I have been using QTR and QTR Print Tool for a few years on a Mac for making printing profiles for digital negatives used for carbon transfer. I've been very happy that there has been such an effective tool for crafting digital negatives using standard inks. Sandy King has continued to develop his profiles and share them with fellow carbon printers, and the methodology has become better and simpler.
My current question is about the linearize function built into QTR. This looks like a very effective tool for creating my correction curve and getting a perceptually correct distribution of my print tones.
However, there isn't very much documentation on how the function works and I have a few questions:
1. I have had trouble keeping a reliable densitometer on hand and I would like to be able to use my v750 scanner to scan my step tablets and then measure my actual print values as well as nominal values from a calibration strip into the function. Is there a procedure for getting values I need to enter into linearize without using log values from a densitometer? I came across the QTR step wedge tool and script in the files section. However, I would like to have a manual procedure I can use. Without pouring through the script, I am in the dark as to what the script is measuring from the scanned file and how these values are manipulated. I would like to have an understanding of how to use linearize using a scanner and photoshop.
2. I read somewhere that these needs to be a minimum spread between each of the steps in the tablet that is read and entered into linearize. What is that value? Like a lot of alt processes, my shadows are quite blocked up without and adjustment curve. Should except to adjust my negative before using Linearize?
3. Are there any tricks or tips to using the output for negative vs positives? I saw somewhere that the function can create a "digital negative" output where the order of the values is reversed.
Is this only difference in using Linearize for negatives?
4. What does the Linearize function do at a high level. How does it spread out the values and create a perceptually uniform spread.
Any help is appreciated!
Thanks,
- John