QTR-Quadtone RIP

Dear list. This is related to the thread and pertains to linearizing for darkroom negative printing (something Richard just mentioned.)

We have built a system we are calling PiezoDN for Piezography using QTR that lets you linearize a negative .quad yourself directly from darkroom-printed patches using Roy’s linearizer. This is also then accompanied by a Create-ICC grayscale profile that does a final Perceptual linearization of the negative to match contrast between screen and print (optional).

We are calling this system PiezoDN and will be selling install packages for the curves/iccs starting with curves for Palladium and Potassium Oxalate printing (on BerggerCOT320,HahnemuhlePatinum,ArchesPatine,LegionRevere) but eventually hope to calibrate the history of analogue from silver/salt/cyanotype/gravure/etc. Launching for 1430/3880/4900 printers in the coming weeks.

What we have done is build a brand-new internal profiler and master curve builder that makes master curves for each alt-process to the desired contrast ratio (dmin to dmax) required by the light-sensative material. Our resulting master curves are so linear when printed with K6 and GO that they are essentially ready to go. The linearity is archived by a relationship between the ink chemistry and dMIN curve shape and dMAX curve shape + underprinting characteristics that went through about 700 iterative changes to achieve dMAX and paper-white dMIN for any given process/printer using a single sheet of OHP UltraPremium film.

 If different darkroom chemistry is being used, these curves can be simply tuned with Roy’s linearizer and then iteratively tuned/profiled with Roy’s create-icc.** In most cases one only has to build a create-icc or simply use ours if their chemistry and workflow match what we had during the R&D of the curve/profile. For brand-new processes, PDN works perfectly still to do photoshop limiting of the density but we can also build custom limited and linearized 256 patch masters directly off customer’s alt-process work if the negatives they are printing are too dense for their process. Or, a simple straight-line Photoshop curve can be applied to a target patch set and then applied to all images printed from the resulting calibrated .quad or ICC (Both PDN and straight-line limiting diminishes bit-depth in the image. This is partly why we built PiezoDN.)

The smooth piezography master curves for negative printing were calculated at 2x to 4x the bit depth of normal .quad linearizing (and then iteratively refined with 256 step prints.) We have spent nearly a year building and fine-tuning the internal profiler and master curve maker that lies at the core of this new negative-printing process and adds to the long history of Piezography and fine-art printing.

This system uses shades 1-6 (no longer needed are shades 2.5 and 4.5). For pro printers, it also does dual Gloss Optimizer printing (at 10% to 20% or so) for added negative durability (very important).

We will be launching this system soon, but it’s working in-lab currently for Palladium and we are teaching it starting this spring and throughout the summer.

This is a small screen-shot that I did today of a linear Palladium step print result graph that we are using to build a 129 patch Create-ICC profile: facebook dot com /greendirt/posts/10154141435327220

cheers and happy darkroom v2 printing,
Walker

**as long as one has an i1 or other spectro.


> On Apr 14, 2016, at 10:20 AM, richard@richardboutwell.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> The at is partially correct. The curve creation program that is run when "installing" an ink descriptor file is a black box. All the partitioning formulas and gray curve adjustments can't be seen because they are all just executable binaries that are called at different times when installing the profile. I guess if you were a hacker type you could get them out of there some how...
> 
> 
> Edibility of quad curves: there have been a number of threads over the last few years that have gone into this, and a few people have worked it out with different kinds of spreadsheet methods. All of that was not for the feign o heart and was before Roy released the linearize-quad app. That works well for a lot of users, and is the first thing that should be used. 
> 
> 
> All that being said, for the past few weeks I have been working on a way of taking the individual quad curves for a linearized profile and parsing them into 21 steps so I can manually adjust the shape of the ink curves in Excel or Photoshop to get smoother shoulders and long trailing edges (while still maintaining the same ink load). I then put them back into an new ink descriptor file as Curve_ink="0;0 5;25 ... 100,0 " or ACV curves made with PS (and then change the limits to 100 for each of the inks used so the ink load in each of the curve stays the same), and then using my own linearization tools to fine tune the final linearization. I have all that figured out for inkjet positives on paper, but doing the same for digital negatives is what has me hung up now (well, 21 steps is easy, but refining with 51 to 218 steps is a little messy still with digital negatives). 
> 
> Hope that doesn't muddy the waters too much 
> 
> Richard Boutwell
> 
> 
> 
>