I have a few B&W alt process photographers in my area and some who have asked about whether the glossy carbon inkset I've been using lately would be suitable for alt process internegatives. So, I've tip-toed into the arcane realm of alt process to see if I can help my friends simplify and maybe rationalize their (rather SOP now) workflows. Time will tell. I do not anticipate participating in wet darkroom work myself.
These are some very preliminary thoughts that need to be taken as such.
My first conclusion is that the glossy carbon inks I use will work just fine. However, OEM k3 inks also are just fine.
The local alt process photographer/gallery owner uses a 3880 with OEM inks. So, that is mostly what I'm looking at. However, my experiments with my carbon inks and the 3880 OEM inks suggest that the same concepts will apply to both, with the obvious roll of the yellow ink missing in the carbon ink situation.
The alt process we're now focusing on is based on the Bostick & Sullivan platinum emulsion chemistry. Exposure is via a metal halide broad spectrum light. This measures its own light. So, one just dials in a number and the light does the rest. Currently the basic exposure (dmax reached through the film base) has been set at 24, but as the scan fo the final print (link below) shows, it's not quite on the mark yet. The exposure outside the film base is slightly darker.
That said, the scan of a QTR Calibration Mode print on Inkpress film and then contact printed on the platinum print paper is close enough to see what is going on. Below the scanned image I have the Excel graphs of the PK, LK, LLK and Y inks. The graphs are up to "50%" on the Calibration Mode print, but have as the starting point the paper outside the film base.
http://www.paulroark.com/BW-Info/QTR-Calibration-Mode-Platinum-3880-24.pdf
From what I've seen so far, I am going to recommend the M and C colors be ignored and not used. Frankly, the hand coated paper is so rough that the fine details we worry about in inkjet printing on coated papers are of little concern. No dots or microbanding are ever going to show (and the 3880 with OEM inks is so smooth they don't show in normal printing either). At least for the platinum printing like this, we don't need many inks.
The yellow has essentially the same UV density as the PK. (I do not know exactly what the B&S chemistry spectral sensitivity is. So, this may vary with the emulsion type and mix.)
With the Yellow in effect the same as the PK, I will probably do a "copy curve" from the PK and cut the ink limits in half. The boost, however, only affects the K. So, whatever boost is settled on will apply only to the PK.
(An alternative approach that I like for normal printing and might take here is to use the yellow as a separate toner channel, with density 100 so that it becomes a "black only" type of curve. This can then be taken manual and be a way to get the pre-linearization curve essentially perfect. But this is a bit further down the road.)
My early profiling on Pictorico White Film ("PWF"), then printed on Inkpress film and scanned with a Nikon 8000 to see what the transmission densities looked like, suggested a potentially interesting approach to transparency profiling. The PWF profiles used to print on the film produced films that looked way too light. Of course, with a reflective print the light goes through the inkjet coating twice -- once to reach the paper, then the reflection back to our eyes. So, the transparency is about half the density of the reflective media in the midtones. Then near the 100% black end it dives in a very non-linear fashion to the black point.
What largely offsets the printing differences is to simply alter the PWF profile gray gamma from the default 1 to gamma 0.4 for the transparency. To offset an un-wanted flattening of the K curve at the end, there should be a boost of at least 10 for the K. That is, if the ultimate K ink limit was 50, set the K limit to 40 and boost to 50. Then the transparency became quite linear even before linearization, (which I am currently thinking should not be done at all at the internegative stage).
There are so many variables in the alt process workflows, that very simplified QTR profiling would seem to be a benefit for that group. Whether my outsider's look is useful remains to be seen. Those that wander into the alt process realm have my admiration and sympathy.
Paul
PaulRoark.com -- Paul Roark's Photographic Home