### Digital Negative Issues
Sandy, you can use the gray highlight, shadow, gamma, and curve settings if you set it up as single partition profile with the only gray inks as the K channel. You could still have the other inks copy the K curve, and then print a 21-step target (including the copy curves) and then linearize with my correction curve tool for digital negatives in the gray curve setting. At that point you wouldn’t need the QTR linearization. The problem with using copy curve is that the blocking density for each point on the curve isn’t always consistent from one ink to an other. In your set up it would be better to use LK as toner 1, and yellow as toner 2, and then linearize each separately with the toner curve setting. The K channel is then linearized with the gray curve setting, and then you could linearize all three inks together with the qtr linearize= setting. I am not sure if it is a good idea to run a heavily dithered full dilution black in the highlights, so I would recommend having a LK/K grayscale partition with increased overlap, and linearized with my gray curve correction tool. Then run Y separately a toner partition linearized with its own toner curve.
I’ve also played with the idea of using a two-quad curve system that is blended in the print settings to produce more blocking density depending on the needs of process/chemistry mix. One quad curve is with a single linearized K3 partition and then another quad curve with a linearized K3 partition and a Y toner curve much higher Y limits. You blend in the quad curve with the yellow toner with higher limits and everything stays (more or less) linearized. I dropped messing with all that when I moved on to the next thing using Piezography inks…
Paul, transparency material is definitely not all the same when it comes to the amount of ink it can accept. You would find that too if you tried putting as much ink on their as Walker’s system does. Over the winter, and as a bit of a personal challenge, I built my own system of using 6 piezography inks (both the straight K6 set and the old set with shades 2.5 and 4.5), and a way of hand shaping the QTR curves to create more overlap similar in shape to the Piezography curves. From there I had to build my own system of linearizing 51 and then 129 steps in the negative (I only used the QTR tools to get the initial partitions, and then shaped everything from there using tools I made in excel). Then I tried the new PiezoDN system when it was released. Walker’s linearization system is much easier than building your own, which is partly why I never posted more about it… I tested both ways with all three transparency materials. Only UltraPremium OHP could deal with the ink load from 2-4 inks for ever point on the scale. InkPress and non-Ultra Premium OHP were just not capable of handling the ink load and resulted in mottling—platinum and gelatin silver. As an aside, they PiezoDN system works pretty well with Azo/Lodima Grade 2. Things have been really busy and I haven’t been able to do all that much with it, but will put some serious effort into writing more about it when the new batch of Lodima is a ready later in the year.
Paul, the overly simplified approach to digital negatives (like single K channel and CopyCurve) is why people have so many problems and never arrive at anything with the level of accuracy that something like the PiezoDN system is capable of producing. If the concern is being able to adjust for variables in paper and chemistry, the PiezoDN system makes incredibly easy as well. If someone was REALLY invested in not buying the Piezography inks/system then there is a way to hand their own blend inks and come up with their own partitioning and linearization system to get the same results… It might take a few months of work but it is doable…
Hope that helps,
Richard Boutwell
http://www.richardboutwell.com/
http://www.bwmastery.com/