Message
Re: Help with Single Gray QTR Profile
2017-02-22 by sanking@...
The first test I made for the single gray value system was to print an inkjet separation 8 file in QTR calibration mode to determine the relative UV blocking of each of the inks in the K3 ink set. Initially I determined the relative values by measuring the densities with a UV transmission densitometer, and with that instrument the cyan in the K3 set measures high in UV blocking, about the same as the PK and Y, so I set all three to 25%. Later when I tested the calibration page with several alternative processes I found that the C is really a very low UV blocker, no better than the M, so I now treat it that way and set the ink limit to 1.
My view is that one should zero out readings to paper white. Not doing so will alter the grade/slope of the curve, which in turn would change the density at 50% where the correction is adjusted to linear. The difference cold be very small and have no practical impact on results, or it might be quite large.
Sandy