Digital BW, The Print

Ernst,

I think what you're saying relates to the difference between what I've heard
referred to (by Roy, I think) as "hardware" v. "software" linearization.  In
a properly written rip or driver, the different shades are generated by
different dot or dither patterns.  As such the file values are not altered
and the number of different levels of gray is not reduced.  However, if the
adjustments to get to the final ramp are made prior to the generation of the
dot pattern, the file values that are sent to that stage are altered and, if
all file values were being used, some grayscale steps and information are
lost.

The loss of information is minimized if the curve shape is mild, and, of
course, high bit depth minimizes the problem.

However, to the extent possible, to preserve as much information as
possible, we'd like as much of the work done with the dot/dither pattern as
possible.  For example, I recommend in the "EZ" approaches that the driver
controls first be use to achieve the best ramp.  Only when that is not quite
right do I recommend a curve, transfer function, or maybe ICC (if the ramp
toe problems can be fixed).  I think Roy recommends that the QTR curves be
as accurate as possible before one relies on an ICC linearization step.

Paul
www.PaulRoark.com 


> -----Original Message-----
> From: DigitalBlackandWhiteThePrint@yahoogroups.com
> [mailto:DigitalBlackandWhiteThePrint@yahoogroups.com] On Behalf Of Ernst
> Dinkla
> Sent: Monday, October 24, 2005 1:02 AM
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: Re: [Digital BW] ICC v. Transfer Function in Epson driver
> 
> If I were a RIP designer who could work from scratch with all
> the input over the years of lists like this I would look for a
> printer calibration method that would consider the native
> behaviour of the printer and what realistic standard was
> possible with that behaviour plus at the same time check what
> fitted color management on top of that standard best. If all
> the perceptual curves of different papers + BPC etc result in
> a space that isn't a too complex shape it must be possible to
> find the average 3D curve within that shape and use that as
> the calibration standard. Building the profiles on that should
> theoretically allow a better fit from the native behaviour of
> the printer up to the color management.
> 
> To give an analogy, if you have a metal cloth hanger with a
> shape you like to alter you could first start to make the wire
> frame straight and after that bend it to the shape you want.
> Measuring is easier then. You could also look whether the
> original shape has elements that come close to the desired
> shape and just alter the differences. Less bending needed but
> a more complex shape model to build on. Depends on the
> original shape and the desired shape which method is best.
> 
> If I were a RIP designer who had a RIP working as nice as QTR
> I would take care not to go on paths unknown. And Roy may even
> know that those paths are actually dead ends. For me it is an
> abstract model, Roy will now the numbers.
> 
>                     --
>            Ernst Dinkla
> 
> 
> www.pigment-print.com
> (         unvollendet         )
> 
> 
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