QTR-Quadtone RIP

Hi Sandy, 

I'm sure Richard can explain this better, but here is my practical experience.

It's the math. Gray_Curve values are given in percent. Richard's digital neg curve tool converts from Density to Lightness (L*), goes through some other fancy stuff, probably averaging to smooth any kinks out of the readings, and calculates the string of input;output pairs to paste into the Gray_Curve. Using L* rather than DEN provides visual linearity. That alone makes the whole process much easier. Sure wish I had known that years ago. 

I've been using PiezoDN myself for going on a year now, but when I make profiles for friends I use Richard's spreadsheet to make the Gray Curve for the first step, and the QTR-Linearize-Quad for the second step. On a couple of occasions I've needed to tweak one of the linearize numbers manually. 

With PiezoDN, there's probably even fancier math going on in the hidden part of the spreadsheet tools. There are no standard QTR text files. We begin with Master quad files that come with the download. QRT-Linearize-Quad is used with 129-step targets to perform the linearizations from L* readings. Two iterations is usually all it takes. 

I too was so used to zeroing my old X-rite 400 densitometer on the paper base that when I switched to taking LAB readings (or Density for that matter) with my SpyderPrint my instinct was to figure out how to zero it on the paper base - you can't, but it doesn't matter. The zero function on my densitometer actually stopped working a few years ago, but I found I could get Density measurements from the SpyderPrint, I just couldn't zero it on paper - only on the calibration base. Eventually I got used to it. Your i1 and its software may work differently though. 

Cheers,
Keith

Keith Schreiber
jkschreiber.com




> On Feb 18, 2017, at 7:21 PM, sanking@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> Richard,
> 
> Would you explain the rationale for not zeroing to paper base the density readings?
> 
> The targets for the iOne have a BEG and END zone that seems designed to do this, and I believe that I get much better correction curves when I do so, both with the spectro and with a densitometer. 
> 
> Sandy
> 
>