Digital BW, The Print

Thanks for the the reply Paul. For some reason i must have deleted the
.qidf file while unpacking the .zip file and had to tap into the .quad
file to see what you are doing, also making a mistake where LK and LLK
curves appeared.

We are almost at the and of our R&D after switching from wet to dry
darkroom. The last step is to choose the way to print. We started with
our own QTR curves, also hand made rather like you do, and 5 shades of
gray. Since the paper we will use is uncoated, we had to minimize the
ink put down and the  overlaps among the individual channels, to keep
the dot gain down. The results are beautiful, but we have considerable
 banding near the edge of the paper, due to the fact that the urves do
not allow more than two jets to fire at the same time.

Therefore, we started a  small project to compare the possible
printing methods:
1) Epson OEM (with the driver set in a way to work well with our gray
shades, basically same as you do)
2) Piezography through QTR
3)Your MK3 and Clayton's MK2
4) Our home made QTR curves
5) Your QTR curves


We disliked 1) quite a bit: dithering is not as smooth as QTR, with
larger dithering and very large dot gain. We reverse engineered the
OEM driver and observed the the partition curves are very wide. For
example, the lighter colors span from K=5% through 95%.   The printing
also occurs in a totally different way when compared to QTR. We sent
the same A4 print to the printer using QTR and the Epson driver,
intercepted the output and studied. The OEM driver start printing with
 small paper advancement, 0x11 units, then most of the print occurs
using 0x89 units and it ends again with 0x11 units. QTR, instead,
makes almost twice as many paper advancements, starting and ending
printing with 0x01 units steps, while most of the printing occurs with
0x45 units step advancements (1 unit = 1/360 inch).
We decided to give up on method 1)

Method 2) is very smooth. However it puts down too much non fully
black ink at K=100% and it lowers the DMax on the non coated paper.

Method 3) extremely beautiful: minimal banding on an epson R2400, with
Clayton's 2MK having a slight edge on 3MK for what graininess is
concerned. Dot gain is minimal. Since we use scanned analog film for
our work (no digital yet on that side) and uncoated fine art paper
(quite rough surface), we may indeed choose this method for the
production of our fine art prints (they will be 16"x22" and up in
size). The only downside is that it prints a bit too cold for our
taste on  our paper (it is OK for coated paper, however).

4) Is very beautiful: minimal dot gain, no grain and just slightly
warm as we like. However, lots of banding near the paper edges and,
sometimes, also in the middle of the print. The low redundancy in jets
firing makes the print quality sensitive to any small defect in jets.

5) We just started with this. It should be promising as your curves
seems to be the right compromise between 1) and 4). However, our
dilutions are quite different from yours and a quick adaptation of
your curves gave bad results. We use 100%, 20%, 5%, 3% and 1%
dilution. If you could help with some of your curves that might work
out, at least as a starting point, we will be very grateful. We
decided to use 1 less shade to keep a backup channel in 6-colors
printers, just in case somethings goes wrong with one of the channels.
Could not find a difference in print smoothness between 5 and 6 shades. 

BTW, we know how to reverse engineer the Epson partition and produce
equivalent QTR curves. In case of ABW in K3 printers, these
corresponds to read with a spectro more than 300 patches. If somebody
is interested in sharing some work to complete this R&D project, I can
send 6 files to be printed, each containing 51 patches that need to be
measured. The, I will translate those measurements into QTR curves.
Unfortunately, we do not have the time to do that as we nee to start
make prints for selling them very soon.

Thanks,

  Daniela
  
P.S I posted a question regarding hardproofing with QTR. Got no
answer. Anybody has ever tought at his problem in this newsgroup? may
be I have to post in the EpsonWideFormat group.





--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "pr_roark"
<pr_roark@...> wrote:
>
> Hi Daniela,
>  
> > ... Eb6-CondorBW-12-07.quad profile... looks
> > made for a K3 printer.
> 
> That QTR profile is for my 7500.  The *.qidf file indicates the printer 
> model.
> 
> > The curves for individual ink are very unconventional, 
> > with very large overlaps (although not as extreme as
> > in the Piezography curves).
> 
> I hand make curves as opposed to using the QTR semi-automatic 
> partitioning, although I sometimes start with that and then pull 
> the "skirts" out as needed to eliminate microbanding.  As I get into 
> the middle and dark midtones, I like to have 3 or 4 channels firing.  
> What I do not like, however is more than the MK firing at the 100% spot.
> 
> The Eboni-6 inkset is essentially the commercial version of Carbon-6.  
> Both have 6 different densities of ink.  The Eboni-6 uses dilutions 
> that relatively closely match the normal MK, UT/Piezo-C, UT-LC series 
> and the (PK omitted), LK, and LLK, with an "LLLK" added.  Each of these 
> series is based on a 30% dilution ratio, with LK being between MK and 
> UT-C.  The difference from Carbon-6 is that I made that series based on 
> an initial 1:2 (1 Eboni: 2 clear base) dilution and then a cascading 
> 1:1 dilutions for the remainder so that those without good scales could 
> mix it.  The 2 inksets are close enough that the profiles for one will 
> probably be within linearization reach of the other.
> 
> > Does it give you the usual problem of banding in the areas closest 
> > to the paper edge?
> 
> No.  In my experience that is a problem of desktop printers that use 
> 1.5 pl drops.  Eboni-6 and Carbon-6 on all of my non-1.5 pl printers 
> are exceptionally smooth all the way to the normal printer borders.
> 
> Carbon-6 is not recommended for 1.5 pl printers at all.  I'll try Eboni-
> 6 in the 1400 at some point, but since it does such a good job of 100% 
> Eboni with a simple QTR BO curve, I'm not sure how much need there is 
> for more.
> 
> While the curve you were looking at was for the QTR rip, my usual 
> workflow for the Eboni-6/Carbon-6 inksets is the Epson driver with an 
> ICC made with QTR's Create ICC-RGB.  I prefer to print from Photoshop 
> (Windows) in a "Color Managed" workflow.
> 
> Paul  
> www.PaulRoark.com
>