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QuadTone RIP

by
Jon Cone
published on 12/22/2009 19:00:00

BACKGROUND

There are two RIPs which support Piezography inks. The ErgoSoft StudioPrint RIP (SPR) is expensive and very full-featured. It has enormous flexibility at a high cost. The other, QuadTone RIP (QTR) is inexpensive ($50) and because we produce the media linearizations for it with our own Piezography software – the output quality is actually higher. We use both products in our studio. We run QTR to produce all single ink set prints including our glossy prints. We use SPR to blend between two or more ink sets.

QuadTone RIP by Roy Harrington is based upon open-source code and we embraced this concept after our way to early for primetime ICC based Piezography BW ICC system of 2003. In 2003, we had invented an ICC profiling system for monochromatic ink shades that used the Epson RGB driver. But, the average consumer did not understand how to use ICC profiles, or began to mis-apply the workflow necessary to produce proper color management. ICC workflow is much more mainstream these days, but open source software is much more mainstream than ICCs which depend upon the OEM’s printer driver.

About 2004/2005 we began to look seriously at QTR. The QTR is an individual ink jet head printer driver. QTR is able to control each individual ink jet head. QTR uses a system of curves to manipulate a grayscale image file. It uses a curve for each ink jet head. Because a different shade of ink is associated with each ink jet head, a different curve is necessary for each shade of ink. These curves are grouped together into a file that is (still called a curve.)

We tried to use the QTR tools to make “curves” (a profile in QTR) and found that that the tools were suitable for making 3 and 4 shade curves. But, to make 6 and 7 shade curves that would be suitable to our next generation 6 and 7 shade inks…well it was just not possible to reach the standard that we had delivered with PiezographyBW ICC.

I always want each new generation of Piezography to be better than the one before. PiezographyBW ICC was a quantum leap in quality and functionality over the PiezographyBW plugin. We believed that seven shades of ink (K7) would dramatically improve the output of the ICC based system that used only 4 shades of PiezoTone inks. My answer was in developing a QTR profiling application. We developed in-house (as usual) a profiling app that can linearize up to 8 ink channels and output a QTR compatible curve set.

We use the application (we call Barney, or sometimes The Piezography Profiler) to create curve sets for each of our supported printers. These curve sets are for a core base of popular papers. When we complete a new edition we send these curves to Roy Harrington who incorporates these curves into his QTR software. We do not charge the customer for these curves. We do not charge Roy for these curves. When you download and install QTR – these curves are installed automatically into your computer and will be available for your when you operate the RIP. We do make custom curves for those who wish to use media we do not already support, or wish to have their aging printer linearized (rather than freshening up the printer by replacing worn print heads). But generally speaking, when you download QTR for your Piezography supported printer – you have a turn-key system.

This is what I am doing behind the scenes to make your Piezography experience a magnificent one!

CURVES ARCHITECTURE

The anatomy of a curves structure is related to how much total ink the paper can absorb, what is the combination of shades that will produce the deepest dMax (its not black alone), and the amount of ink shades that need to be structured, overlapped and feathered in and out without leaving any sign of their presence. I create a curve structure based upon using as much density that is practical on the lightest shade first. As I feather in the second ink it affects the shape and height of the bell curve of the first ink. I have a method that lets me rough in this process quickly – but it takes several days to make a set of curves that on their own are near perfection.

An algorithm is used that smooths the curves (although the process actually roughs them up a bit.) And the end result is that by measuring 255 printed patches of ink and the paper white, the algorithm is able to produce a perfect linearization from dMin to dMax. The curves are then plotted at 256 locations each curve, choosing the appropriate point out of more than 64,000 levels – in order to combine together into one media profile.  A media profile is made for each of the papers we generally support, and these are made available to the author of QTR who then includes them in the installation package. It is possible to order custom curves for QTR. We supply the 256 patch target, a special Master Curve, and a set of instructions to follow. The charge as of this writing is only $99 each.

Here is the link to downloading QTR for Piezography. Please pay your $50 shareware to the author.

Here is the link to our manual on using QTR. We do it a bit differently than the way it is done in the manual supplied with the download.

Below is an actual curve for QTR made by the Piezography profiler for the Epson 2400 printer, K7 inks and Hahnemuhle Photo Rag paper.

A Piezographly media profile as seen by the QTR Curves Viewer