On Oct 14, 2015, at 2:34 AM, richard@richardboutwell.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
This is the interpolation formula I use. I remember this formula (or one similar) being described in one of the QTR Workflow write-ups but I don't recall exactly where off the top of my head.
(((Target density - Next Lower Density) / (Next Higher Density - Next Lower Density)) * (Patch# for next lower density + 5)) * cross over % of the next darker shade
That last bit of the "cross over percentage of the next darker shade" is what actually give you the value you put in think descriptor file. This first cross over point is easy because it is just 100. The next cross over point is also easy because the relative density of that shade is multiplied by 100% (the cross over point of the next darker shade). The cross over point of the next lighter shade is where it can be confusing because you need to multiply the relative density for that shade by the cross over point (as a percentage) of the next darker ink.
Hope that helps,
Richard Boutwell
Message
Re: [QuadtoneRIP] Help with a "bit of simple math".
2015-10-14 by Myron Gochnauer
I know that when I last used the process - - more than a year ago - - it wasn’t very difficult once I realized what was needed. But that understanding has faded with time, and as I read most of the current
thread I couldn’t quite get a grip on it again.
Having taught law for more than thirty years, I know that not everyone “gets it” the same way. If there are four ways of approaching an idea, you’d better use all four, and hope that by the time you’re
finished the lights have gone on in all of the eyes in your classroom. (Wishful thinking, probably!) Some people need only an appreciation of the general principle and the point of it, while others need a step-by-step recipe, and still others need a strongly
intuitive exemplar of the principle along with sample to experiment with. . . And everyone needs practice!
Myron