Question about Limiting


#1

On p. 108 of the PiezoDN chapter, The Piezography Manual says that limiting is needed if your process “requires a thinner negative than you would get using a pre-calibrated curve that comes with PiezoDN.” The 27 steps that follow are designed to decrease the amount of ink used in the highlights.

But what if my process requires a thicker negative than the one I would get using a pre-calibrated curve? Can this also be achieved through limiting? Or some variation of the limiting process?

I have posted elsewhere in this forum about my three failed attempts at linearizing New Cyanotype starting from the pre-defined cyanotype curve. This post is really about the manual, and whether the manual has omitted the case of when a thicker negative might be needed.

 


#2

In a nutshell, the curve named [printermodel]-PiezoDN-Master.quad is the starting point for any process if you are going to build your quads from the ground up which I strongly recommend. It is very unlikely (but not impossible) that your process will require a thicker curve than this. Yes they provide starting points for certain specific processes, but they may or may not be good starting points for anyone else. You have to try them to find out. In the ReadMe file that is in the folder with the curves they give process details for each of the curves. The cyanotype curve says “1:1 mixture of Ferric Ammonium Citrate & Potassium Ferricyanide.” Even this is incomplete though since it leaves out the % concentrations. But it’s clearly not the Ware formula since it’s 2 solutions, and it uses FAC rather than FAO.

One thing that would be useful for purposes of trying to match your process to a pre-defined quad curve for a starting point would be to include the Exposure Scale (ES) of the process. This can be determined easily from a print of the Stouffer 21-step. (I use the 4x5 version.) I’ve been using this tool as part of my darkroom process for film development and all printing processes since 1991. I would feel lost without it. For example, I mostly print straight Palladium developed in hot potassium oxalate. For the specific way that I do things, the ES is between 1.8 and 2.0 for most papers. For the paper I’m using on my current project Gampi Torinoko, it is 1.8. I’ve recently been using the Malde-Ware POP method with Pd humidifying the coated paper to ~75% before exposure. This method has an ES of about 2.15 for Gampi Torinoko. I had to relinearize for this process change, and I began from my own custom limited “Master” quad. Alternatively, I could have started from the IJM Master.quad.

Classic Cyanotype (CC) generally has an ES of about 1.1 which is quite low. In other words, the process itself is very contrasty and thus needs a low contrast negative. Mike Ware’s New Cyanotype (NC) is much closer to the ES of Pt/Pd. Mike says its ES ranges from 1.8 - 2.4 depending mostly on paper. I found it to be more like 1.6 - 2.0, with most papers I tested being 1.7 - 1.8, but this is at least partially due to interpretation of the data. (That is another topic for another time if anyone cares.) My point is that using the IJM cyanotype curve, which is for CC, for the NC process ain’t gonna work. I’m sorry I missed this in your earlier threads. You probably mentioned it somewhere. One of the supplied Pt/Pd curves would have been a better choice to start with, though I would have advised using the PiezoDN-Master.

If I was teaching a class in alternative process printing, ideally in the first semester we would do nothing but print Stouffer 21-steps. I know that’s a little extreme but I did say “ideally.” :wink: How about for the first few days with each process?