Digital BW, The Print

Roy,

 
> The .raw files are just saved in Photoshop RAW format.

My XP system with PS CS can save in Photoshop (*.psd); I'm not familiar with
the "RAW" version.

>  The files files
> just contain the data of an image file -- no headers or formatting of
> any kind. 

Is this something that is doable by Photoshop?


> I created 16-bit PS files that just had 256 pixels, one of
> each possible gray value.   You can then apply a .acv curve to it and
> save the result as a .raw.   The .raw will now contain the exact curve
> transformation which can then be used as a component of a QTR
> .quad file.

So, it acts as, in effect, a translation interface between the formats?

Have you looked at the text file that Picture Window (an *acv-compatible
application) allows to be edited?

>  So qacvraw takes one channel of a raw file and converts it
> from binary to text i.e. .quad format.   You can do grayscale with one
> channel or any number of channels 4,6,7,8 by just making the original
> PS file and .acv N channels.

It seems to me that the conversion is one .acv curve to one .quad (?) curve.
That sounds doable.

With the .acv curves, however, the Epson driver crossovers are in a black
box.  Unless the conversion program contained information about the Epson
driver cross-overs, I can not see how the program could map a .acv curve to
the 2 QTR curves that would be needed for the, for example, C - LC
crossover.

Then there is the lack of black ink crossover information.

Conversion might not be worth the work.

>  A minor issue is that PC and Mac store the
> bytes in opposite order.   


>The other program qacv extracts (x,y)
> coordinates out of a .acv file which can be connected and smoothed.

Unless there is crossover information & algorithms, this faces the same
problems.

I think the rips would benefit from having pre-made ink pairs that were
based on reverse-engineered, printer-specific printer crossovers, at least
for C-LC and M-LM.  One could put clear in alternating chambers and extract
this information rather easily.  The Black-LK-CMY cross-over sounds like a
bear.

Paul
www.PaulRoark.com 

__________________________________
 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Daniel Staver
> <daniel@p...> wrote:
> > The qacvraw program only works with special .RAW files that Roy created
> > while qacv works with Photoshop .ACV curves.
> >
> > The qacv program will output the curve points of the first channel in a
> > Photoshop curve as a set of x,y coordinates. Then you can use the qcurve
> > program to transform these coordinates into 256 16bit values. These
> > values can be used for one ink channel in QTR.
> >
> > In the latest, not yet released, version of QuadProfile and QTRgui we
> > support loading a Photoshop curve for any individual ink channel. If the
> > Photoshop curve has more than one channel the first will be used and the
> > others discarded.
> >
> > If you wanted to you could create a curve for every ink channel and
> > effectively bypass the entire profiling process in QTR and have full
> > manual control of every ink channel. A more reasonable approach would
> > perhaps to use this for special curves like GLOP curves where the curve
> > for the GLOP ink might have an unusual shape and you'd want full manual
> > control.
> >
> > You can also load a photoshop curve to modify a partitioned gray or
> > toner curve. This has always been supported.
> >
> > In addition to this you can manually enter curve points directly into
> > QTRgui instead of using the photoshop file format. Up to 50 curve points
> >   are supported.
> >
> > This works for all printers, the only difference is the amount of ink
> > channels you have available to work with.
> >
> > --
> > Daniel Staver
> > http://daniel.staver.no
> >
> > > Appendix 2 of Tom Moore's very useful Tutorial on making curves for
> QTR
> > > says, "quacvraw is a way to convert a photoshop curve into a
> QuadToneRIP
> > > curve.
> > >
> > > How do these work?
> > >
> > > What kinds of Photoshop curves are covered?
> > >
> > > Does it work for all Epson printers?  Hextone included?
> 
> 
> 
> 
> 
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