Message
Re: The limits of working with QTR
2017-09-03 by skapuskar@...
A friend of mine asked me to help him out creating a profile for negatives to be printed on silver gelatin paper. To be honest, not my way of printing silver gelatin, I'm an old fashioned guy still preferring printing by hand under my enlarger. Anyway, I took it as a challenge. The advantage of experimenting with digital negs for silver paper is the fact that process parameters can be kept very consistent (same developer, temperature, same light source, I have a cold light enlarger with light probe and compensating timer), and the DR is quite low, around 1,0 D, so ink deposit limit on OHP is easy to control.
My base curve is a straight line array, composed of the most blocking inks for the specific process, obtained with the QTR calibration pattern. Somehow I have been getting better results with this approach than cross-over ink profiles. The difficulty is always getting good separation in the last 20% of the highlights, hence my initial post about problems with self-masking within the carbon process and paper inertia in the case of silver paper. The need of a K or Toner boost seems mandatory for me to obtain a clean white and fair separation between 5-10-15-20% of the highlights. This is what I'm talking about regarding 'smoothness' in my previous post, it is not about ink pattern grain, I'm quite happy with what I obtain so far.
When I mentioned the limits of QTR, it is because it can not take into account the S-curves of silver paper/alt-processes, their initial inertia to exposure, self masking of sensitizer concentration, etc., may others chime in with other process properties :-)
I always end up having to tweak the final result manually.
Grey curve first, then Linearize command, or the other way around?
I have tried both, resulting in two different curves, both worked pretty well.
Preference was grey curve first, then linearization.
I believe it is simply impossible to have a software to create that perfect profile for any alternative process, so manual (human) tweaking is necessary, and I like that idea.
For my carbon work, for example, I do all my calibration with a 2% dichromate solution, creating a grey curve with my densitometer values in QTR - then new test print and linearizing output for the final profile.
In the end, the most pleasing result I get, is printing the same profile with a 1% dichromate solution.
Sidney