A quick update for anyone following this conversation, or coming to it later…
I’ve had a chance to print with adapted versions of Paul’s “generic” curves on three papers, all by Premier Art. The papers are Smooth Fine Art 325 gsm, Fine Art 205 gsm, and Smooth Bright White 200 gsm. All three are cotton matte papers.
My workflow is based on Windows 7 and Lightroom 6, with TIFF files created for Quadtone RIP. I discuss this workflow in a posting on the QTR forum (https://groups.yahoo.com/neo/groups/QuadtoneRIP/conversations/topics/13420).
For each paper, I used Paul’s generic curve as a starting point to create warm and neutral curves. On the unbrightened papers (Smooth Fine Art 325 gsm and Fine Art 205 gsm ), I usually start by making a test print with the neutral curve, and then I add in the warm curve as needed. On these papers, the neutral curve is to my taste most of the time. On the brightened Smooth Bright White 200 gsm, I find that the neutral curve can be a bit too cold, so I’ll usually split tone with the warm curve, or simply mix it with the warm curve.
On my calibrated monitor, I’m finding that images print consistently across the three papers. I tested to see if I’m getting a smooth tonal range.
In a bullseye test, there should be no breaks or steps; in this respect it could be a bit better. I can detect ever so slight unevenness in a few places. If there’s an impact on real-world images, I can’t see it.
I tested using Keith Cooper’s black and white test image
(available here: http://www.northlight-images.co.uk/article_pages/black_and_white_test.html).
If a curve prints that image properly, then I'm happy. (At the link above, Keith provides detailed notes about how the printed image should look.)
Finally, just to be thorough, I also tested with a 256 step chart (where 0 is dMax and 255 is paper white) to see if I’m getting a full tonal range. I did this test only for the Fine Art 205 gsm curve. Using my spectro, I’m able to easily distinguish each test patch from its neighbour. In practical terms, this means the curves can represent all the detail that exists in shadows and highlights.
I’m very happy with this setup and want to thank Paul Roark for making it available. Yes, the blue and cyan toner inks are expensive in the cartridges that Paul identified – but it’s worth it to me to have the kind of simplicity and control provided by this inkset and the curve.
Most importantly, I think this approach is a great way to get people started with carbon on cotton printing using Quadtone RIP. Many users may be perfectly happy with the results they can get by adapting Paul’s generic curves. It’s still not quite a “turnkey” system, but it’s certainly much easier than starting from scratch.