Digital BW, The Print

Thank you for clarifying that Roy.

So let us take a hypothetical situation:

We have a square with a value of 128 (mid value in 8 bit), and print that square. It will look up in the QTR curve for row 128 of each ink to lay down the inks.

If we have our image in 16 bits (total discrete levels is 2^16 = 65536), mid point is 23768. We cannot select this gray point in Photoshop color picker as far as I know. But I can imagine it exists is a 16 bit gray file. If we pick +1 from mid-point (or 23768 + 1 = 23769), how will QTR assign inks for this spot? Will it interpolate all inks values between 128 and 129 in the QTR curve description?

I know this does not have anything to do with K3 vs K7.

Shilesh

 

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Roy" <roy@...> wrote:
>
> Hi Shilesh,
> 
> Sorry but I have to disagree with this -- especially: QTR curves are 16-bit not 8-bit.   
> Yes there are 256 points but each one is a 16-bit value.
> > I think some people do not realize that if your image is 8 bit, there are 256 shades available,
> > and no interpolation between them is allowed. Even if the ink/paper system is capable of 
> > producing more shades than 256, it is never achieved in reality. The same applies even if 
> > your image is 16 bits, because QTR curves are described in 8 bit architecture.
> > 
> 
> I think the issue of 256 levels of gray is a misleading concept.  There are all these
> parts of the process that have specs of 8-bit or 256 values that it is very easy to fall 
> into the trap that the result print has to have 256 levels of gray.  But in real prints -- both
> digital and film -- the perception of gray is always an average of lots of pixels in the
> source and well as lots of dots of ink.   It's this averaging that fills in all the mid-grays
> between each of the 256 grays -- essentially making a continuous print.  
> 
> On a print I can pretty easily see the difference between steps that are 1 unit apart
> in 256 grays and 16-bit gradient across those same values.  (3800, K3 OEM inks & QTR)
> 
> So whether you are using K7, K3, or BO you will get more than 256 grays.  The difference
> is mainly seeing dots in the BO case -- the dark black dots on white paper have
> enough contrast that you see them with the naked eye.   I think the K3 LLK ink is
> light enough that you don't see them -- and I mean get up close and look critically.
> Most of my prints come from 4x5 film, tmax 100 and the grain from the film is more
> obvious than the grain from the dots.   The K7 light inks are lighter still and can
> stand more magnification before seeing the dots.   Tyler's article illustrates this,
> but the main thing I get from his scans is the dot resolution of the print is the most
> important factor -- 2880dpi is better than 1440dpi, and the silver dpi is still much
> better than that.
> 
> The things I think are important are using 16-bit for all editing from 16-bit scan
> or raw digital.  Use all the resolution you can.  QTR will use up to 720ppi, the
> Epson driver with use this on most printers if you select Finest Detail.
> To get great prints most things boil down to starting with the best image and
> knowing now to edit and get what you want it to look like.
> 
> ---------------
> 
> As far as what inks to use -- they are all good but there are tradeoffs and different
> amounts of work to get there.   Probably the biggest aesthetic decision is matte
> versus photo paper -- and within each category there are lots of choices.
> 
> K7 is great in that most is fixed and done for you.  K3 is great in that you have
> fine tuning control of color tone including split tones if you use QTR.  Glossy
> papers are often problematic and need GLOP but I find Harman Gloss Baryta
> does really well with Epson K3 inks straight as is.
> 
> Roy
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "shileshjani" <janishilesh@> wrote:
> >
> > I just read an interesting post by Jon Cone here:
> > 
> > http://www.piezography.com/PiezoPress/blog/piezography-technical/making-a-fine-piezography-print/
> > 
> > He says on page 2 of the pdf:
> > 
> > "Because Piezography with four or as many as seven distinct shades of ink can separate more tonal values than can the OEM three shade systems, it is important to start with very smooth image files that have a long tonal scale. Without going into mathematics and the virtues of using overlapping shades of Piezography inks rather than the interlinking shades of the OEM, the Piezography system produces tens of thousands more gray value combinations than can the OEM"
> > 
> > Is this true? When I arbitrarily open up a QTR curve for K7 inks published by Piezography, I find exactly 256 gray values, for each there is an assignment of inks to be used. But 256 (8 bit) gray values, no more no less.
> > 
> > To be provocatine, I say even a single black only (BO) system can print 256 shades gray. To be fair, the multiple ink set-up of K7 (or K3 for that matter) will produce each of the 256 shades with greater smoothness and overall finess than a BO print. Using the 8 bit QTR set-up, both BO and multi K will each produce 256 shades of gray.
> > 
> > I think some people do not realize that if your image is 8 bit, there are 256 shades available, and no interpolation between them is allowed. Even if the ink/paper system is capable of producing more shades than 256, it is never achieved in reality. The same applies even if your image is 16 bits, because QTR curves are described in 8 bit architecture.
> > 
> > In summary, on one single paper, K7, K3, or BO all produce AT MOST 256 shades of gray. It can be argued that using ABW on that same paper, you can actually produce many, many more shades of "near-neutral gray", but only 256 at a time. Again, ABW gets maligned in a manner that has no basis in fact.
> > 
> > Did I get this all wrong? Is there something to this that eludes my mind? Or is the ".........tens of thousands more gray value ....." just poetic waxing?
> > 
> > I concede there are some reasons to chose multi K systems like Piezography K7, but greater number of gray shades?
> > 
> > Shilesh
> >
>