From: Alastair M. R. <bla...@fa...> - 2009-03-31 17:46:10
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Hi :) Robert Krawitz wrote: > I remember that, and I would like to do the same thing. There are a > couple of specific per-channel things I would like to do, though: > > 1) For the printer channels, plot density for each individual drop > size to more accurately calibrate the drop sizes. That's something I've been meaning to add to GPLin - not got there yet, but I'll make it the next priority if it's going to be useful. It shouldn't be too hard - just a case of printing an Argyll target using drop-size segmented dithering, then interpreting the results. > 2) For each subchannel, plot density to determine relative density > (value) for each subchannel and to determine where the density > stops increasing linearly (to help determine the transition). Rather than use traditional density measurement, for GPLin I'm working in terms of L*ab. What surprised me is that the L* component, which I'd considered the analogue of "density" seems to tell less about paper saturation and ink limiting than the colour components. As the ink coverage increases, a plot of the a and b components shows a significant drift in hue, which isn't easy to see with the naked eye. http://blackfiveimaging.co.uk/linearize/gplin_ab.jpg GPLin uses this drift to choose its default ink limits for colour channels - though of course it has to use a different method for black. I'll be very interested to learn whether the current method gives sane results for printers with more than one black channel! Again, the ability to analyze subchannels and give relative proportions isn't yet implemented, but again, I can make this a priority if it's going to be useful. All the best, -- Alastair M. Robinson |