and also decrease overall noise of the print. This was most relevant with K2 inks ets and might have even been a feature of those early printers: aka, how they got by with so few nozzles.

Related to measurements:
Also remember that paper white and paper chemistry effect the AB measurements as well as the ability of the device to actually properly read AB values at low light reflectance (darkest patches). Accuracy is relevant to these conditions.

Related to neutral as discussed below:
Yellow is not needed with carbon K inks + C Lc M Lm ink sets in order to get a neutral print. It’s only needed if  you need to make azzo green type colors. I think Epson puts an unnecessary amount of yellow in their ABW prints. QTR generally does not use yellow at all and this is preferable for archival reasons.

Best,
Walker



> On Jun 12, 2018, at 2:58 AM, claudebou777@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> Some months ago I did extensive tests printing the usual 21 wedges on Epson Archival Matte paper with my Epson R3000 printer equipped with regular Epson inks MK, LK, LLK.  I used lab b* as an indication of the neutrality/warmness of the prints.
> 
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> The Epson ABW driver with settings  "neutral and dark"   and H=0, V=0  gives slightly negative lab b* values while H+3 and V+3  a bit above the line.  These measurements are fairly similar to those obtained with my custom neutral QTR curve using all 3 gray inks and LC (light Cyan) + LM (Light Magenta).
> 
> Beware that the prints can be very warm even without presence of yellow like when using QTR curves with solely the 3 gray inks.  The only evidence of use of yellow I could find is in the article of Gorgio Trucco who posted microscope images.
> 
> Since I am not selling prints,  I currently consider my prints obtained with the ABW driver and the above settings as a reasonable neutral reference under controlled lighting . They render a bit warmer under most domestic light.
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