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QTR-Quadtone RIP

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Adding tone to basic 3 ink curve.

Adding tone to basic 3 ink curve.

2016-04-11 by mattbaily@...

Hi all,


Can someone help me out and provide a workflow guide for adding tone to the basic 3 ink ultrachrome curve. I have created an all grey custom curve via the usual quadtone rip workflow ( find ink limits -> set ink cross over -> linearize curve ). It looks pretty good. I now want to add some tone to neutralize the greenish hue. Can someone provide a set of steps to achieve this? I understand that I need to set ink limits for the magenta and cyan color sets and then create cross over points for each. My question mainly lies in what defines those color ink limits. From looking at a bunch of ink descriptor files, it seems they are very lower than the actual max, which makes sense as you would not want to add much colored ink, but how are those values chosen? Trial and error? How does the addition of tone effect the main grey curve - with the addition of the color ink do I have to adjust it and lower it's ink limit to prevent too much ink lay down?


Thanks,

Matt


Re: Adding tone to basic 3 ink curve.

2016-04-11 by richard@...

Hi Matt,

The limits for the toner inks are based somewhat on the color of the paper base and some trial and error. I found a good starting point for a neutral tone is about 3-5 cyan and 4-6 magenta, and then blend it in with the curve mixers in the QTR driver.

The addition of magenta is to balance out some of the blue-green in the cyan/gray inks. There is very little extra density coming from the color inks to really change the overall gray curve, but you might want to take off the linearize= line and then do another 21 step measurement to linearize.

One way I approach this is to get the gray curve set with the spreadsheet correction curve template, and then add the toner inks and then linearize the final profile.

I am working on a method of being able to define a set of lab a and b values and a kind of reverse correction curve that will take into account the color of the paper base and the color of the gray inks, and then adjust the color accordingly and have it be precisely applied to be consistent across the whole tonal scale. I haven't been able to sit done and hash it all out yet, and It will take some spreadsheet trickery, but it *should* work.

Hope that helps,

RB

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