Hi,
I have been trying to make my own QTR calibration files. By investigating the existing ones I found out that the magic of the calibration happens in the Red and Green channels while the Blue channel is empty/white.
The red channel defines the ink density layed down. In the 6, 8 and 10 inkseparation files this is represented by 6, 8 or 10 normal stepwedges with 5% intervals in density from 0-100%.
The Red channel seems to define what ink is used. This, as far as I have understood, is not the actual K percentage but the (3x identical) RGB value. Where the K is represented by R127 G127 B127, C=> 191, M=> 223, Y=> 239, LC=> 247, LM=> 251, LK=> 253, LLK=> 254. Last one is also used for gloss optimizer on printers with GO.
There's also the inkseppatch.psd file that has all the individual inks as 100% patches and 2 and 3 ink combinations. They come each with their own RGB values. The G channel value is also changed when 2 or 3 colors are mixed. It changes from 100 to 50% for 2 inks or 33% for 3.
That's where my understanding of the underlying principle takes a halt. Are the RGB values for the individual inks and the 2/3 ink combinations from inkseppatch.psd hard coded in the software? Are other combinations possible. Can I make my own mixes of inks for calibration. I was interested in making a CY patch for example but could not figure out how to do that.
Kees