Creating QTR Profiles from "Plot Lists"
2007-12-04 by Louis Dina
I promised to provide some feedback on building QTR profiles using the "Plot List" feature, where you can design your own curves. Paul Roark has been doing this for some time, and I owe him a big thanks for all his guidance, both on and off forum. I find this method has a few distinct advantages. Advantages include the ability to control every point on any individual curve, including where the ink starts and stops. My original reason for trying this method was that I noticed that my finished profiles usually had a density loss of 0.03 to 0.05 in terms of Dmax, and I determined that this was due to the introduction of light inks in the shadows using the standard QTR curves (I am using the MIS Pro color inkset on an Epson 4000, so I use LC, LM and sometimes other colors to control the tone at different points. This does not provide the same light fastness as pure carbon profiles). Anyway, a density loss of 0.03 to 0.05 may not be a big deal on papers with a high Dmax, but it can sometimes make a big difference on many of the matte fine art papers. So, I stopped the use of light inks at about 95% and the density came back up to the Dmax the MK ink showed on the original calibration target print. Also, by trial and error, I was able to create nearly linear profiles prior to linearization, and the final linearization simply applied small corrections to make it nearly perfect. The biggest advantage to me is the ability to copy these profiles to new papers, requiring only that I set a new ink limit (which readjusts all inks in the profile), followed by a linearization. This can also be done with QTR profiles created in the standard manner, but this I preferred this approach. The biggest disadvantage is the substantial time and effort required to set up the original set of curves using plot lists, which was quite time consuming and a bit tedious. <b>(It sure would be nice if we could edit curves on screen by dragging and dropping points on the curve or using the arrow keys....hint, hint.)</b> I was originally hoping that I would be able to use my original matte profiles (designed for warm toned fine art matte papers) and repurpose them for use on luster and glossy type papers too. Setting ink limits and linearization work great.... but.....the PK ink is a LOT (and I mean a LOT) warmer than Eboni black, so all profiles created for glossy and luster papers from my matte profiles tend to be a lot warmer. So, I am in the process of creating a set of "Plot List" profiles for those papers that use PK ink, (Ilford Gold Fibre Silk, Epson Premium Luster, Kirkland Glossy, etc), and will use them as the basis for building new profiles on other similar papers. Just setting the paper's ink limit and relinearizing should be all that is required. The standard QTR curve shapes work fine and are a lot less work. But the use of Plot Lists can provide extra control where desired, such as building a single split tone profile (which doesn't require blending two or more profiles). It also allows me to improve Dmax in the deep blacks. You can do nearly anything you want with plot lists if you have the time and persistence. Since I am not using Quad type inksets, I cannot comment on whether this approach would show any improvement over the standard approach. I suspect there would be less difference, since you are usually using 3, 4 or more shades of black for the curves, so any "pollution" of the deep blacks would seem to have less effect on Dmax, since it would be a darker ink to begin with. Paul or others will be a better source of information on that subject. As porky pig says....ah-ba-dee, ah-ba-dee....that's all folks! Lou