QTR-Quadtone RIP

--- In QuadtoneRIP@yahoogroups.com, "grangermacy" <grangermacy@...> wrote:

> In either case, how would you correctly specify/judge glop's use as an ink in QTR. Is there a good place to start?

Hello Granger, Glop usage has one caveat with QTR:  QTR will read RGB 255 or Gray 255 as paper white and not lay any ink down, so if you are going to use glop on any image you must add an adjustment layer that converts 255 to 254.  Easiest way is with Levels, go to the levels box and at output 255 change that to 254.  That will map all paper whites of 255 to 254 where the Glop will now print.

You can then add a CURVE= command after the UNUSED_INKS COMMANDS to activate the glop channel.  I have found on the inkset I use with Gold F Silk that very little glop is needed to prevent bronzing other than in the highlights.  Your mileage may differ.  Here is the curve I use and the syntax it would use if Y was the Glop channel.

CURVE_Y="0;81 7;9 100;0"""

As you can see CURVE_(X)=  Defines any channel.  You must precede with a quotation mark and separate the inputs from the outputs with a semicolon and insert single spaces between the defined points.  Do not insert spaces anywhere else and close with a set of triple quotation marks. 

This curve lays down 81% glop in the highest highlights and drops down fairly rapidly and by 30% mark has stopped laying down any glop.  If you open a New 16bit grayscale image in PS, add a curves layer, check PIgment Ink and then insert the above points you will be able to see the curve.

In QTR-CurveView with a MAC or with the Windows Curve Viewer you can open you .quad file and see how that curve is translated by QTR.