QTR-Quadtone RIP

Hi Fred,

The nice thing about using Lab is that the ideal values just a straightline.
The L values are exactly what QTR linearizes to.  Densities are a more complicated
function.

If you do want to convert so you can compare dMax etc. these are the formulas:

first compute Y = luminance
Y = L/903.2               if L < 8
Y = ((L+16)/116)^3   if L >=8

second compute d = density
d = -log(Y)

typical whites are around L=95 to L=97
typical blacks on matte paper are around L=14 to L=17
  on photo paper more like L=4 to L=8

Roy


--- In QuadtoneRIP@yahoogroups.com, "fotofred2" <fotofred2@e...> wrote:
> Paul ...
> 
> Thanks for the input.  It is helpful, but I would also like to check
> the Dmax and the charts in Tom Moore's tutorial are based on density.
>  Once again, thanks for the input.
> 
> Fred Drury,
> Markland Imaging.
> 
> --- In QuadtoneRIP@yahoogroups.com, "Paul D. DeRocco" <pderocco@i...>
> wrote:
> > > From: fotofred2
> > >
> > > Many thanks for the reply Roy.  I found the write up you mentioned and
> > > have been successful scanning the 21 step random strip and saving as
> > > text file.  Now my problem is finding the Calc-Density program needed
> > > to convert my text file (Lab values, I presume) into density values.
> > 
> > Like he said, you don't have to do that. The QTR curve maker is equally
> > happy with density values or Lab values.
> > 
> > --
> > 
> > Ciao,               Paul D. DeRocco
> > Paul                mailto:pderocco@i...