Digital BW, The Print

Hi Tyler,

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Tyler Boley" 
<tyler@t...> wrote:
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "mike_nunan"
> <mike_nunan@h...> wrote:
> snip...
> > I didn't realise IP could use quadtone inksets or is that not 
what 
> > you meant?
> 
> Yes, it does, or did, support quad inksets and profiles were 
available.
> 

I guess not in the Lite version though, that probably explains why I 
wasn't aware of it.

<snip>
> > I suppose it 
> > would all depend upon the slope of the "worst" parts of the 
transfer 
> > curve, plus the number of bits of accuracy that are being used to 
> > represent the values being sent to the driver (out of interest, 
do 
> > know the answer to that second point?).
> 
> I believe out of necessity nearly all printer drivers have 16 bit
> internal ramping. Is that what you meant?
> But the problems lies less in individual channel linearity then it
> does with gray balance, and the manner the Epson driver does its 
GCR.

I would expect at least 16-bit precision in all internal calculations 
and data tables in the driver, probably 32-bit in fact. If you're 
talking about a RIP such as IP which works directly from the TIF 
file, then by using high-bit files you should also get 16-bit 
precision for the input values. I'm more suspicious regarding the 
precision used to pass values from PS via the OS to the Epson driver, 
especially since Adobe have been so tardy about implementing high-bit 
support even in the places where it's immediately obvious. It's this 
lack of precision that could make it impossible to compensate for non-
linearity upstream of the driver, whether by curves or profiling, 
without introducing banding. I appreciate that the grey balance is an 
issue too, but I'm taking the long view that it *can* be fixed via 
profiling provided you have enough precision to tweak the values 
accurately enough. I do realise that this is non-trivial to do (an 
understatement!) but the other problem is worse still.

> 
> snip
> >...Can you suggest any groups or forums where I could find some 
> > solid information about the different colour RIP options? <snip>
> 
> That's a problem, I've run across little objective comparison. Most
> user forums get a bit testy about it, we all spent so much on our
> software we tend to defend it too adamantly to justify the expense 
<G>.

Your candour is refreshing sir =)

I guess I'll just have to stick around here and pester you a bit 
more, sorry!

> 
> > Also, is there a decent 
> > free RIP out there, like QTR but for colour?
> 
> Not that I'm aware of, however there is an alpha version of 
GimpPrint
> that looks very promising. A lot of individual channel tuning and K
> generation controls. I'm dying to see if I can create an RGB tuned
> setting with it that behaves much better, then profile over it. The
> problem is that I haven't been able to make it print at all. When it
> does work though, it will still be a lot of work just to get it to 
the
> point of reasonalbe evaluation.
> If Adobe hadn't killed PressReady we'd have something to talk about.
> Even though it has no linearization or limiting, with good profiles 
it
> out-performs the Epson driver for color and was very affordable.
> Photoprinter version of many of these RIPs are coming out as
> manufacturers are recongizing the market, that are much more
> affordable, so there's hope. There's also scuttlebutt that Epson has
> been listening and may address some of the driver issues in coming 
models.

I think I'll wait to see what becomes of GimpPrint then. I'm 
reluctant to spend big money on a commercial RIP at this stage, and 
I'm not in a rush. I'm also in favour of using something that's a bit 
more open, so I can really know and control what's going on under the 
covers.

TTFN

-= mike =-